Synthesis and pharmacological evaluation of several ring-contracted amantadine analogs

Graphical abstract

Several bisnoradamantylamines and noradamantylamines have been synthesized and their antiviral, trypanocidal, NMDA receptor antagonist, and dopamine reuptake inhibitory activities have been studied.

Abstract

The synthesis of several (3-noradamantyl)amines, [(3-noradamantyl)methyl]amines, (3,7-dimethyl-1-bisnoradamantyl)amines, and [(3,7-dimethyl-1-bisnoradamantyl)methyl]amines is reported. They were evaluated against a wide range of viruses and one of them inhibited the cytopathicity of influenza A virus at a concentration similar to that of amantadine. Several of the new polycyclic amines show an interesting activity as NMDA receptor antagonists. A rimantadine analogue displayed significant trypanocidal activity. Moreover, to further characterize the pharmacology of these compounds, their effects on dopamine uptake were also assessed.

1. Introduction

1-Adamantylamine (amantadine) and (α-methyl-1-adamantyl)methylamine (rimantadine) have prophylactic and therapeutic activity in influenza A virus infections.¹ Related adamantane derivatives also show antiviral activity.² Adamantane derivatives are inexpensive, but resistance against the drugs develops readily and treatment is frequently complicated by central nervous system (CNS) side-effects. In fact, amantadine and its 3,5-dimethyl analogue memantine are NMDA receptor antagonists and are approved for the treatment of Parkinson’s and Alzheimer’s disease, respectively.³ Thus, the design of new amantadine-related anti-influenza agents without CNS side-effects is a highly desirable goal. Amantadine, rimantadine, memantine, and related polycyclic amines also possess trypanocidal activity (Fig. 1 ).⁴

Figure 1.

Amantadine, memantine, and rimantadine.

Biological activity has also been found in other polycyclic cage amines. For example, compounds 1−4 have anti-influenza activity,⁵ 5 is a MAO-B inhibitor,⁶ and 6 is a NMDA receptor antagonist (Fig. 2 ).⁷

Figure 2.

Polycyclic cage amines with biological activity.

For more than 20 years two of us (P.C. and S.V.) have worked on a project aimed at exploring the structure and the reactivity of noradamantane⁸ and bisnoradamantane derivatives.⁹ Up to now, our work on this topic has been done from a purely synthetic point of view. For example, we have developed several general entries to these skeletons. However, systematic studies directed towards the synthesis of biologically active noradamantane and bisnoradamantane derivative have not yet been carried out (Fig. 3 ).¹⁰

Figure 3.

Noradamantane and bisnoradamantane.

It is well known in medicinal chemistry that when drugs contain cyclic systems, it is generally worth synthesizing analogues where the ring is opened, expanded or contracted by one unit, because these analogues show similar activity to the parent compound.¹¹ Tricyclo[3.3.1.03, 7]non-3-ylamine [(3-noradamantyl)amine] and tricyclo[3.3.0.03, 7]oct-1-ylamine [(1-bisnoradamantyl)amine] may be viewed as ring contracted analogs of amantadine, featuring a skeleton with one and two carbon less than the model, respectively. For this reason, in this paper, we describe the preparation of a series of (3-noradamantyl)amines, (1-bisnoradamantyl)amines and related compounds as well as the results of their antiviral, trypanocidal, NMDA receptor antagonist, and dopamine reuptake inhibitory activities.

2. Results and discussion

2.1. Chemistry

Starting from the known amine 7,10, 12 we have prepared noradamantane amines 8−12 using classical methods in amine chemistry. Thus, reductive alkylation of 7 with several aromatic aldehydes afforded secondary amines 8a–f in moderate to high yields. Dimethylated derivative 10 was prepared as previously described in the literature.¹³ Monomethyl derivative 12 was synthesized from 8a by reductive alkylation followed by catalytic debenzylation in good overall yield. Finally, piperidine derivative 11 was prepared by alkylation of primary amine 7 with 1,5-dibromopentane in 51% yield (Scheme 1 ).

Scheme 1.

Reageants and conditions: (a) aldehyde, NaBH₃CN, acetic acid, methanol, 18 h; 92% for 8a, R = phenyl; 79% for 8b, R = 4-methoxyphenyl; 44% for 8c, R = 2-methoxyphenyl; 78% for 8d, R = 3-methoxyphenyl; 77% for 8e, R = 4-fluorophenyl; 63% for 8f, R = 2-thienyl; (b) formaldehyde, NaBH₃CN, acetic acid, acetonitrile, 4 h; 91%; (c) anhyd Et₃N, 1,5-dibromopentane, DMF, 60 °C, 26 h, 48%. (d) H₂ (1 atm), Pd/C, ethanol, 89%.

Starting from the known amide 13,¹⁴ a series of 3-(noradamantyl)methylamines were synthesized. Thus, reduction of amide 13 with LiAlH₄ followed by acidic work-up led to the hydrochloride of amine 14 in 90% yield. Reductive alkylation of 14 with benzaldehyde and NaCNBH₃ in methanol gave 15 in 77% yield. Reductive methylation of 15 followed by catalytic hydrogenation led to 19 in high yield. Reductive methylation of 14 with formic acid and formaldehyde furnished dimethyl derivative 17 in 68% yield. Finally, reaction of 14 with 1H-pyrazol-1-carboxamidine led to guanidine 18 in 84% yield (Scheme 2 ).

Scheme 2.

Reageants and conditions: (a) LiAlH₄, THF, reflux, 15 h, 90%; (b) benzaldehyde, NaBH₃CN, acetic acid, methanol, 18 h; 77%; (c) formaldehyde, NaBH₃CN, acetic acid, acetonitrile, 4 h; 96%; (d) formaldehyde, formic acid, diethyl ether, 80 °C, 10 h, 68%; (e) anhyd Et₃N, 1H-pyrazol-1-carboxamidine hydrochloride, acetonitrile, reflux, 6 h, 70%; (f) H₂ (1 atm), Pd/C, ethanol, 78%.

On the other hand, starting from the known acid 20,9g we have prepared amines 21−23, 25−28, and 30−36 using classical methods in amine chemistry. Although the synthesis of amine 21 from acid 20 was very low yielding using the classical Schmid’s or Curtius’ reactions (14% and 24% yield, respectively), application of the Yamada’s modification of the Curtius reaction allowed us to obtain and fully characterize the hydrochloride of amine 21 in 73% yield.

From this amine, reductive alkylation with benzaldehyde led to 22a in 60% yield. Similarly, reductive alkylation with 2-thiophenecarbaldehyde led to 22b in 69% yield. Reductive methylation of 22a followed by catalytic debenzylation furnished secondary amine 28 in high yield. Dimethylated derivative 26 was obtained in 83% yield by treating amine 21 with excess of formic acid and formaldehyde. Finally, dibenzylated compound 27 was prepared by double alkylation of 21 with benzyl chloride in 73% yield (Scheme 3 ).

Scheme 3.

Reageants and conditions: (a) Diphenylphosphorylazide, Et₃N, toluene, reflux, 3 h; then 6 N HCl, reflux, 24 h, 73%; (b) aldehyde, NaBH₃CN, AcOH, MeOH, 18 h; 60% for 22a, R = phenyl; 69% for 22b, R = 2-thienyl; (c) 37% aqueous formaldehyde, NaBH₃CN, AcOH, CH₃CN, 4 h, 88%; (d) MeLi, anhyd Et₂O, 0 °C to reflux, 16 h, 19%; (e) 37% aqueous formaldehyde, formic acid, Et₂O, 80 °C, 10 h, 83%; (f) benzyl chloride, NaI, K₂CO₃, CH₃CN, reflux, 24 h, 41%; (g) H₂, Pd/C, EtOH, 89%; (h) NH₂OH, NaOH, EtOH; then, LiAlH₄, Et₂O, reflux, 16 h, 43%.

Moreover, reaction of 20 with methyllithium gave ketone 24 in low yield. Reaction of 24 with hydroxylamine followed by reduction of the obtained oxime with LiAlH₄ gave amine 25, a compound that can be viewed as a ring contracted analog of the antiviral rimantadine (Scheme 3).

Finally, reduction of the amide 29, easily available from acid 20, with LiAlH₄ followed by acidic work-up gave the hydrochloride of amine 30 in 70% overall yield. Following a similar sequence of the previously used with amine 21, amines 31, 32, 33, and 36 were obtained in high yields. Piperidine derivative 34 was obtained by alkylation of amine 30 with 1,5-dibromopentane in 53% yield. Finally, reaction of 30 with 1H-pyrazol-1-carboxamidine led to guanidine 35 in 90% yield (Scheme 4 ).

Scheme 4.

Reageants and conditions: (a) SOCl₂, reflux, 2 h; then NH₄OH, CHCl₃, rt, 15 h, 84%; (b) LiAlH₄, THF, reflux, 15 h, 83%; (c) benzaldehyde, NaBH₃CN, AcOH, MeOH, rt, 18 h, 68% (d) 37% aqueous formaldehyde, NaBH₃CN, AcOH, CH₃CN, reflux, 4 h, 70%; (e) 37% aqueous formaldehyde, formic acid, Et₂O, 80 °C, 10 h, 61%; (f) Et₃N, 1,5-dibromopentane, DMF, 60 °C, 26 h, 53%; (g) Et₃N, 1H-pyrazol-1-carboxamidine, CH₃CN, reflux, 6 h, 90%; (h) H₂, Pd/C, EtOH, 38 atm, 85%.

The structure of all new compounds was confirmed by elemental analysis or accurate mass measurement, IR, ¹H NMR, ¹³C NMR, and mass spectral data.

2.2. Trypanocidal activity

The tsetse fly-transmitted protozoan parasite Trypanosoma brucei is the causative agent of Human African Trypanosomiasis (HAT). After a major upsurge of the disease in the late 1990s throughout many parts of sub-Saharan Africa, annual infections have now fallen to 70,000 as a result of major surveillance and treatment programmes.¹⁵ However, over 60 million people remain at risk, and in some areas death rates exceed those from HIV/AIDS and malaria. The drugs currently available to treat HAT require administration under medical supervision and are characterized by limited efficacy, toxicity, and resistance. For example, the arsenical drug melarsoprol, which is used to treat late stage disease, can result in a reactive encephalopathy which kills up to 10% of patients. In the absence of treatment, HAT is invariably fatal and new drugs are therefore urgently required. Recently, it was reported that the anti-influenza virus drug rimantadine was active in vitro against bloodstream form T. brucei, and that other aminoadamantane derivatives had enhanced activity.4, 16 To extend these observations, we have tested several new bisnoradamantanes and related compounds for activity against bloodstream form T. brucei.

The noradamantylamines and [(3-noradamantyl)methyl]amines described in this paper and the birnoradamantyl derivatives 21, 22a, 23, 27, 28, 32, 34, and 36 were found to have no significant activity against cultured bloodstream from T. brucei at concentrations up to 5 μg mL⁻¹. Compounds 26, 30, and 31 showed transient effect on growth at 5 μg mL⁻¹, but cells grew to normal density. Rimantadine analog 25 was the most active of the compounds tested and we established its IC₅₀ (6.02 ± 0.36 μM) and IC₉₀ (9.48 ± 2.64 μM) values. Amine 25 was found to be slightly more active than rimantadine (IC₅₀  = 7.04 ± 0.12 μM; IC₉₀  = 13.97 ± 1.68 μM) and at least 20 times more active than amantadine (IC₅₀  > 130 μM).

2.3. NMDA receptor antagonist activity

NMDA receptor antagonists are highly interesting compounds since these receptors have been involved in several neurodegenerative disorders. In fact, memantine is widely used in therapeutics to slow down the progression of Alzheimer’s disease.¹⁷

The activity of the different new polycyclic compounds was assayed on cerebellar granule neurons loaded with the calcium-sensitive probe Fura-2.¹⁸ Addition of glutamate or NMDA (100 μM) in the presence of glycine (10 μM) produced a robust and stable increase in intracellular calcium that was challenged with cumulative additions of the compounds to be tested. Although all the noradamantyl derivatives and several of the bisnoradamantyl compounds were able to inhibit calcium entry through NMDA receptors, none of the compounds was more potent than memantine against glutamate- or NMDA-induced calcium increase in cerebellar granule neurons (Table 1 ).

Table 1.

IC₅₀ (μM) values for selected polycyclic amines as NMDA antagonists.^a,b

Compound	Glutamate (100 μM)	NMDA (100 μM)
7	>500	92 ± 19
8c	>500	92 ± 30
8d	>500	87 ± 46
8f	384 ± 130	17 ± 4
9	>500	36 ± 2
10	>500	173 ± 4
11	>500	45 ± 4
12	205 ± 25	65 ± 15
15	>500	138 ± 16
16	>500	178 ± 25
18	453 ± 113	25 ± 8
19	>500	71 ± 6
21	274 ± 68	23 ± 2.2
22a	143 ± 62	70 ± 9.3c
22b	204 ± 13	80 ± 15
25	94 ± 29	37 ± 10
26	185 ± 69	153 ± 18
28	NEd	35 ± 3
30	>500	128 ± 39
31	NAe	47 ± 15c
32	NA	160 ± 24c
35	104 ± 31	7.1 ± 0.4
Amantadine	358 ± 130	92 ± 29
Memantine	55 ± 12	1.5 ± 0.1

^aFunctional data were obtained from primary cultures of cerebellar granule neurons using the method described in Section 4 by measuring the intracellular calcium concentration. Cells were challenged with glutamate (2nd column) or NMDA (3rd column) as indicated. Data shown are means ± SEM of at least three separate experiments carried out on three diferent batches of cultured cells.

