IMDAV reaction between phenyl­maleic anhydride and thien­yl(fur­yl)allyl­amines: synthesis and mol­ecular structure of (3aSR,4RS,4aRS,7aSR)-5-oxothieno- and (3aSR,4SR,4aRS,7aSR)-5-oxofuro[2,3-f]iso­indole-4-carb­oxy­lic acids

To establish the scope and limitations of the IMDAV reaction by elucidation of its regio- and stereoselectivity, the products of the reaction between phenyl­maleic anhydride and thien­yl(fur­yl)allyl­amines were studied by X-ray diffraction

Abstract

The title compounds C₂₄H₂₁NO₃S, I, and C₂₄H₂₁NO₄, II, are the products of the IMDAV reaction between phenyl­maleic anhydride and thien­yl(fur­yl)allyl­amines. Their mol­ecular structures comprise fused tricyclic systems containing thio­phene, cyclo­hexene and pyrrolidine rings (I) or furan, cyclo­hexene and pyrrolidine rings (II). The central cyclo­hexene and pyrrolidine rings in both compounds adopt slightly twisted boat and envelope conformations, respectively. The dihedral angles between the basal plane of the pyrrolidine ring and the thio­phene (in I) or furan (in II) ring plane are 22.74 (16) and 26.29 (5)°, respectively. The nitro­gen atom both in I and II has practically planar environment [the sums of the bond angles are 359.8 and 358.9°, respectively]. In the crystal of I, the mol­ecules form hydrogen-bonded zigzag chains along [010] through strong inter­molecular O—H⋯O hydrogen bonds involving carb­oxy­lic and keto groups, whereas in the crystal of II, the mol­ecules are joined into centrosymmetric dimers by strong O—H⋯O hydrogen bonds between the carb­oxy­lic groups. In II, the atoms involved into these hydrogen bonds (and hence the whole carb­oxy­lic group) are disordered over two sets of sites with an occupancy ratio of 0.6:0.4. Compounds I and II crystallize as racemates consisting of enanti­omeric pairs of the 3aSR,4RS,4aRS,7aSR and 3aSR,4SR,4aRS,7aSR diastereomers, respectively.

Chemical context  

Cascade transformations including one or more tandem or sequential [4 + 2] cyclo­addition reactions are a useful and high-usage tool in organic synthesis (Parvatkar et al., 2014 ▸; Sears & Boger, 2016 ▸; Borisova et al., 2018 ▸). In most cases, conjugated linear or cyclic alkadienes are the starting mat­erials for these transformations. Along with this, it has long been known that furan, thio­phene and pyrrole, possessing a conjugated system of double bonds, can also act as a diene moiety. Around 50 years ago, it was found that 2-vinyl­furans and 2-vinyl­thio­phenes can play the role of dienes in the inter­molecular Diels–Alder reaction, which cleared a short way to benzo­furan or benzo­thio­phene derivatives (Paul, 1943 ▸; Szmuszkovicz & Modest, 1950 ▸; Schmidt, 1953 ▸; Scully & Brown, 1953 ▸; Davies & Porter, 1957a ▸,b ▸; Kaufmann & Sen Gupta, 1963 ▸; Ancerewicz & Vogel, 1993 ▸; Drew et al., 2002 ▸; Wavrin et al., 2004 ▸; Ghobsi et al., 2008 ▸). At the end of the last century, it was demonstrated that this reaction could be performed in an intra­molecular variant when both a heterocyclic diene and a dienophilic moiety are incorporated in the same mol­ecule.

The IMDAV (IntraMolecular Diels–Alder Vinylarenes) reaction (Fig. 1 ▸) has become a powerful tool in organic synthesis because of its simplicity and reliability, which assures good yields of benzo­furans and benzo­thio­phenes annulated with other carbo- and heterocycles (Maas et al., 2006 ▸; Patre et al., 2007 ▸; Kim et al., 2014 ▸).

Figure 1.

Intra- and inter­molecular Diels–Alder reaction in vinyl­furans and vinyl­thio­phenes in the synthesis of benzo­furans and benzo­thio­phenes.

Previously, with the example of the inter­action between maleic anhydride and 3-thien­yl(fur­yl)allyl­amines, our group demonstrated the possibility of the domino-sequence involving N-acyl­ation, IMDAV reaction and aromatization steps leading to 4H-furo- or thieno[2,3-f]iso­indoles (Horak et al., 2015 ▸, 2017 ▸; Zubkov et al., 2016 ▸). The aim of the present study was elucidation of the regio- and stereoselectivity of the reaction between phenyl­maleic anhydride and thien­yl(fur­yl)allyl­amines in order to establish the scope and the limitations of the IMDAV reaction (Fig. 2 ▸).

Figure 2.

Synthesis of (3aSR,4RS,4aRS,7aSR)-5-oxothieno[2,3-f]iso­indole-4-carb­oxy­lic acid (I) and (3aSR,4SR,4aRS,7aSR)-5-oxofuro[2,3-f]iso­indole-4-carb­oxy­lic acid (II).

The reaction proceeds smoothly at room temperature, a simple filtration of the resulting crystalline products from ethyl acetate giving adducts I and II in good yields. The Diels–Alder reaction proceeds regio- and stereoselectively as an exo-[4 + 2] cyclo­addition (Fig. 2 ▸). The nucleophilic attack of the nitro­gen atom is directed at the least sterically hindered carbon atom of the carbonyl group of phenyl­maleic anhydride, thus amide A is not formed. The inter­mediate amide B cannot be isolated, and the spontaneous intra­molecular Diels–Alder reaction completes the process, leading to the target compounds I and II. The migration of proton H3a in adducts I, II and the formation of compound C is not observed under these conditions (Horak et al., 2015 ▸, 2017 ▸; Zubkov et al., 2016 ▸).

Structural commentary  

Despite the very similar mol­ecular structures, compounds I, C₂₄H₂₁NO₃S and II, C₂₄H₂₁NO₄ are not isostructural. Compound I crystallizes in the monoclinic space group P2₁/n, while compound II crystallizes in the triclinic space group P .

The mol­ecules of I and II comprise fused tricyclic systems containing thio­phene, cyclo­hexene and pyrrolidine rings in I (Fig. 3 ▸) and furan, cyclo­hexene and pyrrolidine rings in II (Fig. 4 ▸). The central cyclo­hexene and pyrrolidine rings in both compounds adopt slightly distorted boat and envelope conformations, respectively. The dihedral angles between the basal plane of the pyrrolidine ring (N5/N6/C4A/C7) and the thio­phene (in I) or furan (in II) ring planes are 22.74 (16) and 26.29 (5)°, respectively. The N6 nitro­gen atom both in I and II has practically planar environment (the sums of the bond angles are 359.8 and 358.9°, respectively).

Figure 3.

Mol­ecular structure of I. Displacement ellipsoids are shown at the 50% probability level. H atoms are presented as small spheres of arbitrary radius.

Figure 4.

Mol­ecular structure of II. Displacement ellipsoids are shown at the 50% probability level. H atoms are presented as small spheres of arbitrary radius. The minor occupancy position of the –COOH group is depicted with dashed lines.

In the mol­ecule of II, the carb­oxy­lic group is disordered over two orientations with inter­changing hydrogen atom positions (Fig. 4 ▸), the occupancy ratio being 0.6:0.4.

The mol­ecules of I and II possess four asymmetric centers at the C3A, C4, C4A and C7A carbon atoms and potentially can have numerous diastereomers. The crystals of I and II are racemic and consist of enanti­omeric pairs with the following relative configuration of the centers: 3aSR,4RS,4aRS,7aSR and 3aSR,4SR,4aRS,7aSR, respectively, thus I and II differ in the configuration at the C4 atom.