^bCompounds 8a, 8b, 8e, 14, 17, 23, 33, 34, and 36 were found to have low potency as NMDA receptor antagonists (IC₅₀ > 200 mM), while compound 27 was found not active at the highest concentration tested.

^cOnly 60% maximal inhibition due to insolubility in the assay buffer.

^dNE, not evaluated.

^eNA, not active at the highest concentration tested.

In general, the bisnoradamantane derivatives are more potent as NMDA receptor antagonists than the noradamantane amines. For example, amine 21 is 4 times more potent as NMDA receptor antagonist than 3-noradamantylamine, 7, and the guanidine derivative 35 is 3.5 times more potent than its corresponding noradamantyl analog, 18.

Bisnoradamantylamines were usually more active than their corresponding (bisnoradamantyl)methylamine analogs as exemplified by the pairs 21/30, 26/33, and 28/36, and alkyl substitution causes a reduction in the potency (e.g., series 21/28/26 or 30/36/33). The guanidine derivative 35 was the more potent compound, being 10 times more potent than amantadine and 5 times less potent than memantine. Attempts to synthesize a guanidine derivative from 21 were not successful.

2.4. Antiviral activity

None of the synthesized compounds was found to have antiviral activity against the enveloped DNA viruses herpes simplex virus (type 1 or type 2) or vaccinia virus; the enveloped RNA viruses feline coronavirus, parainfluenza-3 virus, respiratory syncytial virus, vesicular stomatitis virus, sindbis virus, or Punta Toro virus; or the non-enveloped RNA viruses Coxsackievirus B4 and Reovirus-1. In the influenza virus assays, only compounds 7 and 14, two primary amines, displayed reasonable activity against the influenza A/H1N1 and A/H3N2 subtypes, secondary and tertiary amines were not active (Table 2 ). The antiviral data obtained by microscopy were confirmed by a colorimetric cell viability assay (data not shown). The highest selectivity was noted with compound 7 tested against the A/H3N2 subtype. As anticipated, all compounds proved to be inactive against influenza B virus, which is known to be insensitive to amantadine and rimantadine.

Table 2.

Antiviral activity against influenza virus in MDCK cells.

Compound	Antiviral EC50a in μM			Cytotoxicity (MCCb in MDCK)
	A/H1N1	A/H3N2	B
7	196 ± 109	26.5 ± 22.5	NAc	>575
14	36 ± 11	52 ± 16	NA	>530
Amantadine	77 ± 21	2.7 ± 1.1	NA	>100
Rimantadine	29 ± 18	0.85 ± 1.1	NA	>100

^aEC₅₀: compound concentration producing 50% antiviral effect, as determined by microscopic scoring of the virus-induced cytopathic effect.

^bMCC, minimum cytotoxic concentration, or compound concentration causing minimal changes in cell morphology.

^cNA, not active at subtoxic concentrations, or at the highest concentration tested.

2.5. Dopamine

It is known that amantadine increases extracellular dopamine levels by antagonism of the NMDA receptor,¹⁹ although the exact mechanism has not been fully elucidated. As several of our new amines showed NMDA receptor antagonist activity with IC₅₀ similar or even lower than amantadine, we have determined their effect on [³H]dopamine uptake in rat striatal synaptosomes (Table 3 ). At the concentration tested (100 μM), several of the compounds were able to inhibit [³H]dopamine uptake in some manner, showing similar values of inhibition than amantadine or memantine. However, it seems that no correlation exists with their potency as antagonists at the NMDA receptor. Probably, other mechanisms are being involved in the regulation of dopamine release, like different activities at D₂ receptors or through inhibition at the dopamine transporter.

Table 3.

Effect of compounds on dopamine uptake (at 100 μM).

Compound	[3H]Dopamine uptake, % control ± SEM (n = 3)
7	84.9 ± 1.6
8a	31.7 ± 6.1
8b	63.9 ± 4.2
8c	58.3 ± 2.9
8d	45.8 ± 0.5
8e	81.1 ± 8.5
8f	47.7 ± 4.2
9	47.2 ± 3.4
10	71.3 ± 2.6
11	68.5 ± 2.3
12	65.2 ± 4.8
14	50.1 ± 3.5
15	57.9 ± 4.6
16	45.0 ± 2.5
17	62.5 ± 1.2
18	118.7 ± 7.3
19	76.3 ± 3.1
21	54.8 ± 14.3
25	72.2 ± 10.9
26	75.2 ± 6.9
27	74.3 ± 5.3
28	74.6 ± 6.6
30	39.1 ± 2.1
34	39.8 ± 7.4
36	57.3 ± 6.7
Amantadine	47.4 ± 2.0
Memantine	53.7 ± 2.6

3. Conclusions

In summary, we have synthesized and fully characterized several (3-noradamantyl)amines, (3-noradamantyl)methylamines, (3-bisnoradamantyl)amines, and (3-bisnoradamantyl)methylamines. Although these compounds were less potent than memantine against NMDA-induced calcium increase in cerebellar granule neurons, several compounds were more potent than amantadine, the bisnoradamantane amines being more potent than the corresponding noradamantane amines. Interestingly, none of those compounds showed antiviral activity, while compound 14, that displayed reasonable activity against the influenza A/H1N1 and A/H3N2 subtypes, showed no NMDA receptor antagonist activity. Moreover, none of the compounds were significantly more potent, at the tested concentration, than amantadine or memantine as inhibitors of the dopamine uptake.

Amantadine displays both anti-influenza activity and NMDA receptor antagonism. As selectivity is usually highly desirable in drugs, the amines herein reported open the way for the design of new aminopolycyclic compounds with selective anti-influenza or NMDA receptor antagonist activity.

Interestingly, amine 25, that is 2.5 times more potent than amantadine as NMDA receptor antagonist, also displayed trypanocidal activity, being slightly more active than rimantadine and at least 21 times more active than amantadine.

Guanidine 35 is a polycyclic cage compound with selective NMDA receptor antagonist activity (IC₅₀  = 7.1 μM) without antiviral and trypanocidal activities.

The synthesis and pharmacological evaluation of more polycyclic cage amines is in progress to reach more potent and selective derivatives.

4. Experimental

4.1. Chemistry

4.1.1. General

Melting points were determined in open capillary tubes. Unless otherwise stated, NMR spectra were recorded in CD₃OD in the following spectrometers: ¹H NMR (500 MHz), ¹³C NMR (100.6 MHz). Chemical shifts (δ) are reported in ppm related to internal tetramethylsilane (TMS). Assignments given for the NMR spectra are based on DEPT, COSY ¹H/¹H, and HETCOR ¹H/¹³C (HSQC and HMBC sequences for one bond and long range ¹H/¹³C heterocorrelations, respectively) and NOESY experiments for selected compounds. For the MS and GC/MS analyses the sample was introduced directly or through a gas chromatograph. For GC/MS analyses a 30-m column [5% diphenyl–95% dimethylpolysiloxane, conditions: 10 psi, initial temperature: 35 °C (2 min), then heating at a range of 8 °C/min till 300 °C, then isothermic at 300 °C] was used. The electron impact (70 eV) or chemical ionization (CH₄) techniques were used. Only significant ions are given: those with higher relative ratio, except for the ions with higher m/z values. Accurate mass measurements were obtained using ESI technic. Absorption values in the IR spectra (KBr) are given as wave-numbers (cm⁻¹). Column chromatography was performed on silica gel 60 Å (35–70 mesh). For the thin-layer chromatography (TLC) aluminum-backed sheets with silica gel 60 F₂₅₄ were used and spots were visualized with UV light and/or 1% aqueous solutions of KMnO₄.

4.1.2. N-Benzyl(tricyclo[3.3.1.0^3,7]non-3-yl)amine hydrochloride (8a·HCl)

To a solution of 7·HCl (600 mg, 3.46 mmol) in MeOH (10 mL), NaBH₃CN (95%, 445 mg, 6.72 mmol), AcOH (0.3 mL), and benzaldehyde (0.5 mL, 4.92 mmol) were added and the mixture was stirred at room temperature for 2 h. An additional portion of NaBH₃CN (95%, 220 mg, 3.33 mmol) and benzaldehyde (0.25 mL, 2.46 mmol) were added, the mixture was stirred at room temperature overnight and concentrated to dryness. Water (20 mL) was added to the residue, the suspension was basified with 1 N NaOH and was extracted with EtOAc (3× 10 mL). The combined organic extracts were washed with brine (2× 10 mL), dried with anhyd Na₂SO₄, filtered, and concentrated in vacuo. The residue was taken in EtOAc and the amine 8a was precipitated as its hydrochloride (839 mg, 92% yield) by adding an excess of Et₂O·HCl. The analytical sample of 8a·HCl was obtained by crystallization from MeOH, mp >300 °C (dec). IR: 2942, 2757, 2656, 2600, 2428, 2363, 2340, 1458, 1425, 1331, 728, 694 cm⁻¹. ¹H NMR 1.64 (dquint, J  = 13.2 Hz, J′ = 2.5 Hz, 1H, 9-H_syn), 1.73 (dd, J  = 11.0 Hz, J′ = 2.5 Hz, 2H, 6(8)-H_α], 1.75 (overlapped dm, 1H, 9-H_anti), 2.04 [m, 2H, 6(8)-H_β], 2.10 [m, 2H, 2(4)-H_β], 2.14 [dd, J  = 10.5 Hz, J′ = 2.0 Hz, 2H, 2(4)-H_α], 2.45 [broad s, 2H, 1(5)-H], 2.48 [tt, J  = 7.0 Hz, J′ = 1.5 Hz, 1H, 7-H], 4.21 (s, 2H, CH ₂C₆H₅), 7.44−7.50 [complex signal, 3H, Ar-3(5)-H, and Ar-4-H], 7.55 [m, 2H, Ar-2(6)-H]. ¹³C NMR 35.0 (CH₂, C9), 38.8 [CH, C1(5)], 43.66 (CH, C7), 43.73 [CH₂, C6(8)], 46.3 [CH₂, C2(4)], 48.8 (CH₂, CH₂–C₆H₅), 71.9 (C, C3), 130.3 [CH, Ar-C3(5)], 130.6 (CH, Ar-C4), 130.9 [CH, Ar-C2(4)], 133.2 (C, Ar-C1). MS (EI), m/z (%): 228 ([M+H]⁺, 30), 227 (20), 185 ([M−C₃H₆]^{• +}, 83), 184 (52), 91 (C₇H₇ ⁺, 100). Anal. Calcd for C₁₆H₂₁N·HCl (263.81): C, 72.85; H, 8.41; N, 5.31; Cl, 13.44. Found: C, 72.90; H, 8.31; N, 5.18; Cl, 13.96.

4.1.3. N-(4-Methoxybenzyl)(tricyclo[3.3.1.0^3,7]non-3-yl)amine hydrochloride (8b·HCl)

From 7·HCl (173 mg, 1.00 mmol), NaBH₃CN (95%, 142 mg, 2.15 mmol), AcOH (0.3 mL), and 4-methoxybenzaldehyde (0.18 mL, 1.48 mmol) in MeOH (7 mL) and following the above procedure, 8b·HCl was obtained (233 mg, 79% yield). The analytical sample of 8b·HCl was obtained by crystallization from 2-propanol, mp >300 °C (dec). IR: 2926, 2794, 2751, 2716, 2678, 2592, 2578, 2443, 1613, 1588, 1514, 1460, 1440, 1333, 1306, 1272, 1248, 1178, 1040, 993, 826, 814, 767 cm⁻¹. ¹H NMR 1.63 (dquint, J  = 13.1 Hz, J′ = 2.5 Hz, 1H, 9-H_syn), 1.72 [dd, J  = 11.5 Hz, J′ = 2.2 Hz, 2H, 6(8)-H_α], 1.74 (overlapped dm, 1H, 9-H_anti), 2.00–2.09 [complex signal, 4H, 2(4)-H_β, and 6(8)-H_β], 2.12 [dd, J  = 10.5 Hz, J′ = 2.2 Hz, 2H, 2(4)-H_α], 2.43–2.46 [complex signal, 3H, 1(5)-H, and 7-H], 3.82 (s, 3H, OCH₃), 4.14 (s, 2H, CH ₂–C₆H₅), 7.01 [m, 2H, Ar-3(5)-H], 7.45 [m, 2H, Ar-2(6)-H]. ¹³C NMR (75.4 MHz) 35.0 (CH₂, C9), 38.8 [CH, C1(5)], 43.7 (CH, C7), 43.7 [CH₂, C6(8)], 46.4 [CH₂, C2(4)], 48.1 (CH₂, CH₂–C₆H₅), 55.9 (CH₃, OCH₃), 71.6 (C, C3), 115.6 [CH, Ar-C3(5)], 124.9 (C, Ar-C1), 132.4 [CH, Ar-C2(6)], 162.1 (C, Ar-C4). MS (EI), m/z (%): 257 (M^{• +}, 38), 214 ([M−C₃H₇]⁺, 48), 121 [(CH₃OC₆H₄CH₂)⁺, 100]. Anal. Calcd for C₁₇H₂₃NO·1.05 HCl (295.7): C, 69.06; H, 8.20; N, 4.74; Cl, 12.59. Found: C, 68.69; H, 8.19; N, 4.70; Cl, 12.73.