Supra­molecular features  

In the crystal of I, mol­ecules form hydrogen-bonded zigzag chains propagating along [010] through strong O—H⋯O hydrogen bonds involving the carb­oxy­lic and keto groups (Table 1 ▸, Fig. 5 ▸).

Table 1. Hydrogen-bond geometry (Å, °) for I .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O3i	1.04 (5)	1.63 (5)	2.667 (4)	174 (4)

Symmetry code: (i) .

Figure 5.

The hydrogen-bonded zigzag chains along the b-axis direction in I. Dashed lines indicate the inter­molecular O—H⋯O hydrogen bonds.

Contrary to I, in the crystal of II, mol­ecules form hydrogen-bonded centrosymmetric dimers through pairs of strong O—H⋯O hydrogen bonds between two carb­oxy­lic groups (Table 2 ▸, Fig. 6 ▸). The dimers are stacked along the a-axis direction.

Table 2. Hydrogen-bond geometry (Å, °) for II .

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3B⋯O2i	0.91 (3)	1.79 (3)	2.692 (3)	176 (3)
O3′—H3C⋯O2′i	0.91 (5)	1.79 (5)	2.690 (6)	169 (4)

Symmetry code: (i) .

Figure 6.

The hydrogen-bonded centrosymmetric dimers of II. Dashed lines indicate the inter­molecular O—H⋯O hydrogen bonds. The minor occupancy –COOH groups are omitted for clarity.

Synthesis and crystallization  

2-Methyl-4,6-diphenyl-4,4a,5,6,7,7a-hexa­hydro-3aH-thieno(furo)[2,3-f]iso­indole-4-carb­oxy­lic acids (I and II) were synthesized using a method similar to the procedure described recently (Horak et al., 2015 ▸, 2017 ▸; Zubkov et al., 2016 ▸).

General procedure. A solution of N-[(2E)-3-(5-methyl­thio­phen-2-yl)prop-2-en-1-yl]aniline (for I) or N-[(2E)-3-(5-methyl­furan-2-yl)prop-2-en-1-yl]aniline (for II) (2 mmol) in ethyl acetate (10 mL) was placed into a 25 mL round-bottom flask and then phenyl­maleic anhydride (0.35 g, 2.0 mmol) was added. The mixture was stirred for two days at room temperature. The formed precipitate was filtered off, washed with Et₂O (2 × 10 mL) and dried in air. The resulting product was recrystallized from a mixture of EtOH–DMF (5:1 v:v) to afford the analytically pure samples of target products.

(3a RS ,4 SR ,4a SR ,7a SR )-2-Methyl-5-oxo-4,6-diphenyl-4,4a,5,6,7,7a-hexa­hydro-3a H -thieno[2,3- f ]iso­indole-4-carb­oxy­lic acid (I). Colourless prisms. Yield 0.69 g (85%). M.p. = 447.1–448.1 K. IR (KBr), ν (cm⁻¹): 3095, 1701. ¹H NMR (DMSO-d ₆, 600.2 MHz, 301 K) δ = 13.04 (s, 1H, CO₂H), 7.52–7.03 (m, 10H, HAr), 6.30 (dt, 1H, H8, J = 1.0, J = 3.5), 5.15 (pent, 1H, H3, J = 1.3), 4.16–4.14 (m, 1H, H3a), 3.99 (dd, 1H, H7a, J = 7.6, J = 8.8), 3.67 (dd, 1H, H7b, J = 8.8, J = 10.8), 2.95–2.89 (m, 1H, H7a), 2.25 (d, 1H, H4a, J = 12.6), 1.92 (q, 3H, CH₃, J = 1.3). ¹³C NMR (DMSO-d ₆, 150.9 MHz, 301 K): δ = 175.4, 171.2 (CO₂, NCO), 143.1, 141.3, 140.4, 136.6, 129.1 (2C), 129.0 (2C), 127.7 (2C), 126.5, 124.1, 120.5, 120.3, 119.7 (2C), 61.9, 60.1, 54.7, 49.5, 37.9, 16.7 (CH₃). MS (APCI): m/z = 404 [M + H]⁺.

(3a RS ,4 RS ,4a SR ,7a RS )-2-Methyl-5-oxo-4,6-diphenyl-4,4a,5,6,7,7a-hexa­hydro-3a H -furo[2,3- f ]iso­indole-4-carb­oxy­lic acid (II). Colourless prisms. Yield 0.60 g (77%). M.p. = 422-423 K. IR (KBr), ν (cm⁻¹): 1703, 1656. ¹H NMR (DMSO-d ₆, 600.2 MHz, 301 K) δ = 13.00 (s, 1H, CO₂H), 7.55 (dd, 2H, HAr, J = 7.6, J = 8.3), 7.33 (dd, 2H, HAr, J = 7.6, J = 8.6), 7.24 (dd, 2H, HAr, J = 7.6, J = 8.3), 7.15–7.13 (m, 3H, HAr), 7.08 (t, 1H, HAr, J = 7.6), 5.59 (dt, 1H, H8, J = 1.0, J = 3.5), 4.68 (dd, 1H, H3a, J = 1.0, J = 1.5), 4.08–4.02 (m, 2H, H3, H7a), 3.68 (dd, 1H, H7b, J = 8.8, J = 10.8), 2.94–2.88 (m, 1H, H7a), 2.40 (d, 1H, H4a, J = 12.1), 1.91 (s, 3H, CH₃). ¹³C NMR (DMSO-d ₆, 150.9 MHz, 301 K): δ = 174.8, 170.7 (CO₂, NCO), 157.8, 154.3, 141.9, 139.9, 128.8 (2C), 128.5 (2C), 127.1 (2C), 125.9, 123.5, 119.1 (2C), 100.2, 97.6, 60.9, 53.4, 52.5, 49.3, 35.1, 13.3 (CH₃). MS (APCI): m/z = 388 [M + H]⁺.

Refinement  

Crystal data, data collection and structure refinement details are summarized in Table 3 ▸. X-ray diffraction studies were carried out on the ‘Belok’ beamline of the National Research Center ‘Kurchatov Institute’ (Moscow, Russian Federation) using a Rayonix SX165 CCD detector. A total of 720 images for each compounds were collected using an oscillation range of 1.0° (φ scan mode, two different crystal orientations) and corrected for absorption using the SCALA program (Evans, 2006 ▸). The data were indexed, integrated and scaled using the utility iMOSFLM in the CCP4 program (Battye et al., 2011 ▸).

Table 3. Experimental details.