4.1.4. N-(2-Methoxybenzyl)(tricyclo[3.3.1.0^3,7]non-3-yl)amine hydrochloride (8c·HCl)

From 7·HCl (173 mg, 1.00 mmol), NaBH₃CN (95%, 142 mg, 2.15 mmol), AcOH (0.3 mL), and 2-methoxybenzaldehyde (0.18 mL, 1.46 mmol) in MeOH (7 mL) and following the procedure described for 8a, 8c·HCl was obtained (128 mg, 44% yield). The analytical sample of 8c·HCl was obtained by crystallization from 2-propanol, mp 262−263 °C. IR: 2956, 2921, 2717, 2678, 2582, 2433, 1605, 1584, 1496, 1466, 1456, 1446, 1435, 1332, 1292, 1253, 1121, 1050, 1031, 771, 752 cm⁻¹. ¹H NMR 1.63 (dquint, J  = 13.4 Hz, J′ = 2.5 Hz, 1H, 9-H_syn), 1.73 [dd, J  = 11.0 Hz, J′ = 2.5 Hz, 2H, 6(8)-H_α], 1.76 (overlapped dm, 1H, 9-H_anti), 1.99–2.05 [complex signal, 2H, 6(8)-H_β], 2.07 [dm, J  = 10.5 Hz, 2H, 2(4)-H_β], 2.14 [dd, J  = 10.5 Hz, J′ = 2.5 Hz, 2H, 2(4)-H_α], 2.44 [broad s, 2H, 1(5)-H], 2.49 (tt, J  = 6.7 Hz, J′ = 1.7 Hz, 1H, 7-H), 3.94 (s, 3H, OCH₃), 4.19 (s, 2H, CH ₂C₆H₅), 7.03 (td, J  = 7.7 Hz, J′ = 1.0 Hz, 1H, Ar-5-H), 7.11 (d, J  = 8.5 Hz, 1H, Ar-3-H), 7.42 (dd, J  = 7.2 Hz, J′ = 1.7 Hz, 1H, Ar-6-H), 7.46 (ddd, J  = 8.4 Hz, J′ = 7.4 Hz, J′′ = 1.6 Hz, 1H, Ar-4-H). ¹³C NMR 35.0 (CH₂, C9), 38.7 [CH, C1(5)], 43.5 (CH, C7), 43.8 [CH₂, C6(8)], 44.4 (CH₂, CH₂C₆H₅), 46.3 [CH₂, C2(4)], 56.1 (CH₃, OCH₃), 71.9 (C, C3), 112.1 (CH, Ar-C3), 121.1 (C, Ar-C1), 122.0 (CH, Ar-C5), 132.6 (CH, Ar-C6), 132.7 (CH, Ar-C4), 159.4 (C, Ar-C2). MS (EI), m/z (%): 257 (M^{• +}, 35), 214 ([M−C₃H₇]⁺, 57), 121 ([CH₃OC₆H₄CH₂]⁺, 100), 91 (55). Anal. Calcd for C₁₇H₂₃NO·HCl (293.83): C, 69.49; H, 8.23; N, 4.77; Cl, 12.07. Found: C, 69.21; H, 8.29; N, 4.80; Cl, 12.32.

4.1.5. N-(3-Methoxybenzyl)(tricyclo[3.3.1.0^3,7]non-3-yl)amine hydrochloride (8d·HCl)

From 7·HCl (173 mg, 1.00 mmol), NaBH₃CN (95%, 142 mg, 2.15 mmol), AcOH (0.3 mL), and 3-methoxybenzaldehyde (0.18 mL, 1.45 mmol) in MeOH (7 mL) and following the procedure described for 8a, 8d·HCl was obtained (228 mg, 78% yield). The analytical sample of 8d·HCl was obtained by crystallization from 2-propanol, mp >257 °C (dec). IR: 3002, 2923, 2873, 2792, 2734, 2708, 2678, 2585, 2446, 1606, 1599, 1588, 1494, 1460, 1437, 1331, 1306, 1272, 1256, 1174, 1035, 851, 794 cm⁻¹. ¹H NMR 1.63 (dquint, J  = 13.3 Hz, J′ = 2.6 Hz, 1H, 9-H_syn), 1.72 (broad d, J  = 11.0 Hz, 2H, 6(8)-H_α), 1.74 (overlapped dm, 1H, 9-H_anti), 2.05 [m, 2H, 6(8)-H_β], 2.09−2.14 [complex signal, 4H, 2(4)-H_α, and 2(4)-H_β], 2.44 [broad s, 2H, 1(5)-H], 2.50 (tt, J  = 1.6 Hz, J′ = 6.7 Hz, 1H, 7-H), 3.84 (s, 3H, OCH₃), 4.18 (s, 2H, CH ₂C₆H₅), 7.00 (ddd, J  = 8.5 Hz, J′ = 2.5 Hz, J′′ = 1.0 Hz, 1H, Ar-4-H), 7.12 (dt, J  = 7.5 Hz, J′ = 1.0 Hz, 1H, Ar-6-H), 7.17 (t, J  = 2.5 Hz, 1H, Ar-2-H), 7.38 (pseudo t, J  = 8.0 Hz, 1H, Ar-5-H). ¹³C NMR 35.0 (CH₂, C9), 38.8 [CH, C1(5)], 43.66 (CH, C7), 43.72 [CH₂, C6(8)], 46.3 [CH₂, C2(4)], 48.7 (CH₂, CH₂C₆H₅), 55.9 (CH₃, OCH₃), 71.9 (C, C3), 116.0 (CH, Ar-C4), 116.4 (CH, Ar-C2), 122.8 (CH, Ar-C6), 131.5 (CH, Ar-C5), 134.5 (C, Ar-C1), 161.8 (C, Ar-3). MS (EI), m/z (%): 258 ([M+H]⁺, 31), 257 (M^{• +}, 25], 215 ([M−C₃H₆]^{• +}, 55), 214 ([M−C₃H₇]⁺, 41), 121 ([CH₃OC₆H₄CH₂]⁺, 100], 91 (17). Anal. Calcd for C₁₇H₂₃NO·1.1HCl·0.1H₂O (299.28): C, 68.23; H, 8.18; N, 4.68; Cl, 13.03. Found: C, 68.13; H, 8.34; N, 4.69; Cl, 12.91.

4.1.6. N-(4-Fluorobenzyl)(tricyclo[3.3.1.0^3,7]non-3-yl)amine hydrochloride (8e·HCl)

From 7·HCl (150 mg, 0.86 mmol), NaBH₃CN (95%, 125 mg, 1.89 mmol), AcOH (0.3 mL), and 4-fluorobenzaldehyde (0.14 mL, 1.31 mmol) in MeOH (8 mL) and following the procedure described for 8a, 8e·HCl was obtained (186 mg, 77% yield). The analytical sample of 8e·HCl was obtained by crystallization from ethyl acetate, mp >300 °C (dec). IR: 2947, 2920, 2797, 2754, 2580, 2446, 1604, 1590, 1514, 1457, 1440, 1429, 1334, 1232, 1163, 1127, 830, 778 cm⁻¹. ¹H NMR 1.64 (dquint, J  = 13.2 Hz, J′ = 2.5 Hz, 1H, 9-H_syn), 1.73 (dd, J  = 11.0 Hz, J′ = 2.5 Hz, 2H, 6(8)-H_α), 1.76 (overlapped dm, 1H, 9-H_anti), 2.00-2.06 [m, 2H, 6(8)-H_β], 2.08 [dm, J  = 10.5 Hz, 2H, 2(4)-H_β], 2.13 [dd, J  = 10.2 Hz, J′ = 1.7 Hz, 2H, 2(4)-H_α], 2.45 [broad s, 2H, 1(5)-H], 2.47 [overlapped tt, J  = 6.7 Hz, J′ = 1.7 Hz, 1H, 7-H], 4.21 (s, 2H, CH ₂–C₆H₅), 7.22 (tt, J  = 8.7 Hz, J′ = 2.2 Hz, 2H, Ar-3(5)-H), 7.58 (m, 2H, Ar-2(6)-H). ¹³C NMR 35.0 (CH₂, C9), 38.8 [CH, C1(5)], 43.67 (CH, C7), 43.72 [CH₂, C6(8)], 46.3 [CH₂, C2(4)], 48.0 (CH₂, CH₂–C₆H₅), 71.8 (C, C3), 117.1 [CH, d, ² J _CF  = 22.4 Hz, Ar-C3(5)], 129.3 (C, Ar-C1), 133.3 [CH, d, ³ J _CF  = 9.0 Hz, Ar-C2(6)], 164.8 (C, d, ¹ J _CF  = 247.7 Hz, Ar-C4). MS (EI), m/z (%): 245 (M^{• +}, 32), 203 (16), 202 ([M−C₃H₇]⁺, 100), 109 ([FC₆H₄CH₂]⁺, 100), 106 (20). Anal. Calcd for C₁₆H₂₀NF·1.1HCl·0.33H₂O (291.45): C, 65.94; H, 7.53; N, 4.81; Cl, 13.38; F, 6.52. Found: C, 66.01; H, 7.67; N, 4.83; Cl, 13.31; F, 6.34.

4.1.7. N-(2-Thenyl)(tricyclo[3.3.1.0^3,7]non-3-yl)amine hydrochloride (8f·HCl)

From 7·HCl (150 mg, 0.86 mmol), NaBH₃CN (95%, 125 mg, 1.89 mmol), AcOH (0.3 mL), and 2-thiophenecarbaldehyde (0.12 mL, 1.37 mmol) in MeOH (8 mL) and following the procedure described for 8a, 8f·HCl was obtained (145 mg, 66% yield). The analytical sample of 8f·HCl was obtained by crystallization from EtOAc, mp 278 °C (dec). IR: 2939 2917, 2790, 2747, 2442, 1589, 1457, 1440, 1429, 1334, 1256, 1194, 1126, 984, 854, 695 cm⁻¹. ¹H NMR 1.64 (dquint, J  = 13.0 Hz, J′ = 2.5 Hz, 1H, 9-H_syn), 1.73 (dd, J  = 11.0 Hz, J′ = 2.5 Hz, 2 H, 6(8)-H_α), 1.75 (overlapped dm, 1H, 9-H_anti), 2.00–2.05 [m, 2H, 6(8)-H_β], 2.07 [dm, J  = 10.0 Hz, 2H, 2(4)-H_β], 2.12 [dd, J  = 10.0 Hz, J′ = 2.5 Hz, 2H, 2(4)-H_α], 2.44 [broad s, 2H, 1(5)-H], 2.46 (overlapped tt, J  = 8.5 Hz, J′ = 2.0 Hz, 1H, 7-H), 4.46 (s, 2H, CH ₂C₄H₃S), 7.12 (dd, J  = 5.0 Hz, J′ = 4.0 Hz, 1H, Ar-4-H), 7.34 (dm, J  = 3.5 Hz, 1H, Ar-3-H), 7.57 (dd, J  = 5.0 Hz, J′ = 1.0 Hz, 1H, Ar-5-H). ¹³C NMR 35.0 (CH₂, C9), 38.8 [CH, C1(5)], 42.6 (CH₂, CH₂C₄H₃S), 43.7 (CH, C7), 43.7 [CH₂, C6(8)], 46.2 [CH₂, C2(4)], 71.8 (C, C3), 128.7 (CH, Ar-C4), 129.2 (CH, Ar-C5), 131.5 (CH, Ar-C3), 134.0 (C, Ar-C1). MS (EI), m/z (%): 233 (M^{• +}, 56), 190 ([M−C₃H₇]⁺, 78), 106 (45), 97 [(C₄H₃SCH₂)⁺, 100]. Anal. Calcd for C₁₄H₁₉NS·1.05HCl·0.25H₂O (276.17): C, 60.89; H, 7.50; N, 5.07; S, 11.61; Cl, 13.48. Found: C, 60.99; H, 7.59; N, 5.09; S, 11.28; Cl, 13.49.

4.1.8. N-Benzyl-N-methyl(tricyclo[3.3.1.0^3,7]non-3-yl)amine hydrochloride (9·HCl)

To a solution of 8a·HCl (395 mg, 1.5 mmol) in acetonitrile (10 mL), formaldehyde (1.18 mL, 37% wt. in water solution, 15 mmol), and NaBH₃CN (95%, 238 mg, 4.28 mmol) were added. The mixture was stirred for 30 min at room temperature, AcOH (0.3 mL) was added and the mixture was stirred at room temperature for 2 h. An additional portion of NaBH₃CN (95%, 283 mg, 4.28 mmol) was added and the mixture was further stirred at room temperature for 2 h. The mixture was concentrated to dryness, 2 N NaOH (20 mL) was added and the suspension was extracted with CH₂Cl₂ (3× 20 mL). The combined organic phases were washed with H₂O (2× 20 mL), dried with anhyd Na₂SO₄, filtered, and concentrated in vacuo. The residue was taken in EtOAc and the amine 9 was precipitated as its hydrochloride (327 mg, 91% yield) by adding an excess of Et₂O·HCl. The analytical sample of 9·HCl was obtained by crystallization from 2-propanol, mp 258−259 °C (dec). IR: 3042, 2927, 2872, 2850, 2608, 2553, 2520, 2487, 2472, 2391, 1498, 1458, 1405, 1332, 994, 748, 696 cm⁻¹. ¹H NMR 1.64 (dquint, J  = 13.5 Hz, J′ = 2.6 Hz, 1H, 9-H_syn), 1.78 (dd, J  = 11.5 Hz, J′ = 3.0 Hz, 2 H, 6(8)-H_α), 1.79 (dm, J  = 13.5 Hz, 1H, 9-H_anti), 2.09–2.29 [complex signal, 6 H, 6(8)-H_β, 2(4)-H_α, and 2(4)-H_β], 2.50 [broad s, 2 H, 1(5)-H], 2.73 (s, 3 H, N-CH₃), 2.75 (tt, J  = 7.0 Hz, J′ = 2.0 Hz, 1H, 7-H), 4.09 (d, J  = 11.7 Hz, 1H) and 4.60 (d, J  = 11.7 Hz, 1H) (CH ₂–C₆H₅), 7.49–7.53 [complex signal, 3 H, Ar-3(5)-H and Ar-4-H], 7.59 [m, 2 H, Ar-2(6)H]. ¹³C NMR 35.2 (CH₂, C9), 36.5 (CH₃, NCH₃), 38.8 [CH, C1(5)], 42.8 (CH, C7), 43.8 [CH₂, C6(8)], 44.4 (broad signal, CH₂) and 45.4 (broad signal, CH₂) (C2 and C4), 58.1 (CH₂, CH₂C₆H₅), 79.9 [C, C3), 130.3 (CH, Ar-C3(5)], 131.1 (CH, Ar-C4), 131.3 (C, Ar-C1), 132.4 [C, Ar-C2(6)]. MS (EI), m/z (%): 241 (M^{• +}, 70), 199 (25), 198 ([M−C₃H₇]⁺, 100), 185 (40), 120 (17), 91 (96). Anal. Calcd for C₁₇H₂₃N·HCl (277.84): C, 73.49; H, 8.71; N, 5.04; Cl, 12.76. Found: C, 73.61; H, 8.74; N, 5.04; Cl, 12.99.

4.1.9. N-(Tricyclo[3.3.1.0^3,7]non-3-yl)piperidine hydrochloride (11·HCl)

To a solution of 7·HCl (173 mg, 1.00 mmol) in DMF (2.5 mL), anhyd Et₃N (0.4 mL, 2.9 mmol) was added and the suspension was stirred at room temperature for 2 h. 1,5-Dibromopentane (0.17 mL, 1.2 mmol) was added and the mixture was heated at 60 °C for 26 h. To the cold mixture, water (15 mL) was added and the solution was washed with EtOAc (3× 10 mL). The aqueous phase was basified with 2 N NaOH (5 mL) and extracted with ethyl acetate (3×10 mL). The combined organic extracts were washed with water (3× 10 mL), dried with anhyd Na₂SO₄, filtered and excess of Et₂O·HCl was added. The solution was concentrated in vacuo to dryness to give 11·HCl (117 mg, 48% yield). The analytical sample of 11·HCl was obtained by crystallization from MeOH/Et₂O, mp >264 °C (dec). IR: 2941, 2930, 2871, 2851, 2634, 2530, 2451, 2401, 1471, 1455, 1351, 1333, 1187, 1124, 1016, 992, 858, 708 cm⁻¹. ¹H NMR 1.54 (dm, J  = 13.0 Hz, 1H, 4′-H_ax), 1.62 (dquint, J  = 13.3 Hz, 1H, 9-H_syn), 1.72 [dd, J  = 11.5 Hz, J′ = 3.0 Hz, 2H, 6(8)-H_α], 1.74 (dm, J  = 13.0 Hz, 1H, 9-H_anti), 1.84-2.02 [complex signal, 9 H, 6(8)-H_β, 2(4)-H_β, 4′-H_eq, 3′(5′)-H_ax, and 3′(5′)-H_eq], 2.15 [dm, J  = 10.0 Hz, 2H, 2(4)-H_α], 2.44 [broad signal, 2H, 1(5)-H], 2.65 [tt, J  = 6.7 Hz, J′ = 1.8 Hz, 1H, 7-H], 3.05 [broad t, J  = 12.0 Hz, 2H, 2′(6′)-H_ax], 3.51 [d, J  = 12.0 Hz, 2H, 2′(6′)-H_eq]. ¹³C NMR 23.1 (CH₂, C4′), 24.6 [CH₂, C3′(5′)], 35.2 (CH₂, C9), 38.7 [CH, C1(5)], 42.0 (CH, C7), 43.7 [CH₂, C6(8)], 44.8 [CH₂, C2(4)], 51.0 [CH₂, C2′(6′)], 78.8 (C, C3). MS (EI), m/z (%): 205 (M^{• +}, 15), 163 (14), 162 ([M−C₃H₇]⁺, 100), 149 (26). Anal. Calcd for C₁₄H₂₃N·HCl (241.80): C, 69.54; H, 10.00; N, 5.79. Found: C, 69.60; H, 10.0; N, 5.78.

4.1.10. N-Methyl(tricyclo[3.3.1.0^3,7]non-3-yl)amine hydrochloride (12·HCl)

A solution of 9·HCl (275 mg, 0.99 mmol) and 5% Pd/C (50% in water, 10 mg) in absolute EtOH (25 mL) was hydrogenated at 1 atm for 24 h. The suspension was filtered, the residue was washed with EtOH, and the organic layer was concentrated in vacuo to give a solid. Crystallization from MeOH/Et₂O gave 12·HCl (165 mg, 89% yield), mp 165−166 °C. IR: 2947, 2922, 2870, 2856, 2763, 2728, 2692, 2587, 2516, 2458, 1466, 1420, 1348, 1332, 1311, 1258, 1160, 1111, 1094, 1060, 1018, 996, 630 cm⁻¹. ¹H NMR 1.61 (dquint, J  = 13.0 Hz, J′ = 2.5 Hz, 1H, 9-H_syn), 1.71 (dd, J  = 12.0 Hz, J′ = 2.5 Hz, 2H, 6(8)-H_α), 1.74 (overlapped m, 1H, 9-H_anti), 1.96–2.03 [complex signal, 6H, 6(8)-H_β, 2(4)-H_α, and 2(4)-H_β], 2.42 [complex signal, 3H, 1(5)-H, and 7-H], 2.68 (s, 3H, N-CH₃). ¹³C NMR 29.1 (CH₃, N-CH₃), 34.9 (CH₂, C9), 38.7 [CH, C1(5)], 43.1 (CH, C7), 43.8 [CH₂, C6(8)], 45.8 [CH₂, C2(4)], 71.5 (C, C3). MS (EI), m/z (%): 151 (M⁺, 15), 108 ([M−C₃H₇]⁺, 100). Anal. Calcd for C₁₀H₁₇N·HCl·0.33H₂O (193.66): C, 62.02; H, 9.71; N, 7.23. Found: C, 62.13; H, 9.63; N, 7.20.

4.1.11. [(Tricyclo[3.3.1.0^3,7]non-3-yl)methyl]amine hydrochloride (14·HCl)

To a cold (0 °C) solution of 13 (600 mg, 3.64 mmol) in anhyd THF (50 mL), LiAlH₄ (443 mg, 11.1 mmol) was added and the suspension was heated under reflux for 15 h. The suspension was cooled (ice bath), carefully basified with 10 N NaOH (10 mL), and stirred for 1 h at room temperature. The precipitate was filtered and washed with CH₂Cl₂ (3× 25 mL). The combined filtrate and washings were dried with anhyd Na₂SO₄, filtered, and excess of Et₂O·HCl was added. The solution was concentrated in vacuo to give a solid that was crystallized from MeOH/Et₂O to give 14·HCl (613 mg, 90% yield), mp >300 °C (dec). IR: 3019, 2926, 2867, 1597, 1499, 1384, 1337, 1116, 981, 864 cm⁻¹. ¹H NMR 1.61−1.72 (complex signal, 6H, 9-H_syn, 9-H_anti, 6(8)-H_α, and 2(4)-H_β], 1.75 [dd, J  = 10.5 Hz, J′ = 3.0 Hz, 2H, 2(4)-H_α], 1.81 [m, 2H, 6(8)-H_β], 2.18 [t, J  = 6.7 Hz, 1H, 7-H], 2.29 [broad signal, 2H, 1(5)-H], 3.08 (s, 2H, CH₂N). ¹³C NMR 35.8 (CH₂, C9), 38.9 [CH, C1(5)], 43.2 (CH, C7), 44.6 [CH₂, C6(8)], 47.4 [CH₂, C2(4)], 48.2 (CH₂, CH₂N), 48.8 (C, C3). MS (EI), m/z (%): 153 (24), 152 ([M+H]⁺, 36], 151 (20), 135 [(C₁₀H₁₅)⁺, 53], 134 (70), 119 (29), 96 (45), 95 (59), 94 (33), 93 (57), 92 (100), 91 (58), 79 (74), 77 (40). Anal. Calcd for C₁₀H₁₇N·HCl (187.71): C, 63.99; H, 9.66; N, 7.46; Cl, 18.89. Found: C, 64.07; H, 9.66; N, 7.43; Cl, 18.97.

4.1.12. N-Benzyl[(tricyclo[3.3.1.0^3,7]non-3-yl)methyl]amine hydrochloride (15·HCl)

From 14·HCl (500 mg, 2.67 mmol), MeOH (10 mL), NaBH₃CN (95%, 380 mg, 5.74 mmol), AcOH (0.3 mL), benzaldehyde (0.4 mL, 3.92 mmol), an additional portion of NaBH₃CN (95%, 190 mg, 2.87 mmol), and benzaldehyde (0.2 mL, 1.96 mmol) and following the procedure described for 8a, 15·HCl was obtained (567 mg, 77% yield). The analytical sample of 15·HCl was obtained by crystallization from EtOAc, mp >277 °C (dec). IR: 2931, 2865, 2781, 1588, 1446, 750, 700 cm⁻¹. ¹H NMR 1.58–1.70 [complex signal, 6H, 2(4)-H_β, 6(8)-H_α, and 9-H_syn and 9-H_anti], 1.76–1.81 [complex signal, 4H, 2(4)-H_α and 6(8)-H_β], 2.15 [t, J  = 7.0 Hz, 1H, 7-H], 2.27 [broad s, 2H, 1(5)-H], 3.11 (s, 2H, CH₂–N), 4.28 (s, 2H, CH ₂C₆H₅), 7.45–7.50 [complex signal, 3H, Ar-4-H and Ar-3(5)-H], 7.55–7.57 [m, 2H, Ar-2(6)-H]. ¹³C NMR 35.7 (CH₂, C9), 39.0 [CH, C1(5)], 44.0 (CH, C7), 44.4 [CH₂, C6(8)], 47.8 [CH₂, C2(4)], 48.4 (C, C3), 53.1 (CH₂, CH₂C₆H₅), 55.9 (CH₂, CH₂N), 130.3 [CH, Ar-C3(5)], 130.8 (CH, Ar-C4), 131.5 [CH, Ar-C2(6)], 132.0 (C, Ar-C1). MS (EI), m/z (%): 241 (M^{• +}, 6), 240 ([M−H]⁺, 8), 150 [(C₁₀H₁₆N)⁺, 10], 120 (54), 106 [(C₇H₈N)⁺, 58), 91 [(C₇H₇)⁺, 100]. Anal. Calcd for C₁₇H₂₃N·1.1HCl·0.1H₂O (283.3): C, 72.08; H, 8.65; N, 4.94; Cl, 13.77. Found: C, 72.03; H, 8.56; N, 4.85, Cl, 13.94.

4.1.13. N-Benzyl-N-methyl[(tricyclo[3.3.1.0^3,7]non-3-yl)methyl]amine hydrochloride (16·HCl)

From 15·HCl (465 mg, 1.67 mmol), acetonitrile (10 mL), formaldehyde (1.31 mL, 37% wt. in water solution, 16.7 mmol), and two portions of NaBH₃CN (95%, 314 mg, 4.75 mmol) and following the procedure described for 9, the amine 16 was obtained (411 mg, 96% yield). Its hydrochloride was obtained by adding an excess of Et₂O·HCl to a solution of the amine in EtOAc, followed by concentration in vacuo to dryness. The analytical sample of 16·HCl was obtained by crystallization from EtOAc, mp 251−252 °C. IR: 3042, 2924, 2865, 2698, 2641, 2550, 2530, 1458, 1423, 1337, 1085, 906, 745, 701 cm⁻¹. ¹H NMR 1.46 [d, J  = 9.0 Hz, 1H, 2-H_α or 4-H_α], 1.59−1.70 [complex signal, 4H, 6-H_α, 8-H_α, 9-H_syn, and 9-H_anti], 1.71−1.78 [complex signal, 3H, 4-H_α or 2-H_α, 6-H_β, and 8-H_β], 1.87 [m, 2 H, 2-H_β and 4-H_β], 2.10 [t, J  = 6.7 Hz, 1H, 7-H], 2.27 (broad s, 1H) and 2.30 (broad s, 1H) (1-H and 5-H), 2.94 (s, 3 H, CH₃–N), 3.32 (d, J  = 13.5 Hz, 1H, CH_aN), 3.46 (d, J  = 13.5 Hz, 1H, CH_bN), 4.37 (d, J  = 12.2 Hz, 1H, CH_aC₆H₅), 4.43 (d, J  = 12.2 Hz, 1H, CH_bC₆H₅), 7.50–7.52 [complex signal, 3H, Ar-4-H and Ar-3(5)-H], 7.59 [m, 2H, Ar-2(6)H]. ¹³C NMR 35.5 (CH₂, C9), 39.1 (CH) and 39.4 [CH, C1 and C5], 43.0 (CH₃, CH₃–N), 44.0 (CH₂, C6, and C8), 46.0 (CH, C7), 48.6 (C, C3), 48.8 (CH₂, C2, and C4), 62.8 (CH₂, CH₂–C₆H₅), 65.1 (CH₂, CH₂–N), 130.4 [CH, Ar-C3(5)], 130.9 (C, Ar-C1), 131.4 (CH, Ar-C4), 132.6 [CH, Ar-C2(6)]. MS (EI), m/z (%): 255 (M^{• +}, 10), 135 (17), 134 ([C₆H₅CH₂N(CH₃) CH₂]⁺, 100), 120 ([C₆H₅CH NHCH₃]⁺, 34), 91 [(C₇H₇)⁺, 89]. Anal. Calcd for C₁₈H₂₅N·HCl (291.86): C, 74.07; H, 8.98; N, 4.80; Cl, 12.15. Found: C, 74.15; H, 8.96; N, 4.81; Cl, 12.43.