	I	II
Crystal data
Chemical formula	C24H21NO3S	C24H21NO4
M r	403.48	387.42
Crystal system, space group	Monoclinic, P21/n	Triclinic, P
Temperature (K)	100	100
a, b, c (Å)	14.572 (3), 8.7989 (18), 16.982 (3)	8.1851 (16), 11.025 (2), 11.795 (2)
α, β, γ (°)	90, 111.92 (3), 90	99.14 (3), 92.51 (3), 107.99 (3)
V (Å3)	2020.0 (8)	994.6 (4)
Z	4	2
Radiation type	Synchrotron, λ = 0.96260 Å	Synchrotron, λ = 0.81182 Å
μ (mm−1)	0.41	0.12
Crystal size (mm)	0.15 × 0.10 × 0.10	0.20 × 0.12 × 0.08
Data collection
Diffractometer	Rayonix SX165 CCD	Rayonix SX165 CCD
Absorption correction	Multi-scan (SCALA; Evans, 2006 ▸)	Multi-scan (SCALA; Evans, 2006 ▸)
T min, T max	0.930, 0.950	0.963, 0.987
No. of measured, independent and observed [I > 2σ(I)] reflections	12006, 4140, 2888	18107, 4204, 3839
R int	0.101	0.092
(sin θ/λ)max (Å−1)	0.645	0.634
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.082, 0.244, 1.04	0.048, 0.129, 1.06
No. of reflections	4140	4204
No. of parameters	267	276
No. of restraints	0	4
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement	H atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å−3)	0.57, −0.83	0.31, −0.25

Computer programs: MarCCD (Doyle, 2011 ▸), iMosflm (Battye et al., 2011 ▸), SHELXT (Sheldrick, 2015a ▸), SHELXL2014 (Sheldrick, 2015b ▸) and SHELXTL (Sheldrick, 2008 ▸).

The COOH-group in II is disordered over two orientations. The refinement of their occupancy factors was unstable, thus the occupancies were constrained to a 0.6:0.4 ratio. The two positions of this group were refined at fixed C=O and C—O distances of 1.210 (3) and 1.320 (3) Å, respectively. Moreover, the anisotropic displacement parameters for the oxygen atoms of the C=O and C—O groups were restrained to be equal.

The hydrogen atoms of the OH groups were localized in difference-Fourier maps and refined isotropically with fixed displacement parameters [U _iso(H) = 1.5U _eq(O)]. The other hydrogen atoms were placed in calculated positions with C—H = 0.95–1.00 Å and refined using the riding model with fixed isotropic displacement parameters [U _iso(H) = 1.5U _eq(C) for the CH₃ groups and 1.2U _eq(C) for all others].

A relatively large number of reflections (a few dozen) were omitted for the following reasons: (1) In order to achieve better I/σ statistics for high-angle reflections we selected a larger exposure time, which resulted in some intensity overloads in the low-angle part of the area. These corrupted intensities were excluded from the final steps of the refinement. (2) In the current setup of the instrument, the low-temperature device eclipses a small region of the detector near its high-angle limit. This resulted in zero intensity for some reflections. (3) The quality of the single crystals chosen for the diffraction experiments was far from perfect. Some systematic intensity deviations can be due to extinction and defects present in the crystals.

Supplementary Material

CCDC references: 1864385, 1864384

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

(3aSR,4RS,4aRS,7aSR)-5-Oxothieno[2,3-f]isoindole-4-carboxylic acid (I) . Crystal data

C24H21NO3S	F(000) = 848
Mr = 403.48	Dx = 1.327 Mg m−3
Monoclinic, P21/n	Synchrotron radiation, λ = 0.96260 Å
a = 14.572 (3) Å	Cell parameters from 600 reflections
b = 8.7989 (18) Å	θ = 3.6–36.0°
c = 16.982 (3) Å	µ = 0.41 mm−1
β = 111.92 (3)°	T = 100 K
V = 2020.0 (8) Å3	Prism, colourless
Z = 4	0.15 × 0.10 × 0.10 mm

(3aSR,4RS,4aRS,7aSR)-5-Oxothieno[2,3-f]isoindole-4-carboxylic acid (I) . Data collection

Rayonix SX165 CCD diffractometer	2888 reflections with I > 2σ(I)
/f scan	Rint = 0.101
Absorption correction: multi-scan (SCALA; Evans, 2006)	θmax = 38.4°, θmin = 3.6°
Tmin = 0.930, Tmax = 0.950	h = −12→18
12006 measured reflections	k = −10→8
4140 independent reflections	l = −21→14

(3aSR,4RS,4aRS,7aSR)-5-Oxothieno[2,3-f]isoindole-4-carboxylic acid (I) . Refinement

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.082	H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.244	w = 1/[σ2(Fo2) + (0.08P)2 + 4P] where P = (Fo2 + 2Fc2)/3
S = 1.04	(Δ/σ)max < 0.001
4140 reflections	Δρmax = 0.57 e Å−3
267 parameters	Δρmin = −0.83 e Å−3
0 restraints	Extinction correction: SHELXL (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: difference Fourier map	Extinction coefficient: 0.027 (4)

(3aSR,4RS,4aRS,7aSR)-5-Oxothieno[2,3-f]isoindole-4-carboxylic acid (I) . Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

(3aSR,4RS,4aRS,7aSR)-5-Oxothieno[2,3-f]isoindole-4-carboxylic acid (I) . Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
S1	0.70674 (7)	0.54365 (14)	0.24110 (6)	0.0381 (4)
C2	0.6019 (3)	0.5821 (5)	0.1467 (3)	0.0360 (10)
C3	0.5152 (3)	0.5575 (5)	0.1543 (2)	0.0337 (9)
H3	0.4540	0.5694	0.1079	0.040*
C3A	0.5203 (3)	0.5094 (5)	0.2417 (2)	0.0288 (8)
H3A	0.4993	0.6007	0.2658	0.035*
C4	0.4494 (2)	0.3754 (4)	0.2477 (2)	0.0253 (8)
C4A	0.4981 (2)	0.3035 (4)	0.3372 (2)	0.0249 (8)
H4A	0.5376	0.2153	0.3299	0.030*
C5	0.4338 (3)	0.2403 (4)	0.3820 (2)	0.0243 (8)
O3	0.35066 (18)	0.1829 (3)	0.34752 (14)	0.0299 (7)
N6	0.4879 (2)	0.2501 (4)	0.46806 (17)	0.0274 (7)
C7	0.5884 (3)	0.3135 (5)	0.4862 (2)	0.0295 (9)
H7A	0.6378	0.2318	0.4942	0.035*
H7B	0.6097	0.3795	0.5371	0.035*
C7A	0.5723 (2)	0.4056 (4)	0.4050 (2)	0.0248 (8)
H7C	0.5384	0.5029	0.4081	0.030*
C8	0.6579 (3)	0.4419 (5)	0.3776 (2)	0.0305 (9)
H8	0.7252	0.4334	0.4146	0.037*
C8A	0.6300 (3)	0.4869 (5)	0.2967 (2)	0.0302 (9)
C9	0.6196 (4)	0.6459 (6)	0.0702 (3)	0.0494 (12)
H9A	0.6507	0.7462	0.0844	0.074*
H9B	0.5563	0.6553	0.0223	0.074*
H9C	0.6633	0.5773	0.0549	0.074*
C10	0.3550 (3)	0.4624 (4)	0.2411 (2)	0.0243 (8)
O1	0.33975 (18)	0.5090 (3)	0.30274 (15)	0.0303 (7)
O2	0.29599 (19)	0.4951 (3)	0.16006 (15)	0.0294 (6)
H2	0.240 (3)	0.567 (5)	0.161 (3)	0.044*
C11	0.4327 (2)	0.2480 (5)	0.1814 (2)	0.0258 (8)
C12	0.3445 (3)	0.1640 (4)	0.1514 (2)	0.0263 (8)
H12	0.2902	0.1956	0.1656	0.032*
C13	0.3348 (3)	0.0346 (5)	0.1011 (2)	0.0305 (9)
H13	0.2747	−0.0213	0.0819	0.037*
C14	0.4136 (3)	−0.0122 (5)	0.0790 (2)	0.0326 (9)
H14	0.4070	−0.0992	0.0441	0.039*
C15	0.5016 (3)	0.0688 (5)	0.1082 (2)	0.0338 (10)
H15	0.5554	0.0364	0.0936	0.041*
C16	0.5118 (3)	0.1985 (4)	0.1591 (2)	0.0270 (8)
H16	0.5724	0.2531	0.1786	0.032*
C17	0.4580 (3)	0.1950 (4)	0.5344 (2)	0.0270 (8)
C18	0.5317 (3)	0.1501 (5)	0.6121 (2)	0.0324 (9)
H18	0.5993	0.1491	0.6185	0.039*
C19	0.5044 (3)	0.1070 (5)	0.6798 (2)	0.0383 (10)
H19	0.5539	0.0761	0.7320	0.046*
C20	0.4059 (3)	0.1088 (5)	0.6717 (2)	0.0372 (10)
H20	0.3882	0.0816	0.7183	0.045*
C21	0.3333 (3)	0.1510 (5)	0.5943 (2)	0.0362 (10)
H21	0.2658	0.1505	0.5882	0.043*
C22	0.3584 (3)	0.1941 (5)	0.5253 (2)	0.0323 (9)
H22	0.3083	0.2225	0.4729	0.039*