4.1.14. N,N-Dimethyl[(tricyclo[3.3.1.0^3,7]non-3-yl)methyl]amine hydrochloride (17·HCl)

To a cold (0 °C) solution of 14 (128 mg, 0.68 mmol) in Et₂O (5 mL), formaldehyde (1.38 mL, 37% wt. in water solution, 17.6 mmol) and, dropwise, formic acid (1.17 mL, 30.5 mmol) were added and the mixture was stirred at 80 °C for 10 h. To the cold mixture Et₂O (15 mL) was added, 5 N NaOH (5 mL) was added dropwise and the suspension was stirred at room temperature for 15 min. The organic layer was separated and the aqueous phase was extracted with Et₂O (4× 10 mL). The combined organic phases were dried with anhyd Na₂SO₄, filtered, and an excess of Et₂O·HCl was added. Concentration in vacuo gave 17·HCl (100 mg, 68% yield). The analytical sample of 17·HCl was obtained by crystallization from MeOH/Et₂O, mp >260 °C (dec). IR (KBr): 2930, 2915, 2868, 2847, 2681, 2570, 2468, 2360, 1471, 1413, 1338, 1306, 1225, 1062, 971, 946 cm⁻¹. ¹H NMR 1.62−1.71 [complex signal, 4H, 9-H_syn, 9-H_anti, and 6(8)-H_α], 1.71−1.76 [dm, J  = 10.5 Hz, 2H, 2(4)-H_β], 1.83 [m, 2H, 6(8)-H_β], 1.87 [dd, J  = 10.5 Hz, J′ = 3.0 Hz, 2H, 2(4)-H_α], 2.19 [t, J  = 6.7 Hz, 1H, 7-H], 2.32 [broad signal, 2H, 1(5)-H], 2.95 [s, 6H, N(CH₃)₂], 3.38 (s, 2H, CH₂N). ¹³C NMR 35.7 (CH₂, C9), 39.2 [CH, C1(5)], 44.1 [CH₂, C6(8)], 45.5 (CH₃, CH₃N), 46.0 (CH, C7), 48.3 [CH₂, C2(4)], 48.6 (C, C3), 67.4 (CH₂, CH₂N). MS (EI), m/z (%): 179 (M^{• +}, 16), 91 (7), 79 (8), 77 (7), 58 ([CH₂ N(CH₃)₂]⁺, 100). Anal. Calcd for C₁₂H₂₁N·1.05HCl·0.25H₂O (222.09): C, 64.90; H, 10.23; N, 6.31; Cl, 16.76. Found: C, 64.77; H, 10.42; N, 6.32; Cl, 16.70.

4.1.15. N-[(Tricyclo[3.3.1.0^3,7]non-3-yl)methyl]guanidine hydrochloride (18·HCl)

To a cold (0 °C) solution of 14·HCl (150 mg, 0.8 mmol) in acetonitrile (2.5 mL), anhyd Et₃N (0.2 mL, 1.45 mmol), and 1H-pyrazol-1-carboxamide hydrochloride (140 mg, 0.94 mmol) were added. The suspension was heated at 70 °C for 6 h and cooled at 0 °C for 24 h. The precipitate was filtered and washed with cold acetonitrile (2× 5 mL) to give 18·HCl (129 mg, 70% yield). The above product was taken in EtOAc, excess Et₂O·HCl was added, and the solvent was eliminated in vacuo. The analytical sample of 18·HCl was obtained by crystallization from MeOH/Et₂O, mp 298−299 °C. IR (KBr): 3357, 3262, 3169, 2926, 2861, 1664, 1623, 1578, 1458, 1356, 1094, 690 cm⁻¹. ¹H NMR 1.61−1.68 [complex signal, 6H, 6(8)-H_α, 2(4)-H_β, 9-H_syn, and 9-H_anti], 1.72 [dd, J  = 10.7 Hz, J′ = 2.7 Hz, 2H, 2(4)-H_α], 1.81 [m, 2H, 6(8)-H_β], 2.12 [t, J  = 6.7 Hz, 1H, 7-H], 2.26 [broad s, 2H, 1(5)-H], 3.30 (s, 2H, CH₂N). ¹³C NMR (75.4 MHz) 36.1 (CH₂, C9), 38.8 [CH, C1(5)], 42.8 (CH, C7), 44.8 [CH₂, C6(8)], 47.7 [CH₂, C2(4)], 49.9 (CH₂, CH₂N), 50.2 (C, C3), 159.1 (C, C guanidine). MS (EI), m/z (%): 194 (12), 193 (M^{• +}, 60), 150 ([M−C₃H₇]⁺, 24), 93 (21), 92 (30), 91 (44), 79 (36), 77 (29), 72 [(C₂H₆N₃)⁺, 49], 60 ([CH₆N₃]^{• +}, 100). Anal. Calcd for C₁₁H₁₉N₃·HCl (229.75): C, 57.51; H, 8.77; N, 18.29; Cl, 15.43. Found: C, 57.65; H, 8.88; N, 18.23; Cl, 15.68.

4.1.16. N-Methyl[(tricyclo[3.3.1.0^3,7]non-3-yl)methyl]amine hydrochloride (19·HCl)

From 16·HCl (267 mg, 0.91 mmol), 5% Pd/C (50% in water, 10 mg), and absolute EtOH (30 mL) and following the procedure described for 12, 19·HCl (143 mg, 78% yield) was obtained after crystallization from MeOH/Et₂O, mp >224 °C (dec). IR: 2931, 2866, 2770, 2435, 1668, 1611, 1460, 1430, 1398, 1338, 1302, 1154, 1028, 732 cm⁻¹. ¹H NMR 1.61−1.73 [complex signal, 6H, 2(4)-H_β, 6(8)-H_α, 9-H_syn, and 9-H_anti], 1.75 [dd, J  = 10.5 Hz, J′ = 3.0 Hz, 2H, 2(4)-H_α], 1.81 [m, 2H, 6(8)-H_β], 2.19 [t, J  = 6.7 Hz, 1H, 7-H], 2.30 [broad s, 2H, 1(5)-H], 2.75 (s, 3H, CH₃N), 3.16 (s, 2H, CH₂–N). ¹³C NMR 35.0 (CH₃, CH₃N), 35.7 (CH₂, C9), 39.0 [CH, C1(5)], 43.7 (CH, C7), 44.5 [CH₂, C6(8)], 47.7 [CH₂, C2(4)], 48.5 (C, C3), 58.6 (CH₂, CH₂–N). MS (EI), m/z (%): 166 (13), 165 (M^{• +}, 100), 164 ([M−H]⁺, 48), 135 (20), 134 (87), 108 (54), 93 (46), 92 (86), 91 (55), 79 (60), 77 (39). Anal. Calcd for C₁₁H₁₉N·HCl·0.25H₂O (206.24): C, 64.06; H, 10.02; N, 6.79. Found: C, 64.02; H, 10.23; N, 6.86.

4.1.17. 3,7-Dimethyl(tricyclo[3.3.0.0^3,7]oct-1-yl)amine·HCl (21·HCl)

To a solution of acid 20 (389 mg, 2.16 mmol) in toluene (6.5 mL), Et₃N (0.4 mL, 2.9 mmol), and diphenylphosphorylazide (875 mg, 3.18 mmol) were added and the mixture was heated under reflux for 3 h. The cold (ice-bath) solution was washed with cold 1 N HCl (10× 5 mL). Then, 6 N HCl (9 mL) was added to the organic solution and the mixture was heated under reflux for 24 h. The organic layer was separated, the aqueous layer was washed with Et₂O (3× 5 mL) and the water was removed in a freeze–dryer giving 21·HCl as a white solid (296 mg, 73% yield). The analytical sample was obtained by crystallization from water, mp 210−211 °C. IR: 2959, 2945, 2891, 2863, 2765, 2685, 2579, 1602, 1493, 1480, 1460, 1308, 1285, 1163, 984 cm⁻¹. ¹H NMR 1.20 (s, 6H, C3(7)-CH₃), 1.44 [dd, J  = 8.5 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_α], 1.70−1.73 [complex signal, 4H, 2(8)-H_α, and 2(8)-H_β], 1.75 [dd, J  = 8.5 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 2.34 [t, J  = 3.0 Hz, 1H, 5-H], 4.85 (s, mobile H). ¹³C NMR 16.4 [CH₃, C3(7)-CH₃], 44.1 (CH, C5), 48.1 [C, C3(7)], 53.8 [CH₂, C4(6)], 56.7 [CH₂, C2(8)], 61.4 (C, C1). MS (EI), m/z (%): 152 ([M+H]⁺, 3), 151 (M^{• +}, 2), 138 (14), 137 (12), 124 (27), 123 (25), 111 (57), 110 (88), 109 (53), 97 (81), 96 (100), 95 (70), 94 (29), 91 ([C₇H₇ ⁺], 23), 82 (36), 81 (30), 79 (26), 77 (36), 67 (24), 55 (44), 53 (35). Anal. Calcd for C₁₀H₁₇N·HCl (187.71): C, 63.99; H, 9.67; N, 7.46; Cl, 18.89. Found: C, 63.71; H, 9.70; N, 7.48; Cl, 18.88.

4.1.18. N-Benzyl-3,7-dimethyl(tricyclo[3.3.0.0^3,7]oct-1-yl)amine hydrochloride (22a·HCl)

To a solution of 21·HCl (770 mg, 4.11 mmol) in MeOH (15 mL), NaBH₃CN (95%, 585 mg, 8.86 mmol), AcOH (0.3 mL), and benzaldehyde (653 mg, 6.16 mmol) were added, and the mixture was stirred at room temperature for 18 h. The solution was concentrated to dryness, water (30 mL) was added to the residue and the mixture was extracted with Et₂O (3× 25 mL). The combined organic extracts were washed with 2 N NaOH (3× 25 mL) and brine (2× 25 mL), dried (anhyd Na₂SO₄) and concentrated in vacuo. The residue was subjected to column chromatography (silica gel; hexane/EtOAc, 97/3) to give amine 22a (594 mg, 60% yield). An analytical sample of 22a·HCl was obtained by adding an excess of Et₂O·HCl to a solution of 22a in EtOAc and filtration of the formed precipitate, mp >258 °C (dec). IR: 2957, 2934, 2917, 2911, 2759, 2739, 2732, 2725, 2626, 2619, 2578, 2423, 1459, 1452, 1308, 1160, 1028, 731, 693 cm⁻¹. ¹H NMR 1.23 (s, 6H, C3(7)-CH₃), 1.50 [dd, J  = 9.0 Hz, J′ = 3.0 Hz, 2 H, 4(6)-H_α], 1.79 [dd, J  = 9.0 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 1.82–1.86 [complex signal, 4H, 2(8)-H_α, and 2(8)-H_β], 2.51 [t, J  = 3.0 Hz, 1H, 5-H], 4.21 (s, 2H, CH ₂C₆H₅), 4.85 (s, mobile H), 7.42−7.48 [complex signal, 3H, Ar-3(5)-H, and Ar-4-H], 7.52 [dd, J  = 8.0 Hz, J′ = 2.0 Hz, 2H, Ar-2(6)-H]. ¹³C NMR 16.4 [CH₃, C3(7)-CH₃], 43.6 (CH, C5), 47.8 [C, C3(7)], 49.6 (CH₂, CH₂–C6H₅), 53.6 [CH₂, C4(6)], 54.9 [CH₂, C2(8)], 68.2 (C, C1), 130.3 [CH, Ar-C3(5)], 130.6 (CH, Ar-C4), 130.8 (CH, Ar-C2(6)], 133.1 (C, Ar-C1). MS (EI), m/z (%): 241 (M^{• +}, 2), 227 (3), 226 (3), 213 (6), 200 (34), 199 (35), 91 ([C₆H₅CH₂]⁺, 100). Anal. Calcd for C₁₇H₂₃N·HCl (277.83): C, 73.49; H, 8.71; N, 5.04; Cl, 12.76. Found: C, 73.83; H, 8.78; N, 5.02; Cl, 12.92.