(3aSR,4RS,4aRS,7aSR)-5-Oxothieno[2,3-f]isoindole-4-carboxylic acid (I) . Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
S1	0.0248 (6)	0.0533 (8)	0.0398 (6)	−0.0065 (5)	0.0164 (5)	0.0001 (5)
C2	0.030 (2)	0.041 (2)	0.042 (2)	0.0030 (19)	0.0195 (18)	0.0056 (18)
C3	0.024 (2)	0.041 (3)	0.037 (2)	0.0027 (18)	0.0123 (17)	0.0063 (17)
C3A	0.0218 (18)	0.032 (2)	0.0324 (18)	0.0015 (16)	0.0094 (15)	0.0003 (16)
C4	0.0166 (17)	0.035 (2)	0.0225 (15)	0.0000 (15)	0.0049 (14)	0.0036 (15)
C4A	0.0176 (17)	0.034 (2)	0.0223 (16)	0.0016 (16)	0.0063 (14)	−0.0051 (15)
C5	0.0204 (17)	0.028 (2)	0.0212 (15)	−0.0020 (15)	0.0043 (14)	−0.0019 (14)
O3	0.0221 (14)	0.0400 (17)	0.0245 (12)	−0.0068 (12)	0.0053 (10)	0.0024 (11)
N6	0.0190 (15)	0.043 (2)	0.0190 (13)	−0.0002 (14)	0.0056 (12)	−0.0012 (13)
C7	0.0196 (18)	0.042 (2)	0.0233 (16)	−0.0007 (17)	0.0041 (14)	−0.0066 (16)
C7A	0.0179 (17)	0.027 (2)	0.0270 (17)	−0.0019 (15)	0.0056 (14)	−0.0040 (15)
C8	0.0168 (17)	0.042 (2)	0.0301 (18)	−0.0045 (16)	0.0053 (15)	−0.0097 (16)
C8A	0.0248 (19)	0.031 (2)	0.0369 (19)	−0.0017 (17)	0.0136 (16)	−0.0052 (16)
C9	0.047 (3)	0.053 (3)	0.056 (3)	0.000 (2)	0.029 (2)	0.017 (2)
C10	0.0163 (17)	0.032 (2)	0.0226 (15)	−0.0054 (15)	0.0052 (14)	−0.0008 (14)
O1	0.0252 (14)	0.0393 (17)	0.0279 (12)	0.0035 (12)	0.0117 (11)	−0.0030 (11)
O2	0.0220 (13)	0.0398 (17)	0.0251 (12)	0.0064 (12)	0.0073 (10)	0.0021 (11)
C11	0.0198 (17)	0.038 (2)	0.0194 (15)	0.0005 (16)	0.0070 (13)	0.0056 (15)
C12	0.0221 (18)	0.034 (2)	0.0213 (15)	0.0016 (16)	0.0066 (14)	0.0011 (14)
C13	0.029 (2)	0.036 (2)	0.0223 (16)	0.0002 (17)	0.0043 (15)	0.0001 (15)
C14	0.042 (2)	0.034 (2)	0.0204 (16)	0.0033 (19)	0.0101 (16)	−0.0011 (15)
C15	0.035 (2)	0.045 (3)	0.0249 (17)	0.0068 (19)	0.0162 (17)	0.0013 (17)
C16	0.0240 (19)	0.035 (2)	0.0233 (16)	0.0004 (16)	0.0099 (14)	0.0027 (15)
C17	0.031 (2)	0.029 (2)	0.0221 (16)	0.0044 (16)	0.0110 (15)	−0.0002 (14)
C18	0.032 (2)	0.037 (2)	0.0258 (17)	0.0047 (18)	0.0074 (16)	−0.0002 (16)
C19	0.050 (3)	0.036 (2)	0.0252 (18)	0.005 (2)	0.0096 (18)	0.0008 (16)
C20	0.052 (3)	0.038 (2)	0.0273 (18)	0.000 (2)	0.0204 (18)	−0.0008 (16)
C21	0.037 (2)	0.040 (3)	0.035 (2)	−0.0058 (19)	0.0174 (18)	−0.0024 (17)
C22	0.035 (2)	0.038 (2)	0.0254 (17)	0.0021 (18)	0.0133 (16)	−0.0007 (16)

(3aSR,4RS,4aRS,7aSR)-5-Oxothieno[2,3-f]isoindole-4-carboxylic acid (I) . Geometric parameters (Å, º)