4.1.19. N-(2-Thenyl)-3,7-dimethyl(tricyclo[3.3.0.0^3,7]oct-1-yl)amine hydrochloride (22b·HCl)

From 21·HCl (187.7 mg, 1.00 mmol), NaBH₃CN (95%, 198 mg, 3 mmol), acetic acid (0.3 mL), and 2-thiophenecarbaldehyde (0.15 mL, 1.65 mmol) in methanol (10 mL) and following the above procedure, 22b·HCl (196 mg, 69% yield) was obtained. The analytical sample of 22b·HCl was obtained by crystallization from MeOH/Et₂O, mp >255 °C (dec). IR: 3062, 2952, 2919, 2887, 2727, 2689, 2549, 2451, 1583, 1477, 1440, 1375, 1307, 1280, 1247, 1159, 1068, 1007, 937, 855, 837, 731, 712, 701 cm⁻¹. ¹H NMR 1.23 (s, 6 H, C3(7)-CH₃), 1.49 [dd, J  = 8.5 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_α], 1.79 [dd, J  = 8.5 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 1.84 [complex signal, 4H, 2(8)-H_α, and 2(8)-H_β], 2.51 [t, J  = 3.0 Hz, 1H, 5-H], 4.46 (s, 2H, CH₂N), 4.86 (s, mobile H), 7.11 (dd, J  = 5.0 Hz, J′ = 4.0 Hz, 1H, Ar-4-H), 7.33 (dm, J  = 3.5 Hz, 1H, Ar-3-H), 7.56 (dd, J  = 5.0 Hz, J′ = 1.0 Hz, 1H, Ar-5-H). ¹³C NMR 16.4 [CH₃, C3(7)-CH₃], 43.5 (CH₂, CH₂N), 43.6 (CH, C5), 47.8 [C, C3(7)], 53.6 [CH₂, C4(6)], 54.9 [CH₂, C2(8)], 68.0 (C, C1), 128.7 (CH, Ar-C4), 129.2 (CH, Ar-C5), 131.4 (CH, Ar-C3), 134.0 (C, Ar-C1). MS (EI), m/z (%): 247 (M^{• +}, 2), 233 (3), 219 (7), 206 (50), 205 (30), 192 (11), 97 ([C₄H₃SCH₂]⁺, 100). Anal. Calcd for C₁₅H₂₁NS·1.1HCl·0.1H₂O (289.30): C, 62.27; H, 7.77; N, 4.84; S, 11.08; Cl, 13.48. Found: C, 62.25; H, 7.69; N, 4.85; S, 10.95; Cl, 13.07.

4.1.20. N-Benzyl-N,3,7-trimethyl(tricyclo[3.3.0.0^3,7]oct-1-yl)amine hydrochloride (23·HCl)

From a solution of 22a·HCl (635 mg, 2.29 mmol), acetonitrile (15 mL), formaldehyde (1.81 mL, 37% wt. in water solution, 23 mmol), two portions of NaBH₃CN (95%, 455 mg, 6.88 mmol) and following the procedure described for 9, the amine 23 (516 mg, 88.5% yield) was obtained. An analytical sample of 23·HCl was obtained by adding an excess of Et₂O·HCl to a solution of 23 in EtOAc followed by filtration of the obtained precipitate, mp >228 °C (dec). IR: 2952, 2886, 2680, 2439, 2372, 1456, 1310, 749, 705, 695 cm⁻¹. ¹H NMR 1.25 [s, 6H, C3(7)-CH₃], 1.56 [dd, J  = 9.0 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_α], 1.83 [dd, J  = 9.0 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 1.92–1.95 [complex signal, 4H, 2(8)-H_α, and 2(8)-H_β], 2.71 (s, 3H, CH₃N), 2.74 [t, J  = 3.0 Hz, 1H, 5-H], 4.09 (broad signal, 1H) and 4.61 (broad signal, 1H) (CH ₂C₆H₅), 4.84 (s, mobile H), 7.49−7.51 [complex signal, 3H, Ar-3(5)-H and Ar-4-H], 7.53−7.56 [m, 2H, Ar-2(6)-H]. ¹³C NMR 16.5 [CH₃, C3(7)-CH₃], 37.2 (CH₃, CH₃N), 43.3 (CH, C5), 47.6 (CH₂, CH₂C₆H₅), 53.5 [CH₂, C4(6)], 53.7 [CH₂, C2(8)], 58.7 [C, C3(7)], 76.2 (C, C1), 130.3 [CH, Ar-C3(5)], 131.1 (CH, Ar-C4), 131.2 (C, Ar-C1), 132.1 [CH, Ar-C2(6)]. MS (EI), m/z (%): 255 (M^{• +}, 3), 254 ([M−H]⁺, 3), 240 (7), 226 (7), 213 (82), 212 (28), 91 ([C₆H₅CH₂]⁺, 100). Anal. Calcd for C₁₈H₂₅N·0.95HCl (290.04): C, 74.54; H, 9.02; N, 4.83; Cl, 11.61. Found: C, 74.63; H, 9.13; N, 4.84; Cl, 11.60.

4.1.21. 1-(3,7-Dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)ethylamine hydrochloride (25·HCl)

4.1.21.1. 1-(3,7-Dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)-1-ethanone (24)

To a suspension of Li₂CO₃ (189 mg, 2.55 mmol) in H₂O (40 mL) solid 20 (900 mg, 5.00 mmol) was added and the resulting suspension was stirred for 48 h at room temperature. The water of the resulting solution was removed in a freeze–dryer giving the lithium salt of 20 as a white solid. This salt was added to anhyd Et₂O (20 mL) and the resulting suspension was cooled to 0 °C. Methyllithium (18.8 mL, 1.6 M in Et₂O, 30 mmol) was added dropwise and the suspension was heated under reflux for 18 h. To the cold (ice-bath) mixture, water (15 mL) was added dropwise, and the mixture was further stirred for 15 min. The organic layer was separated and the aqueous phase was extracted with Et₂O (3× 15 mL). The combined organic phases were dried (anhyd Na₂SO₄) and concentrated in vacuo at room temperature to give ketone 24 (382 mg, 43% yield; 57% yield based on unrecovered starting material). The aqueous layer was made acidic and extracted with CH₂Cl₂ (4× 10 mL). The combined organic phases were dried (anhyd Na₂SO₄), and concentrated in vacuo to give starting acid 20 (223 mg). IR: 2956, 2885, 1716, 1699, 1438, 1360, 1302, 1220 cm⁻¹. ¹H NMR (300 MHz) 1.18 (s, 6H, C3(7)-CH₃), 1.37 [dd, J  = 8.5 Hz, J′ = 3.6 Hz, 2H, 4(6)-H_α], 1.56−1.62 [complex signal, 4H, 2(8)-H_α and 4(6)-H_β], 1.70 [dm, J  = 7.8 Hz, 2(8)-H_β], 2.16 (d, J  = 0.6 Hz, 3H, CH₃CO), 2.60 [t, J  = 3.0 Hz, 1H, 5-H]. MS (EI), m/z (%): 178 (M^{• +}, 3), 163 ([M−CH₃]⁺, 7), 136 (11), 135 ([C₁₀H₁₅]⁺, 23), 123 (20), 122 (31), 107 (21), 95 (41), 93 (27), 43 ([CH₃CO]⁺, 100). Accurate mass measurement (ESI⁺) calcd for [C₁₂H₁₈O+H]⁺: 179.1430. Found: 179.1431.

4.1.21.2. 1-(3,7-Dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)-1-ethanone oxime

To a solution of ketone 24 (168 mg, 0.94 mmol) in ethanol (1 mL), hydroxylamine hydrochloride (103 mg, 1.49 mmol), water (0.1 mL), and powdered NaOH (190 mg, 4.75 mmol) were added and the mixture was heated under reflux for 5 min. The cold solution (ice-bath) was added to a cold solution (ice bath) of concd HCl (0.64 mmol, 7.72 mmol) and water (3.5 mL). The obtained precipitate was filtered, washed with cold water (2× 2 mL) and dried in vacuo over P₄O₁₀ to give the title oxime (135 mg, 74% yield) that was used without further purification in the next step. IR: 3234, 2949, 2881, 1667, 1446, 1371, 1018, 918, 893, 775 cm⁻¹.

4.1.21.3. 1-(3,7-Dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)ethylamine hydrochloride (25·HCl)

To a suspension of LiAlH₄ (110 mg, 2.90 mmol) in anhyd Et₂O (3 mL) a solution of the above oxime (135 mg, 0.70 mmol) in anhyd THF (2 mL) was added dropwise and the mixture was heated under reflux for 16 h. To the cold mixture, water (0.1 mL, 5.55 mmol) was added dropwise and the suspension was stirred at room temperature for 1 h. The formed precipitate was filtered through Celite^® and washed with Et₂O (3× 10 mL). The filtrate was dried (anhyd Na₂SO₄), an excess of Et₂O·HCl was added and the precipitate was filtered to give 25·HCl (66 mg, 44% global yield from 24), mp >278 °C (dec). IR: 2952, 2932, 2881, 2567, 1601, 1511, 1479, 1458, 1386, 1320, 1292, 1202, 1162, 1062 cm⁻¹. ¹H NMR 1.192 (s, 3H) and 1.195 (s, 3H) [C3-CH₃ and C7-CH₃], 1.32 [d, J  = 7.0 Hz, 3H, CH ₃CH], 1.38−1.60 (complex signal, 8H, methylene protons), 2.26 [t, J  = 3.0 Hz, 1H, 5-H], 3.54 (q, J  = 7.0 Hz, 1H, CHN), 4.86 (s, mobile H). ¹³C NMR 16.4 (CH₃, CH₃CH), 16.8 (CH₃) and 16.9 (CH₃) (C3-CH₃ and C7-CH₃), 42.1 (CH, C5), 48.4 (C) and 48.5 (C) (C3 and C7), 51.3 (CH, CHN), 54.5 (CH₂) and 54.6 (CH₂) (C4 and C6), 54.7 (C, C1), 55.2 (CH₂) and 55.4 (CH₂) (C2 and C8). MS (EI), m/z (%): 179 (M^{• +}, 2), 178 ([M−H]⁺, 3), 164 (36), 147 (50), 122 (36), 121 (77), 119 (37), 109 (45), 108 (32), 107 (100), 106 (63), 105 (73), 93 (34), 91 (76), 83 (69), 80 (30), 79 (46), 77 (36), 70 (51). Anal. Calcd for C₁₂H₂₁N·1.05HCl·0.1H₂O (219.39): C, 65.70; H, 10.22; N, 6.38; Cl, 16.97. Found: C, 65.53; H, 10.49; N, 6.36; Cl, 16.86.

4.1.22. N,N-3,7-Tetramethyl(tricyclo[3.3.0.0^3,7]oct-1-yl)amine hydrochloride (26·HCl)

From amine 21 (151 mg, 1.0 mmol) in Et₂O (5 mL), formaldehyde (1.8 mL, 37% wt. in water solution, 22.8 mmol), and formic acid (1.5 mL, 39 mmol) and following the procedure described for 17, the amine 26 was obtained as its hydrochloride. The analytical sample of 26·HCl (180 mg, 83.5% yield) was obtained by crystallization from MeOH/Et₂O, mp 173−174 °C. IR 2999, 2955, 2933, 2886, 2628, 2569, 2540, 2518, 2468, 1472, 1455, 1439, 1312, 1054 cm^–1. ¹H NMR 1.22 [s, 6 H, C3(7)-CH₃], 1.51 [dm, J  = 9.0 Hz, 2H, 4(6)-H_α], 1.75 [dd, J  = 9.0 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 1.81 [m, 4H, 2(8)-H₂], 2.59 [t, J  = 3.0 Hz, 1H, 5-H], 2.88 (s, 6H, (CH₃)₂N). ¹³C NMR 16.5 [CH₃, C3(7)-CH₃], 40.8 (CH₃, (CH₃)₂N), 42.5 (CH, C5), 47.7 [C, C3(7)], 53.2 [CH₂, C2(8)], 53.5 [CH₂, C4(6)], 75.4 (C, C1). MS (EI), m/z (%): 179 (M^{• +}, 2), 178 ([M−H]⁺, 4), 164 (14), 150 (18), 138 (22), 137 (100), 136 (79), 123 (46), 122 (45), 108 (35), 77 (24), 55 (35). Anal. Calcd for C₁₂H₂₁N·HCl (215.77): C, 66.80; H, 10.28; N, 6.49; Cl, 16.43. Found: C, 66.81; H, 10.30; N, 6.41; Cl, 16.65.