S1—C8A	1.782 (4)	C9—H9B	0.9800
S1—C2	1.785 (4)	C9—H9C	0.9800
C2—C3	1.335 (5)	C10—O1	1.219 (4)
C2—C9	1.523 (6)	C10—O2	1.353 (4)
C3—C3A	1.519 (5)	O2—H2	1.04 (5)
C3—H3	0.9500	C11—C12	1.404 (5)
C3A—C8A	1.534 (5)	C11—C16	1.409 (5)
C3A—C4	1.596 (5)	C12—C13	1.399 (5)
C3A—H3A	1.0000	C12—H12	0.9500
C4—C10	1.542 (5)	C13—C14	1.397 (5)
C4—C11	1.543 (5)	C13—H13	0.9500
C4—C4A	1.551 (5)	C14—C15	1.387 (6)
C4A—C5	1.517 (5)	C14—H14	0.9500
C4A—C7A	1.541 (5)	C15—C16	1.406 (5)
C4A—H4A	1.0000	C15—H15	0.9500
C5—O3	1.239 (4)	C16—H16	0.9500
C5—N6	1.379 (4)	C17—C22	1.400 (5)
N6—C17	1.435 (4)	C17—C18	1.412 (5)
N6—C7	1.488 (4)	C18—C19	1.401 (5)
C7—C7A	1.540 (5)	C18—H18	0.9500
C7—H7A	0.9900	C19—C20	1.390 (6)
C7—H7B	0.9900	C19—H19	0.9500
C7A—C8	1.519 (5)	C20—C21	1.394 (6)
C7A—H7C	1.0000	C20—H20	0.9500
C8—C8A	1.340 (5)	C21—C22	1.404 (5)
C8—H8	0.9500	C21—H21	0.9500
C9—H9A	0.9800	C22—H22	0.9500
C8A—S1—C2	91.87 (18)	C3A—C8A—S1	111.1 (3)
C3—C2—C9	127.6 (4)	C2—C9—H9A	109.5
C3—C2—S1	114.0 (3)	C2—C9—H9B	109.5
C9—C2—S1	118.3 (3)	H9A—C9—H9B	109.5
C2—C3—C3A	115.9 (4)	C2—C9—H9C	109.5
C2—C3—H3	122.1	H9A—C9—H9C	109.5
C3A—C3—H3	122.1	H9B—C9—H9C	109.5
C3—C3A—C8A	106.9 (3)	O1—C10—O2	123.5 (3)
C3—C3A—C4	118.1 (3)	O1—C10—C4	123.2 (3)
C8A—C3A—C4	114.8 (3)	O2—C10—C4	113.0 (3)
C3—C3A—H3A	105.3	C10—O2—H2	108 (2)
C8A—C3A—H3A	105.3	C12—C11—C16	118.0 (3)
C4—C3A—H3A	105.3	C12—C11—C4	121.4 (3)
C10—C4—C11	114.5 (3)	C16—C11—C4	120.0 (3)
C10—C4—C4A	110.1 (3)	C13—C12—C11	121.3 (3)
C11—C4—C4A	107.9 (3)	C13—C12—H12	119.3
C10—C4—C3A	102.1 (3)	C11—C12—H12	119.3
C11—C4—C3A	114.8 (3)	C14—C13—C12	119.9 (4)
C4A—C4—C3A	107.0 (3)	C14—C13—H13	120.0
C5—C4A—C7A	103.3 (3)	C12—C13—H13	120.0
C5—C4A—C4	119.9 (3)	C15—C14—C13	119.7 (4)
C7A—C4A—C4	115.5 (3)	C15—C14—H14	120.2
C5—C4A—H4A	105.6	C13—C14—H14	120.2
C7A—C4A—H4A	105.6	C14—C15—C16	120.5 (3)
C4—C4A—H4A	105.6	C14—C15—H15	119.7
O3—C5—N6	126.7 (3)	C16—C15—H15	119.7
O3—C5—C4A	126.1 (3)	C15—C16—C11	120.5 (3)
N6—C5—C4A	107.1 (3)	C15—C16—H16	119.8
C5—N6—C17	126.1 (3)	C11—C16—H16	119.8
C5—N6—C7	111.8 (3)	C22—C17—C18	119.7 (3)
C17—N6—C7	121.9 (3)	C22—C17—N6	121.4 (3)
N6—C7—C7A	101.7 (3)	C18—C17—N6	118.7 (3)
N6—C7—H7A	111.4	C19—C18—C17	119.6 (4)
C7A—C7—H7A	111.4	C19—C18—H18	120.2
N6—C7—H7B	111.4	C17—C18—H18	120.2
C7A—C7—H7B	111.4	C20—C19—C18	120.9 (4)
H7A—C7—H7B	109.3	C20—C19—H19	119.5
C8—C7A—C7	121.1 (3)	C18—C19—H19	119.5
C8—C7A—C4A	108.7 (3)	C19—C20—C21	119.2 (3)
C7—C7A—C4A	101.0 (3)	C19—C20—H20	120.4
C8—C7A—H7C	108.4	C21—C20—H20	120.4
C7—C7A—H7C	108.4	C20—C21—C22	121.0 (4)
C4A—C7A—H7C	108.4	C20—C21—H21	119.5
C8A—C8—C7A	114.0 (3)	C22—C21—H21	119.5
C8A—C8—H8	123.0	C17—C22—C21	119.5 (4)
C7A—C8—H8	123.0	C17—C22—H22	120.3
C8—C8A—C3A	120.7 (3)	C21—C22—H22	120.3
C8—C8A—S1	128.0 (3)
C8A—S1—C2—C3	0.8 (4)	C3—C3A—C8A—C8	−179.1 (4)
C8A—S1—C2—C9	177.4 (4)	C4—C3A—C8A—C8	−46.1 (5)
C9—C2—C3—C3A	−173.4 (4)	C3—C3A—C8A—S1	5.9 (4)
S1—C2—C3—C3A	2.9 (5)	C4—C3A—C8A—S1	139.0 (3)
C2—C3—C3A—C8A	−5.7 (5)	C2—S1—C8A—C8	−178.5 (4)
C2—C3—C3A—C4	−136.9 (4)	C2—S1—C8A—C3A	−4.0 (3)
C3—C3A—C4—C10	−88.3 (4)	C11—C4—C10—O1	143.8 (4)
C8A—C3A—C4—C10	144.2 (3)	C4A—C4—C10—O1	22.0 (5)
C3—C3A—C4—C11	36.3 (5)	C3A—C4—C10—O1	−91.4 (4)
C8A—C3A—C4—C11	−91.3 (4)	C11—C4—C10—O2	−42.6 (4)
C3—C3A—C4—C4A	156.0 (3)	C4A—C4—C10—O2	−164.4 (3)
C8A—C3A—C4—C4A	28.5 (4)	C3A—C4—C10—O2	82.2 (3)
C10—C4—C4A—C5	36.4 (4)	C10—C4—C11—C12	−32.8 (4)
C11—C4—C4A—C5	−89.2 (4)	C4A—C4—C11—C12	90.2 (4)
C3A—C4—C4A—C5	146.7 (3)	C3A—C4—C11—C12	−150.6 (3)
C10—C4—C4A—C7A	−88.3 (3)	C10—C4—C11—C16	156.6 (3)
C11—C4—C4A—C7A	146.1 (3)	C4A—C4—C11—C16	−80.3 (4)
C3A—C4—C4A—C7A	22.0 (4)	C3A—C4—C11—C16	38.9 (4)
C7A—C4A—C5—O3	161.3 (4)	C16—C11—C12—C13	0.2 (5)
C4—C4A—C5—O3	31.0 (6)	C4—C11—C12—C13	−170.6 (3)
C7A—C4A—C5—N6	−22.5 (4)	C11—C12—C13—C14	−0.7 (5)
C4—C4A—C5—N6	−152.8 (3)	C12—C13—C14—C15	0.9 (5)
O3—C5—N6—C17	0.1 (6)	C13—C14—C15—C16	−0.6 (5)
C4A—C5—N6—C17	−176.1 (3)	C14—C15—C16—C11	0.1 (5)
O3—C5—N6—C7	174.8 (4)	C12—C11—C16—C15	0.1 (5)
C4A—C5—N6—C7	−1.4 (4)	C4—C11—C16—C15	171.0 (3)
C5—N6—C7—C7A	24.6 (4)	C5—N6—C17—C22	−32.3 (6)
C17—N6—C7—C7A	−160.5 (3)	C7—N6—C17—C22	153.5 (4)
N6—C7—C7A—C8	−156.3 (3)	C5—N6—C17—C18	151.7 (4)
N6—C7—C7A—C4A	−36.3 (3)	C7—N6—C17—C18	−22.4 (5)
C5—C4A—C7A—C8	164.7 (3)	C22—C17—C18—C19	−0.8 (6)
C4—C4A—C7A—C8	−62.4 (4)	N6—C17—C18—C19	175.2 (4)
C5—C4A—C7A—C7	36.2 (3)	C17—C18—C19—C20	−0.4 (6)
C4—C4A—C7A—C7	169.1 (3)	C18—C19—C20—C21	1.4 (6)
C7—C7A—C8—C8A	163.6 (4)	C19—C20—C21—C22	−1.2 (6)
C4A—C7A—C8—C8A	47.5 (5)	C18—C17—C22—C21	1.1 (6)
C7A—C8—C8A—C3A	4.4 (5)	N6—C17—C22—C21	−174.8 (4)
C7A—C8—C8A—S1	178.4 (3)	C20—C21—C22—C17	−0.1 (6)

(3aSR,4RS,4aRS,7aSR)-5-Oxothieno[2,3-f]isoindole-4-carboxylic acid (I) . Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O3i	1.04 (5)	1.63 (5)	2.667 (4)	174 (4)

Symmetry code: (i) −x+1/2, y+1/2, −z+1/2.

(3aSR,4SR,4aRS,7aSR)-5-Oxofuro[2,3-f]isoindole-4-carboxylic acid (II) . Crystal data

C24H21NO4	Z = 2
Mr = 387.42	F(000) = 408
Triclinic, P1	Dx = 1.294 Mg m−3
a = 8.1851 (16) Å	Synchrotron radiation, λ = 0.81182 Å
b = 11.025 (2) Å	Cell parameters from 600 reflections
c = 11.795 (2) Å	θ = 3.5–30.0°
α = 99.14 (3)°	µ = 0.12 mm−1
β = 92.51 (3)°	T = 100 K
γ = 107.99 (3)°	Prism, colourless
V = 994.6 (4) Å3	0.20 × 0.12 × 0.08 mm

(3aSR,4SR,4aRS,7aSR)-5-Oxofuro[2,3-f]isoindole-4-carboxylic acid (II) . Data collection

Rayonix SX165 CCD diffractometer	3839 reflections with I > 2σ(I)
/f scan	Rint = 0.092
Absorption correction: multi-scan (SCALA; Evans, 2006)	θmax = 31.0°, θmin = 3.4°
Tmin = 0.963, Tmax = 0.987	h = −10→10
18107 measured reflections	k = −13→13
4204 independent reflections	l = −14→14

(3aSR,4SR,4aRS,7aSR)-5-Oxofuro[2,3-f]isoindole-4-carboxylic acid (II) . Refinement

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: mixed
R[F2 > 2σ(F2)] = 0.048	H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.129	w = 1/[σ2(Fo2) + (0.0543P)2 + 0.2912P] where P = (Fo2 + 2Fc2)/3
S = 1.06	(Δ/σ)max < 0.001
4204 reflections	Δρmax = 0.31 e Å−3
276 parameters	Δρmin = −0.25 e Å−3
4 restraints	Extinction correction: SHELXL2014 (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: difference Fourier map	Extinction coefficient: 0.060 (10)

(3aSR,4SR,4aRS,7aSR)-5-Oxofuro[2,3-f]isoindole-4-carboxylic acid (II) . Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

(3aSR,4SR,4aRS,7aSR)-5-Oxofuro[2,3-f]isoindole-4-carboxylic acid (II) . Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
O1	0.35211 (12)	−0.05879 (8)	0.66567 (7)	0.0201 (2)
O2	0.5385 (4)	0.4663 (2)	0.8623 (2)	0.0241 (6)	0.6
O3	0.5530 (4)	0.35005 (19)	1.00161 (16)	0.0201 (5)	0.6
H3B	0.520 (4)	0.413 (3)	1.044 (3)	0.030*	0.6
O2'	0.5693 (7)	0.3756 (4)	0.9980 (2)	0.0241 (6)	0.4
O3'	0.5162 (7)	0.4567 (4)	0.8431 (3)	0.0201 (5)	0.4
H3C	0.480 (6)	0.505 (4)	0.901 (4)	0.030*	0.4
O4	0.87874 (12)	0.52722 (8)	0.76246 (7)	0.0223 (2)
C2	0.35057 (15)	−0.07054 (12)	0.78383 (10)	0.0190 (3)
C3	0.39805 (15)	0.04459 (11)	0.85592 (10)	0.0187 (3)
H3	0.4076	0.0566	0.9378	0.022*
C3A	0.43406 (15)	0.15241 (11)	0.78540 (10)	0.0169 (3)
H3A	0.3397	0.1921	0.7944	0.020*
C4	0.61590 (15)	0.26934 (10)	0.81143 (9)	0.0148 (2)
C4A	0.66305 (14)	0.30967 (10)	0.69318 (9)	0.0145 (2)
H4A	0.7364	0.2566	0.6627	0.017*
C5	0.76917 (15)	0.44984 (11)	0.68806 (10)	0.0163 (3)
N6	0.72662 (13)	0.46920 (9)	0.57808 (8)	0.0168 (2)
C7	0.60501 (15)	0.34914 (11)	0.50551 (10)	0.0174 (3)
H7A	0.6678	0.2984	0.4593	0.021*
H7B	0.5233	0.3697	0.4533	0.021*
C7A	0.51119 (14)	0.27614 (11)	0.59767 (10)	0.0155 (3)
H7C	0.4223	0.3152	0.6266	0.019*
C8	0.43213 (15)	0.12915 (11)	0.56824 (10)	0.0175 (3)
H8	0.4044	0.0814	0.4916	0.021*
C8A	0.40597 (15)	0.07445 (11)	0.66291 (10)	0.0165 (3)
C9	0.30386 (19)	−0.20751 (12)	0.80397 (11)	0.0254 (3)
H9A	0.1880	−0.2570	0.7663	0.038*
H9B	0.3056	−0.2078	0.8871	0.038*
H9C	0.3874	−0.2473	0.7717	0.038*
C10	0.56971 (15)	0.37472 (10)	0.89451 (9)	0.0163 (3)
C11	0.76528 (15)	0.23063 (11)	0.86340 (10)	0.0157 (3)
C12	0.78551 (16)	0.10987 (11)	0.81712 (10)	0.0181 (3)
H12	0.7030	0.0516	0.7581	0.022*
C13	0.92622 (17)	0.07539 (12)	0.85763 (11)	0.0223 (3)
H13	0.9373	−0.0063	0.8266	0.027*
C14	1.04993 (17)	0.16108 (13)	0.94346 (11)	0.0243 (3)
H14	1.1443	0.1373	0.9712	0.029*
C15	1.03410 (17)	0.28250 (13)	0.98856 (11)	0.0235 (3)
H15	1.1188	0.3415	1.0459	0.028*
C16	0.89229 (16)	0.31656 (11)	0.94849 (10)	0.0189 (3)
H16	0.8823	0.3987	0.9794	0.023*
C17	0.81267 (15)	0.58110 (11)	0.53022 (10)	0.0175 (3)
C18	0.87154 (17)	0.70563 (12)	0.60084 (11)	0.0216 (3)
H18	0.8574	0.7155	0.6809	0.026*
C19	0.95104 (17)	0.81456 (12)	0.55163 (12)	0.0250 (3)
H19	0.9921	0.8980	0.5992	0.030*
C20	0.97049 (17)	0.80153 (12)	0.43305 (12)	0.0249 (3)
H20	1.0234	0.8759	0.4005	0.030*
C21	0.91129 (16)	0.67809 (12)	0.36291 (11)	0.0226 (3)
H21	0.9237	0.6690	0.2826	0.027*
C22	0.83345 (15)	0.56730 (12)	0.41117 (11)	0.0197 (3)
H22	0.7952	0.4838	0.3637	0.024*