4.1.23. N,N-Dibenzyl-3,7-dimethyl(tricyclo[3.3.0.0^3,7]oct-1-yl)amine hydrochloride (27·HCl)

A mixture of 21·HCl (178 mg, 0.95 mmol), K₂CO₃ (1.03 g, 7.5 mmol), benzyl chloride (0.29 mL, 2.5 mmol) and NaI (100 mg, 0.67 mmol) in acetonitrile (10 mL) was heated under reflux for 24 h. The mixture was concentrated in vacuo and EtOAc (30 mL) was added to the residue. The organic solution was washed with water (2× 20 mL), dried (anhy Na₂SO₄) and concentrated in vacuo. The residue was subjected to column chromatography (silica gel; hexane/EtOAc, 99:1) to give amine 27 (130 mg, 41% yield). An analytical sample of 27·HCl was obtained by adding an excess of Et₂O·HCl to a solution of 27 in EtOAc and filtration of the formed precipitate, mp 191−192 °C. IR: 3034, 2959, 2920, 2887, 2864, 2806, 2674, 2590, 2546, 1526, 1482, 1457, 1420, 1400, 1312, 1162, 1014, 921, 859, 742, 692 cm⁻¹. ¹H NMR 1.25 (s, 6H, C3(7)-CH₃), 1.55 [broad d, J  = 9.0 Hz, 2H, 4(6)-H_α], 1.86 [dd, J  = 9.0 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 2.05 [s, 4H, 2(8)-H₂], 2.73 [t, J  = 3.0 Hz, 1H, 5-H], 4.38 [d, J  = 13.5 Hz, 2H) and 4.60 [d, J  = 13.5 Hz, 2H) (CH ₂C₆H₅)], 4.86 (s, mobile H), 7.23 [dm, J  = 8.0 Hz, 4H, Ar-2(6)-H], 7.34 [tm, J  = 7.5 Hz, 4H, Ar-3(5)-H], 7.39 (tt, J  = 7.5 Hz, J′ = 2.0 Hz, 2H, Ar-4-H). ¹³C NMR 16.5 [CH₃, C3(7)-CH₃], 44.2 (CH, C5), 47.3 [C, C3(7)], 53.6 [CH₂, C4(6)], 54.5 [CH₂, C2(8)], 58.4 (CH₂, CH₂C₆H₅), 78.0 (C, C1), 130.2 [CH, Ar-C3(5)], 130.9 (CH, Ar-C4), 131.9 [CH, Ar-C2(6)], 132.0 (C, Ar-C1). MS (EI), m/z (%): 331 [M^{• +}, 1], 316 (2), 289 (43), 198 ([(C₆H₅CH₂)₂NH₂]⁺, 10), 91 ([C₆H₅CH₂]⁺, 100). Anal. Calcd for C₂₄H₂₉N·1.4HCl (382.55): C, 75.34; H, 8.01; N, 3.66; Cl, 12.99. Found: C, 75.34; H, 8.10; N, 3.60; Cl, 13.09. Accurate mass measurement (ESI⁺) calcd for [C₂₄H₂₉N+H]⁺: 332.2372. Found: 332.2382.

4.1.24. N-3,7-Trimethyl(tricyclo[3.3.0.0^3,7]oct-1-yl)amine hydrochloride (28·HCl)

A mixture of 23·HCl (390 mg, 1.33 mmol) and 10% Pd/C (50% in water, 10 mg) in absolute EtOH (80 mL) was hydrogenated at 38 atm and 100 °C for 24 h. The suspension was filtered, the residue was washed with EtOH and the organic layer was concentrated in vacuo to give a solid. Crystallization from MeOH/Et₂O gave 28·HCl (240 mg, 89% yield). An analytical sample of 28·HCl was obtained by crystallization from THF, mp 167−168 °C. IR (KBr) 2961, 2939, 2807, 2739, 2521, 2431, 2392, 2370, 1458, 1310, 1161, 1099, 1077, 878 cm⁻¹. ¹H NMR 1.22 [s, 6H, C3(7)-CH₃], 1.47 [dd, J  = 8.5 Hz, J′ = 2.0 Hz, 2H, 4(6)-H_α], 1.75-1.79 [complex signal, 6 H, 4(6)-H_β, 2(8)-H_αand 2(8)-H_β], 2.47 [t, J  = 2.5 Hz, 1H, 5-H], 2.69 (s, 3H, CH₃–N), 4.85 (s, mobile H). ¹³C NMR (75.4 MHz) 16.5 [CH₃, C3(7)-CH₃], 30.1 (CH₃, CH₃–N), 43.0 (CH, C5), 47.7 [C, C3(7)], 53.6 [CH₂, C4(6)], 54.4 [CH₂, C2(8)], 68.1 (C, C1). MS (EI), m/z (%): 165 (M^{• +}, 1), 164 ([M−H]⁺, 8), 150 ([M−CH₃]⁺, 24), 136 (33), 124 (23), 123 (100), 122 (76), 109 (56), 108 (44), 94 (27). Anal. Calcd for C₁₁H₁₉N·HCl·0.15H₂O (204.44): C, 64.63; H, 10.01; N, 6.85. Found: C, 64.71; H, 9.92; N, 6.86.

4.1.25. (3,7-Dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)carboxamide (29)

A solution of acid 20 (1.12 g, 6.22 mmol) in thionyl chloride (18 mL, 0.24 mmol) was heated under reflux for 2 h. The excess thionyl chloride was removed under vacuum, the residue was taken in toluene (5 mL) and evaporated to dryness (twice). The oily yellow residue (1.16 g) was dissolved in CHCl₃, the solution was cooled to 0 °C and NH₄OH (60 mL, 25% aqueous solution) was added dropwise. After stirring for 15 h at room temperature, the suspension was extracted with CH₂Cl₂ (4× 30 mL). The aqueous layer was made acidic with concd HCl and extracted with EtOAc (3× 30 mL). The combined EtOAc extracts were dried (anhyd Na₂SO₄) and concentrated in vacuo to give the starting acid 20 (438 mg). The combined CH₂Cl₂ extracts were washed with brine (2× 30 mL), dried (anhyd Na₂SO₄), and concentrated in vacuo to give amide 29 (572 mg, 51% yield, 84% yield taking into account the recovered starting acid). An analytical sample of 29 was obtained by crystallization from EtOAc, mp 105−106 °C. IR, 3458, 3410, 3348, 3298, 3199, 3000, 2950, 2883, 1655, 1613, 1478, 1397, 1304, 1160, 790 cm⁻¹. ¹H NMR (CDCl₃) 1.17 (s, 6H, C3(7)-CH₃), 1.37 [dd, J  = 8.5 Hz, J′ = 3.5 Hz, 2H, 4(6)-H_α], 1.61 [dd, J  = 7.5 Hz, J′ = 3.5 Hz, 2H, 2(8)-H_α], 1.62 [dd, J  = 8.5 Hz, J′ = 3.5 Hz, 2H, 4(6)-H_β], 1.70 [dm, J  = 11.5 Hz, 2H, 2(8)-H_β], 2.56 [t, J  = 3.0 Hz, 1H, 5-H], 5.50 (broad signal, 1H), 5.72 (broad signal, 1H) (CONH₂). ¹³C NMR (CDCl₃) 16.3 [CH₃, C3(7)-CH₃], 43.5 (CH, C5), 47.9 [C, C3(7)], 53.5 [CH₂, C4(6)], 54.5 (C, C1), 57.1 [CH₂, C2(8)], 177.9 (C, CO). MS (EI), m/z (%): 179 (M^{• +}, 4), 164 (5), 138 (24), 135 ([C₁₀H₁₅]⁺, 21), 124 (39), 123 (42), 95 (100), 93 (38), 91 (34), 81 (72), 80 (33), 79 (60), 77 (40). Anal. Calcd for C₁₁H₁₇NO (179.26): C, 73.70; H, 9.56; N, 7.81. Found: C, 73.64; H, 9.55; N, 7.74.

4.1.26. [(3,7-Dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)methyl]amine hydrochloride (30·HCl)

To a cold (0 °C) solution of 29 (570 mg, 3.18 mmol) in anhyd THF (70 mL), LiAlH₄ (388 mg, 9.72 mmol) was added and the suspension was heated under reflux for 15 h. The suspension was cooled (ice bath), carefully basified with 10 N NaOH (5 mL) and stirred for 1 h at room temperature. The precipitate was filtered and washed with CH₂Cl₂ (3× 25 mL). The combined filtrate and washings were dried (anhyd Na₂SO₄) and excess of Et₂O·HCl was added. The solution was concentrated in vacuo to give a solid that was crystallized from MeOH/Et₂O to give 30·HCl (534 mg, 83% yield), mp >270 °C (dec). IR 2952, 2881, 1600, 1505, 1480, 1457, 1389, 1322, 1292 cm⁻¹. ¹H NMR 1.19 (s, 6 H, C3(7)-CH₃), 1.39 [dd, J  = 8.0 Hz, J′ = 4.0 Hz, 2 H, 4(6)-H_α], 1.43 [dd, J  = 8.0 Hz, J′ = 4.0 Hz, 2H, 2(8)-H_α], 1.49 [dm, J  = 7.5 Hz, 2H, 2(8)-H_β], 1.62 [dd, J  = 8.0 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 2.20 [t, J  = 3.0 Hz, 1H, 5-H], 3.19 (s, 2 H, CH₂N), 4.85 (s, mobile H). ¹³C NMR (75.4 MHz) 16.8 [CH₃, C3(7)-CH₃], 42.8 (CH, C5), 43.8 (CH₂, CH₂N), 48.6 [C, C3(7)], 49.7 (C, C1), 54.6 [CH₂, C4(6)], 56.7 [CH₂, C2(8)]. MS (EI), m/z (%): 166 (1), 165 (M^{• +}, 1), 152 (3), 151 (3), 148 (8), 136 (26), 135 ([C₁₀H₁₅]⁺, 46), 133 (30), 107 (82), 106 (41), 105 (43), 93 (100), 92 (38), 91 (91), 79 (49), 77 (51), 71 (41). Anal. Calcd for C₁₁H₁₉N·HCl·0.5H₂O (210.75): C, 62.69; H, 10.04; N, 6.65; Cl, 16.82. Found: C, 62.38; H, 9.71; N, 6.58, Cl, 16.55.

4.1.27. N-Benzyl[(3,7-dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)methyl]amine hydrochloride (31·HCl)

From 30·HCl·0.5H₂O (500 mg, 2.37 mmol), MeOH (10 mL), NaBH₃CN (95%, 335 mg, 5.3 mmol), AcOH (0.3 mL), and benzaldehyde (395 mg, 3.68 mmol) and following the procedure described for 22a, 31·HCl (489 mg, 68% yield) was obtained, mp >270 °C (dec). IR: 2948, 2880, 2781, 2371, 1586, 1478, 1447, 1420, 1382, 1355, 1321, 1289, 1237, 1084, 1025, 748, 698 cm⁻¹. ¹H NMR 1.18 (s, 6H, 3(7)-CH₃), 1.37 [dd, J  = 8.5 Hz, J′ = 3.5 Hz, 2H, 4(6)-H_α], 1.44 [dd, J  = 8.0 Hz, J′ = 3.5 Hz, 2H, 2(8)-H_α], 1.49 [dm, J  = 8.0 Hz, 2H, 2(8)-H_β], 1.61 [dd, J  = 8.5 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 2.18 [t, J  = 3.0 Hz, 1H, 5-H], 3.25 (s, 2H, CH₂N), 4.26 (s, 2H, CH ₂C₆H₅), 4.86 (s, mobile H), 7.46–7.50 [complex signal, 3H, Ar-3(5)-H and Ar-4-H], 7.55 [m, 2H, Ar-2(6)-H]. ¹³C NMR 16.7 [CH₃, C3(7)-CH₃], 43.5 (CH, C5), 48.6 [C, C3(7)], 48.9 (C, C1), 51.4 (CH₂, CH₂N), 53.1 (CH₂, C₆H₅ CH₂), 54.6 [CH₂, C4(6)], 57.1 [CH₂, C2(8)], 130.3 [CH, Ar-C3(5)], 130.8 (CH, Ar-C4), 131.4 [CH, Ar-C2(6)], 132.1 (C, Ar-C1). MS (EI), m/z (%): 255 (M^{• +}, 3), 254 ([M−H]⁺, 2), 199 (10), 120 ([C₆H₅CH₂ ⁺NH CH₂], 67), 93 (18), 91 ([C₆H₅CH₂]⁺, 100). Anal. Calcd for C₁₈H₂₅N·HCl·0.05 H₂O (292.76): C, 73.85; H, 8.99; N, 4.78; Cl, 12.11. Found: C, 73.58; H, 8.91; N, 4.70; Cl, 12.47.

4.1.28. N-Benzyl-N-methyl[(3,7-dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)methyl]amine hydrochloride (32·HCl)

From a solution of 31·HCl (400 mg, 1.37 mmol), acetonitrile (10 mL), formaldehyde (1.08 mL, 37% wt. in water solution, 13.7 mmol) and two portions of NaBH₃CN (95%, 272 mg, 4.11 mmol) and following the procedure described for 9, the amine 32 (260 mg, 70.5% yield) was obtained. Its hydrochloride was obtained by adding an excess of Et₂O·HCl to a solution of the amine in EtOAc followed by concentration to dryness in vacuo. The analytical sample of 32·HCl was obtained by crystallization from EtOAc, mp 215−216 °C. IR: 3030, 3011, 2946, 2879, 2862, 2695, 2635, 2512, 1478, 1455, 1070, 917, 906, 746, 697 cm⁻¹. ¹H NMR 1.18 [s, 6H, C3(7)-CH₃], 1.40 [dd, J  = 8.5 Hz, J′ = 3.5 Hz, 2H, 4(6)-H_α], 1.45-1.60 [complex signal, 4H, 2(8)-H_α, and 2(8)-H_β], 1.62 [dd, J  = 8.5 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 2.16 [t, J  = 3.0 Hz, 1H, 5-H], 2.89 (s, 3H, CH₃N), 3.43 (d, J  = 13.5 Hz, 1H) and 3.54 (d, J  = 13.5 Hz, 1H) (CH₂N), 4.33 (d, J  = 12.5 Hz, 1H) and 4.43 (d, J  = 12.5 Hz, 1H) (CH ₂C₆H₅), 7.49–7.52 [complex signal, 3H, Ar-3(5)-H and Ar-4-H], 7.57 [m, 2H, Ar-2(6)-H]. ¹³C NMR 16.6 [CH₃, C3(7)-CH₃], 42.4 (CH₃, CH₃–N), 44.8 (CH, C5), 48.5 [C, C3(7)], 48.7 (C, C1), 54.4 [CH₂, C4(6)], 57.8 [CH₂, C2(8)], 60.3 (CH₂, CH₂N), 62.3 (CH₂, CH₂C₆H₅), 130.4 [CH, Ar-C3(5)], 130.8 (C, Ar-C1), 131.3 (CH, Ar-C4), 132.5 [CH, Ar-C2(6)]. MS (EI), m/z (%): 269 (M^{• +}, 7), 213 (15), 134 (87), 120 (13), 107 (10), 93 (15), 92 (13), 91 ([C₆H₅CH₂]⁺, 100). Anal. Calcd for C₁₉H₂₇N·HCl (305.89): C, 74.60; H, 9.23; N, 4.58; Cl, 11.59. Found: C, 74.51; H, 9.26; N, 4.55; Cl, 11.74.