(3aSR,4SR,4aRS,7aSR)-5-Oxofuro[2,3-f]isoindole-4-carboxylic acid (II) . Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
O1	0.0251 (5)	0.0155 (4)	0.0175 (4)	0.0025 (3)	0.0019 (3)	0.0051 (3)
O2	0.0368 (12)	0.0244 (9)	0.0186 (11)	0.0183 (8)	0.0076 (8)	0.0064 (7)
O3	0.0347 (11)	0.0239 (10)	0.0123 (8)	0.0210 (9)	0.0104 (6)	0.0078 (6)
O2'	0.0368 (12)	0.0244 (9)	0.0186 (11)	0.0183 (8)	0.0076 (8)	0.0064 (7)
O3'	0.0347 (11)	0.0239 (10)	0.0123 (8)	0.0210 (9)	0.0104 (6)	0.0078 (6)
O4	0.0264 (5)	0.0184 (4)	0.0182 (4)	0.0030 (3)	0.0001 (4)	0.0016 (3)
C2	0.0186 (6)	0.0206 (6)	0.0189 (6)	0.0054 (4)	0.0048 (4)	0.0077 (4)
C3	0.0189 (6)	0.0211 (6)	0.0173 (6)	0.0065 (5)	0.0054 (4)	0.0059 (4)
C3A	0.0168 (5)	0.0173 (5)	0.0175 (6)	0.0057 (4)	0.0044 (4)	0.0042 (4)
C4	0.0173 (5)	0.0140 (5)	0.0140 (5)	0.0060 (4)	0.0042 (4)	0.0026 (4)
C4A	0.0161 (5)	0.0152 (5)	0.0140 (5)	0.0072 (4)	0.0036 (4)	0.0031 (4)
C5	0.0181 (6)	0.0163 (5)	0.0158 (6)	0.0072 (4)	0.0041 (4)	0.0026 (4)
N6	0.0194 (5)	0.0144 (5)	0.0169 (5)	0.0050 (4)	0.0029 (4)	0.0043 (4)
C7	0.0195 (6)	0.0168 (5)	0.0157 (5)	0.0049 (4)	0.0014 (4)	0.0043 (4)
C7A	0.0154 (5)	0.0165 (5)	0.0162 (5)	0.0064 (4)	0.0020 (4)	0.0048 (4)
C8	0.0172 (5)	0.0177 (5)	0.0168 (6)	0.0051 (4)	−0.0005 (4)	0.0024 (4)
C8A	0.0150 (5)	0.0143 (5)	0.0198 (6)	0.0040 (4)	0.0018 (4)	0.0033 (4)
C9	0.0323 (7)	0.0201 (6)	0.0227 (6)	0.0044 (5)	0.0040 (5)	0.0080 (5)
C10	0.0180 (6)	0.0171 (5)	0.0153 (6)	0.0075 (4)	0.0037 (4)	0.0034 (4)
C11	0.0184 (6)	0.0168 (5)	0.0144 (5)	0.0070 (4)	0.0061 (4)	0.0060 (4)
C12	0.0206 (6)	0.0181 (5)	0.0175 (6)	0.0084 (4)	0.0043 (4)	0.0034 (4)
C13	0.0268 (7)	0.0237 (6)	0.0232 (6)	0.0150 (5)	0.0070 (5)	0.0086 (5)
C14	0.0229 (6)	0.0361 (7)	0.0215 (6)	0.0165 (5)	0.0054 (5)	0.0121 (5)
C15	0.0198 (6)	0.0325 (7)	0.0177 (6)	0.0084 (5)	0.0011 (5)	0.0035 (5)
C16	0.0198 (6)	0.0200 (6)	0.0171 (6)	0.0069 (5)	0.0038 (4)	0.0020 (4)
C17	0.0155 (5)	0.0177 (5)	0.0222 (6)	0.0071 (4)	0.0037 (4)	0.0077 (4)
C18	0.0237 (6)	0.0190 (6)	0.0231 (6)	0.0074 (5)	0.0027 (5)	0.0054 (5)
C19	0.0237 (6)	0.0170 (6)	0.0346 (7)	0.0060 (5)	0.0028 (5)	0.0068 (5)
C20	0.0201 (6)	0.0230 (6)	0.0371 (7)	0.0089 (5)	0.0089 (5)	0.0154 (5)
C21	0.0203 (6)	0.0277 (6)	0.0260 (7)	0.0117 (5)	0.0088 (5)	0.0131 (5)
C22	0.0189 (6)	0.0210 (6)	0.0224 (6)	0.0091 (5)	0.0048 (5)	0.0070 (4)

(3aSR,4SR,4aRS,7aSR)-5-Oxofuro[2,3-f]isoindole-4-carboxylic acid (II) . Geometric parameters (Å, º)