4.1.29. N,N-Dimethyl[(3,7-dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)methyl]amine hydrochloride (33·HCl)

From a cold (0 °C) solution of 30·HCl (80 mg, 0.48 mmol) in Et₂O (5 mL), formaldehyde (1.0 mL, 37% wt. in water solution, 12.7 mmol) and formic acid (0.85 mL, 22 mmol) and following the procedure described for 17, 33·HCl was obtained. The analytical sample of 33·HCl (68 mg, 61% yield) was obtained by crystallization from THF, mp >250 °C. IR (KBr): 2952, 2884, 2691, 1479, 1412, 1316, 1211, 1136, 973, 948 cm⁻¹. ¹H NMR 1.20 [s, 6H, C3(7)-CH₃], 1.43 [dd, J  = 8.5 Hz, J′ = 3.5 Hz, 2H, 4(6)-H_α], 1.52 [dd, J  = 7.5 Hz, J′ = 3.5 Hz, 2H, 2(8)-H_α], 1.57 [dm, J  = 7.5 Hz, 2H, 2(8)-H_β], 1.65 [dd, J  = 8.5 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 2.25 [t, J  = 3.0 Hz, 1H, 5-H], 2.93 (s, 6H, (CH₃)₂N), 3.47 (s, 2H, CH₂N), 4.85 (s, mobile H). ¹³C NMR 16.6 [CH₃, C3(7)-CH₃], 44.7 (CH, C5), 45.1 (CH₃, CH₃N), 48.5 [C, C3(7)], 54.5 [CH₂, C4(6)], 57.7 [CH₂, C2(8)], 62.5 (CH₂, CH₂N). The signal corresponding to C1 was not observed. MS (EI), m/z (%): 193 (M^{• +}, 3), 137 (5), 107 (7), 93 (12), 91 (11), 58 ([Me₂NCH₂]⁺, 100). Anal. Calcd for C₁₃H₂₃N·1.6HCl (251.67): C, 62.04; H, 9.85; N, 5.57. Found: C, 62.23; H, 10.16; N, 5.76. Accurate mass measurement (ESI⁺) calcd for [C₁₃H₂₃N+H]⁺: 194.1903. Found: 194.1909.

4.1.30. N-[(3,7-Dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)methyl]piperidine hydrochloride (34·HCl)

From 30·HCl (201 mg, 1.00 mmol), DMF (2.5 mL), anhyd Et₃N (0.4 mL, 2.9 mmol), 1,5-dibromopentane (0.17 mL, 1.2 mmol) and following the procedure described for 11, 34·HCl (111 mg, 41% yield) was obtained. The analytical sample of 34·HCl was obtained by crystallization from 2-propanol, mp >265 °C (dec). IR: 2948, 2879, 2857, 2644, 2580, 2534, 1477, 1455, 1438, 1376, 1318, 950 cm⁻¹. ¹H NMR 1.20 [s, 6H, C3(7)-CH₃], 1.43 [dd, J  = 8.5 Hz, J′ = 3.5 Hz, 2H, 4(6)-H_α], 1.52 [dd, J  = 7.5 Hz, J′ = 3.5 Hz, 3 H, 2(8)-H_α], 1.50–1.55 (overlapped m, 1H, 4′-H_ax], 1.57 [dm, J  = 7.5 Hz, 2H, 2(8)-H_β], 1.65 [dd, J  = 9.0 Hz, J′ = 3.0 Hz, 2 H, 4(6)-H_β], 1.75–1.97 [broad signal, 5 H, 4′-H_eq, 3′(5′)-H_ax, and 3′(5′)-H_eq], 2.24 [t, J  = 2.5 Hz, 1H, 5-H], 3.02 [broad signal, 2 H, 2′(6′)-H_ax], 3.42 (s, 2 H, CH₂N), 3.53 [broad signal, 2 H, 2′(6′)-H_eq], 4.85 (s, mobile H). ¹³C NMR 16.6 [CH₃, C3(7)-CH₃], 22.5 (CH₂, C4′), 23.8 [CH₂, C3′(5′)], 45.1 (CH, C5), 48.4 [C, C3(7)], 49.4 (C, C1), 54.5 [CH₂, C4(6)], 55.3 [CH₂, C2′(6′)], 58.1 [CH₂, C2(8)], 61.5 (CH₂, CH₂N). MS (EI), m/z (%):233 (M^{• +}, 9), 177 (14), 98 ([C₅H₁₀NCH₂]⁺, 100), 93 (13), 91 (13), 84 ([C₅H₁₀N]⁺, 17). Anal. Calcd for C₁₆H₂₇N·HCl (269.86): C, 71.21; H, 10.46; N, 5.19; Cl, 13.14. Found: C, 71.19; H, 10.45; N, 5.17; Cl, 13.12.

4.1.31. N-[(3,7-dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)methyl]guanidine hydrochloride (35·HCl)

From a solution of 30·HCl (150 mg, 0.74 mmol), acetonitrile (2.5 mL), anhyd Et₃N (0.2 mL, 1.45 mmol) and 1H-pyrazol-1-carboxamidine hydrochloride (130 mg, 0.89 mmol) and following the procedure described for 18, 35·HCl (139 mg, 77% yield) was obtained. The analytical sample of 35·HCl was obtained by crystallization from MeOH/Et₂O, mp 214−215 °C. IR: 3600–3000 (max at 3376, 3247, 3170), 2948, 2879, 1646, 1456, 1354, 1319, 1291, 1160 cm⁻¹. ¹H NMR 1.18 [s, 6H, C3(7)-CH₃], 1.37 [dd, J  = 7.5 Hz, J′ = 3.5 Hz, 2H, 4(6)-H_α], 1.39-1.46 [complex signal, 4H, 2(8)-H_α and 2(8)-H_β], 1.61 [dd, J  = 7.5 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 2.12 [t, J  = 2.5 Hz, 1H, 5-H], 3.41 (s, 2H, CH₂N), 4.86 (s, mobile H). ¹³C NMR 16.9 [CH₃, C3(7)-CH₃], 42.7 (CH, C5), 45.6 (CH₂, CH₂N), 48.5 [C, C3(7)], 51.5 (C, C1), 54.8 [CH₂, C4(6)], 56.9 [CH₂, C2(8)], 158.9 (C, C guanidine). MS (EI), m/z (%): 209 (9), 208 ([M+H]⁺, 9), 195 (5), 194 (5), 167 (14), 166 (15), 154 (12), 153 (12), 148 (17), 133 (31), 119 (22), 107 (81), 106 (42), 105 (48), 93 (83), 92 (38), 91 (100), 79 (46), 77 (66), 75 (39), 74 (38), 63 (47), 62 (68), 61 (48). Anal. Calcd for C₁₂H₂₁N₃·HCl·1.5H₂O (270.80): C, 53.22; H, 9.30; N, 15.52. Found: C, 53.37; H, 9.03; N, 15.52.

4.1.32. N-Methyl[(3,7-dimethyltricyclo[3.3.0.0^3,7]oct-1-yl)methyl]amine hydrochloride (36·HCl)

From 32·HCl (200 mg, 0.65 mmol), 10% Pd/C (50% in water, 10 mg) and absolute ethanol (25 mL) and following the procedure described for 28, 36·HCl (120 mg, 85% yield) was obtained after crystallization from MeOH/Et₂O, mp >255 °C. IR: 2952, 2880, 2764, 1588, 1458, 1427, 1385, 1325, 1292, 1088, 1022, 806 cm⁻¹. ¹H NMR 1.19 [s, 6H, C3(7)-CH₃], 1.40 [dd, J  = 8.5 Hz, J′ = 3.5 Hz, 2H, 4(6)-H_α], 1.43-1.46 [dd, J  = 7.5 Hz, J′ = 3.5 Hz, 2H, 2(8)-H_α], 1.50 [dm, J  = 7.5 Hz, 2H, 2(8)-H_β], 1.61 [dd, J  = 8.5 Hz, J′ = 3.0 Hz, 2H, 4(6)-H_β], 2.22 [t, J  = 3.0 Hz, 1H, 5-H], 2.74 (s, 3H, CH₃N), 3.27 (s, 2H, CH₂N), 4.86 (s, mobile H). ¹³C NMR 16.7 [CH₃, C3(7)-CH₃], 34.8 (CH₃, CH₃N), 43.2 (CH, C5), 48.6 [C, C3(7)], 54.0 (CH₂, CH₂N), 54.6 [CH₂, C4(6)], 57.0 [CH₂, C2(8)]. The signal corresponding to C1 was not observed. MS (EI), m/z (%): 179 (M^{• +}, 4), 165 (5), 164 (4), 148 (6), 147 (6), 136 (15), 135 ([C₁₀H₁₅]⁺, 34), 134 (32), 133 (27), 124 (26), 123 (29), 107 (71), 106 (35), 105 (44), 93 (100), 92 (38), 91 (97), 79 (42), 77 (56). Anal. Calcd for C₁₂H₂₁N·HCl·0.5H₂O (224.77): C, 64.12; H, 10.31; N, 6.23. Found: C, 64.22; H, 10.24; N, 6.35.

4.2. Trypanosoma brucei culturing and drug test

Cultures of bloodstream form T. brucei (strain 427) were maintained at 37 °C in modified Iscove’s medium (pH 7.4).²⁰ Trypanocidal activity was assessed by growing parasites for 48 h in the presence of various drug concentrations and determining the levels which inhibited growth by 50% (IC₅₀) and 90% (IC₉₀). In the case of untreated cultures (volume 4 mL), cell densities increased from 0.25 × 10⁵ to 1 × 10⁶ cells mL⁻¹ over this period. Experiments were performed in triplicate. Cell densities at each drug concentration were determined using a hemocytometer (Weber Scientific International Ltd), and drug sensitivity was expressed as a percentage of growth of control cells.

4.3. NMDA receptor antagonist activity

The functional assay of antagonist activity at NMDA receptors was performed using primary cultures of cerebellar granule neurons, which were prepared according to established protocols.¹⁸ Cells were grown on 10 mm poly-l-lysine coated glass cover slips, and used for the experiments after 7–14 days in vitro. Cells were loaded with 6 μM Fura-2 AM (Invitrogen-Molecular Probes) for 45 min. Afterwards, the coverslip was mounted on a quartz cuvette containing a Locke–Hepes buffer using a special holder. Measurements were performed using a PerkinElmer LS-50B fluorometer equipped with a fast-filter accessory, under mild agitation and at 37 °C. Analysis from each sample was recorded real-time during 1200 s. After stimulation with NMDA or glutamate (100 μM, in the presence of 10 μM glycine), increasing cumulative concentrations of the compound to be tested were added. The percentages of inhibition at every tested concentration were analyzed using a non-linear regression curve fitting (variable slope) by using the software GraphPad Prism 4.0.

4.4. Antiviral evaluation

The antiviral activity of the compounds was determined in established cell culture assays using a selection of DNA and RNA viruses, including three subtypes of influenza virus [A/Puerto Rico/8/34 (H1N1); A/Hong Kong/7/87 (H3N2) and B/Hong Kong/5/72].²¹ The compounds’ inhibitory effect on virus replication as well as their cytotoxicity were monitored by microscopical examination, and confirmed by the colorimetric MTS cell viability assay.

4.5. Dopaminergic evaluation

4.5.1. Synaptosomal preparation

Female Wistar rats (200–250 g) were used throughout. Briefly, rats were killed by decapitation and the striatum was dissected and homogenized in 10 volumes (w/v) of 0.32 M sucrose using a Potter–Elvejhem. The resulting crude synaptosomal preparation was centrifuged at 1000g for 10 min. The supernatant was stored and the pellet was resuspended in 10 volumes of 0.32 M sucrose and recentrifuged. The two supernatants were combined and the mixture centrifuged at 16,000g for 30 min. The resultant pellet was suspended in 10 volumes of ice-cold Krebs medium. Protein concentrations were determined using the Bradford protein assay.

4.5.2. [³H]DA uptake assay

[³H]Dopamine uptake was evaluated on aliquots of the synaptosomal preparation. After a 10 min preincubation at 37 °C in Krebs buffer containing 10 μM pargyline (to block metabolism of dopamine by monoamine oxidase), [³H]dopamine (47 Ci/mmole, Amersham) was added to a final 0.5 nM concentration. Ten minute incubations were stopped by dilution into ice-cold Krebs medium. Samples were filtered rapidly through Grade 30 fiberglass filters (Schleicher & Schuell) using a Brandel cell harvester (model M-24, Biochemical Research and Development Laboratories, Inc.). Filters were washed twice with 3 mL cold Krebs medium and dried. Non-specific [³H]DA uptake was determined in duplicate samples in the presence of 10 μM nomifensine (dopamine uptake inhibitor). Filters were placed into scintillation mixture (Optiphase ‘Hisafe’ 2, Perkin-Elmer) and radioactivity was determined by scintillation spectrometry.