O1—C8A	1.4034 (14)	C7A—H7C	1.0000
O1—C2	1.4203 (14)	C8—C8A	1.3460 (17)
O2—C10	1.226 (2)	C8—H8	0.9500
O3—C10	1.3378 (19)	C9—H9A	0.9800
O3—H3B	0.91 (3)	C9—H9B	0.9800
O2'—C10	1.219 (3)	C9—H9C	0.9800
O3'—C10	1.331 (3)	C11—C16	1.4083 (18)
O3'—H3C	0.91 (5)	C11—C12	1.4181 (16)
O4—C5	1.2339 (16)	C12—C13	1.4069 (17)
C2—C3	1.3447 (18)	C12—H12	0.9500
C2—C9	1.4994 (16)	C13—C14	1.399 (2)
C3—C3A	1.5202 (16)	C13—H13	0.9500
C3—H3	0.9500	C14—C15	1.4066 (19)
C3A—C8A	1.5274 (17)	C14—H14	0.9500
C3A—C4	1.6187 (17)	C15—C16	1.4104 (18)
C3A—H3A	1.0000	C15—H15	0.9500
C4—C11	1.5469 (16)	C16—H16	0.9500
C4—C10	1.5475 (15)	C17—C22	1.4118 (17)
C4—C4A	1.5590 (15)	C17—C18	1.4154 (18)
C4A—C5	1.5333 (16)	C18—C19	1.4052 (17)
C4A—C7A	1.5530 (17)	C18—H18	0.9500
C4A—H4A	1.0000	C19—C20	1.404 (2)
C5—N6	1.3943 (15)	C19—H19	0.9500
N6—C17	1.4339 (15)	C20—C21	1.404 (2)
N6—C7	1.4922 (16)	C20—H20	0.9500
C7—C7A	1.5455 (16)	C21—C22	1.4120 (17)
C7—H7A	0.9900	C21—H21	0.9500
C7—H7B	0.9900	C22—H22	0.9500
C7A—C8	1.5229 (16)
C8A—O1—C2	106.64 (9)	O1—C8A—C3A	110.05 (10)
C10—O3—H3B	108.7 (19)	C2—C9—H9A	109.5
C10—O3'—H3C	105 (3)	C2—C9—H9B	109.5
C3—C2—O1	113.10 (10)	H9A—C9—H9B	109.5
C3—C2—C9	132.64 (11)	C2—C9—H9C	109.5
O1—C2—C9	114.21 (11)	H9A—C9—H9C	109.5
C2—C3—C3A	109.08 (10)	H9B—C9—H9C	109.5
C2—C3—H3	125.5	O2'—C10—O3'	122.8 (3)
C3A—C3—H3	125.5	O2—C10—O3	123.54 (18)
C3—C3A—C8A	101.04 (9)	O2'—C10—C4	122.2 (2)
C3—C3A—C4	119.58 (10)	O2—C10—C4	122.69 (16)
C8A—C3A—C4	113.14 (10)	O3'—C10—C4	114.8 (2)
C3—C3A—H3A	107.5	O3—C10—C4	113.54 (12)
C8A—C3A—H3A	107.5	C16—C11—C12	118.27 (11)
C4—C3A—H3A	107.5	C16—C11—C4	122.03 (10)
C11—C4—C10	113.00 (9)	C12—C11—C4	119.44 (10)
C11—C4—C4A	108.45 (9)	C13—C12—C11	120.79 (12)
C10—C4—C4A	112.78 (9)	C13—C12—H12	119.6
C11—C4—C3A	113.68 (9)	C11—C12—H12	119.6
C10—C4—C3A	102.35 (9)	C14—C13—C12	120.22 (11)
C4A—C4—C3A	106.37 (9)	C14—C13—H13	119.9
C5—C4A—C7A	104.03 (9)	C12—C13—H13	119.9
C5—C4A—C4	120.24 (10)	C13—C14—C15	119.79 (12)
C7A—C4A—C4	116.57 (9)	C13—C14—H14	120.1
C5—C4A—H4A	104.8	C15—C14—H14	120.1
C7A—C4A—H4A	104.8	C14—C15—C16	119.94 (12)
C4—C4A—H4A	104.8	C14—C15—H15	120.0
O4—C5—N6	126.58 (11)	C16—C15—H15	120.0
O4—C5—C4A	127.39 (10)	C11—C16—C15	120.97 (11)
N6—C5—C4A	105.85 (10)	C11—C16—H16	119.5
C5—N6—C17	124.82 (10)	C15—C16—H16	119.5
C5—N6—C7	112.14 (9)	C22—C17—C18	119.90 (11)
C17—N6—C7	121.96 (9)	C22—C17—N6	119.68 (11)
N6—C7—C7A	101.90 (9)	C18—C17—N6	120.39 (11)
N6—C7—H7A	111.4	C19—C18—C17	119.53 (12)
C7A—C7—H7A	111.4	C19—C18—H18	120.2
N6—C7—H7B	111.4	C17—C18—H18	120.2
C7A—C7—H7B	111.4	C20—C19—C18	120.80 (12)
H7A—C7—H7B	109.3	C20—C19—H19	119.6
C8—C7A—C7	118.78 (10)	C18—C19—H19	119.6
C8—C7A—C4A	108.15 (9)	C21—C20—C19	119.66 (12)
C7—C7A—C4A	100.28 (9)	C21—C20—H20	120.2
C8—C7A—H7C	109.7	C19—C20—H20	120.2
C7—C7A—H7C	109.7	C20—C21—C22	120.33 (12)
C4A—C7A—H7C	109.7	C20—C21—H21	119.8
C8A—C8—C7A	112.47 (10)	C22—C21—H21	119.8
C8A—C8—H8	123.8	C17—C22—C21	119.77 (12)
C7A—C8—H8	123.8	C17—C22—H22	120.1
C8—C8A—O1	126.48 (11)	C21—C22—H22	120.1
C8—C8A—C3A	123.47 (10)
C8A—O1—C2—C3	0.41 (14)	C4—C3A—C8A—C8	−47.35 (15)
C8A—O1—C2—C9	−177.19 (10)	C3—C3A—C8A—O1	2.97 (12)
O1—C2—C3—C3A	1.57 (14)	C4—C3A—C8A—O1	132.04 (10)
C9—C2—C3—C3A	178.61 (13)	C11—C4—C10—O2'	−38.9 (3)
C2—C3—C3A—C8A	−2.68 (13)	C4A—C4—C10—O2'	−162.3 (3)
C2—C3—C3A—C4	−127.51 (11)	C3A—C4—C10—O2'	83.8 (3)
C3—C3A—C4—C11	27.00 (14)	C11—C4—C10—O2	137.8 (2)
C8A—C3A—C4—C11	−91.82 (11)	C4A—C4—C10—O2	14.3 (2)
C3—C3A—C4—C10	−95.20 (11)	C3A—C4—C10—O2	−99.5 (2)
C8A—C3A—C4—C10	145.99 (9)	C11—C4—C10—O3'	146.8 (3)
C3—C3A—C4—C4A	146.28 (10)	C4A—C4—C10—O3'	23.3 (3)
C8A—C3A—C4—C4A	27.46 (12)	C3A—C4—C10—O3'	−90.5 (3)
C11—C4—C4A—C5	−87.06 (12)	C11—C4—C10—O3	−47.5 (2)
C10—C4—C4A—C5	38.87 (14)	C4A—C4—C10—O3	−170.99 (17)
C3A—C4—C4A—C5	150.30 (10)	C3A—C4—C10—O3	75.12 (19)
C11—C4—C4A—C7A	145.69 (9)	C10—C4—C11—C16	−26.72 (14)
C10—C4—C4A—C7A	−88.38 (12)	C4A—C4—C11—C16	99.09 (12)
C3A—C4—C4A—C7A	23.04 (12)	C3A—C4—C11—C16	−142.82 (10)
C7A—C4A—C5—O4	162.69 (11)	C10—C4—C11—C12	159.31 (10)
C4—C4A—C5—O4	29.90 (17)	C4A—C4—C11—C12	−74.88 (13)
C7A—C4A—C5—N6	−21.89 (11)	C3A—C4—C11—C12	43.20 (14)
C4—C4A—C5—N6	−154.68 (10)	C16—C11—C12—C13	1.81 (17)
O4—C5—N6—C17	4.24 (19)	C4—C11—C12—C13	176.01 (10)
C4A—C5—N6—C17	−171.23 (10)	C11—C12—C13—C14	−0.89 (18)
O4—C5—N6—C7	172.53 (11)	C12—C13—C14—C15	−0.55 (18)
C4A—C5—N6—C7	−2.94 (12)	C13—C14—C15—C16	1.02 (19)
C5—N6—C7—C7A	26.50 (12)	C12—C11—C16—C15	−1.34 (17)
C17—N6—C7—C7A	−164.83 (9)	C4—C11—C16—C15	−175.38 (10)
N6—C7—C7A—C8	−154.90 (10)	C14—C15—C16—C11	−0.06 (18)
N6—C7—C7A—C4A	−37.46 (10)	C5—N6—C17—C22	145.02 (12)
C5—C4A—C7A—C8	161.73 (9)	C7—N6—C17—C22	−22.18 (16)
C4—C4A—C7A—C8	−63.41 (12)	C5—N6—C17—C18	−37.12 (17)
C5—C4A—C7A—C7	36.67 (10)	C7—N6—C17—C18	155.69 (11)
C4—C4A—C7A—C7	171.53 (9)	C22—C17—C18—C19	−0.28 (18)
C7—C7A—C8—C8A	159.62 (11)	N6—C17—C18—C19	−178.14 (11)
C4A—C7A—C8—C8A	46.40 (13)	C17—C18—C19—C20	0.93 (19)
C7A—C8—C8A—O1	−172.99 (10)	C18—C19—C20—C21	−0.6 (2)
C7A—C8—C8A—C3A	6.30 (16)	C19—C20—C21—C22	−0.37 (19)
C2—O1—C8A—C8	177.14 (12)	C18—C17—C22—C21	−0.67 (17)
C2—O1—C8A—C3A	−2.22 (12)	N6—C17—C22—C21	177.20 (10)
C3—C3A—C8A—C8	−176.42 (11)	C20—C21—C22—C17	1.00 (18)

(3aSR,4SR,4aRS,7aSR)-5-Oxofuro[2,3-f]isoindole-4-carboxylic acid (II) . Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3B···O2i	0.91 (3)	1.79 (3)	2.692 (3)	176 (3)
O3′—H3C···O2′i	0.91 (5)	1.79 (5)	2.690 (6)	169 (4)

Symmetry code: (i) −x+1, −y+1, −z+2.

Funding Statement

This work was funded by Ministry of Education and Science of the Russian Federation grant 4.1154.2017/4.6. Russian Foundation for Basic Research grant 16-03-00125.