(1R,4′S)-4-(tert-Butyl­dimethyl­silan­oxy)-1-[2,2-dimethyl-3-(p-tolyl­sulfon­yl)-1,3-oxazolidin-4-yl]but-2-yn-1-ol

Jörg Erdsack; Markus Schürmann; Hans Preut; Norbert Krause

doi:10.1107/S1600536808014906

. 2008 May 30;64(Pt 6):o1171. doi: 10.1107/S1600536808014906

(1R,4′S)-4-(tert-Butyldimethylsilanoxy)-1-[2,2-dimethyl-3-(p-tolylsulfonyl)-1,3-oxazolidin-4-yl]but-2-yn-1-ol

Jörg Erdsack ^a, Markus Schürmann ^a, Hans Preut ^a,^*, Norbert Krause ^a

PMCID: PMC2961448 PMID: 21202678

Abstract

The chiral title compound, C₂₂H₃₅NO₅SSi, is a precursor of novel furanomycin derivatives. It crystallizes with two molecules in the asymmetric unit; these show different conformations of the silyl substitutent, as indicated by the Si—O—C—C torsion angles of 41.4 (7) and −84.5 (5)° in the two molecules. The anti configuration of the adjacent stereogenic centers is consistent with the Felkin–Anh model. Each of the two crystallographically independent molecules is connected with a neighbouring molecule of the same type via two symmetry-equivalent O—H⋯O hydrogen bonds.

Related literature

For related literature, see: Anh & Eisenstein (1977 ▶); Chérest et al. (1968 ▶); Deutsch et al. (2008 ▶); Erdsack & Krause (2008 ▶); Garner & Park (1987 ▶); Hoffmann-Röder & Krause (2001 ▶); Kim & Rhee (2000 ▶).

Experimental

Crystal data

C₂₂H₃₅NO₅SSi
M _r = 453.66
Monoclinic,
a = 26.283 (5) Å
b = 11.335 (2) Å
c = 19.219 (4) Å
β = 121.40 (3)°
V = 4887 (2) Å³
Z = 8
Mo Kα radiation
μ = 0.21 mm⁻¹
T = 173 (1) K
0.10 × 0.08 × 0.01 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: none
8353 measured reflections
8353 independent reflections
3487 reflections with I > 2σ(I)
R _int = 0.035

Refinement

R[F ² > 2σ(F ²)] = 0.035
wR(F ²) = 0.087
S = 1.03
8353 reflections
559 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.18 e Å⁻³
Δρ_min = −0.20 e Å⁻³
Absolute structure: Flack (1983 ▶), 3636 Friedel pairs
Flack parameter: −0.09 (7)

Data collection: COLLECT (Nonius, 1998 ▶); cell refinement: DENZO and SCALEPACK (Otwinowski & Minor, 1997 ▶); data reduction: DENZO and SCALEPACK; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL-Plus (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXL97 and PLATON (Spek, 2003 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808014906/hb2724sup1.cif

e-64-o1171-sup1.cif^{(37.1KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808014906/hb2724Isup2.hkl

e-64-o1171-Isup2.hkl^{(408.6KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O4—H4⋯O2ⁱ	0.84	2.01	2.828 (4)	164
O4′—H4′⋯O2′ⁱⁱ	0.84	2.06	2.851 (4)	157

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Symmetry codes: (i) Inline graphic ; (ii) .

supplementary crystallographic information

Comment

The title compound, (I), is a precursor of novel furanomycin derivatives using the gold-catalyzed cyclization of α-hydroxyallenes (Hoffmann-Röder & Krause, 2001; Erdsack & Krause, 2008), which are prepared by S_N2' substitution of propargylic carbonates with catalytic copper hydride (Deutsch et al., 2008). The compound (I) was synthesized by nucleophilic acetylide addition to the tosyl protected analogue of Garner's aldehyde (Kim & Rhee, 2000; Garner & Park, 1987) under non-chelating conditions. A crystal structure determination of (I) has now been carried out to establish the anti configuration of the adjacent stereocenters. Figs. 1 and 2 show that the relative configuration of C12 and C13 in the first molecule and C12' and C13' in the second molecule are as expected.

The compound crystallizes in pairs of molecules, which are different concerning the conformation of the silyl substitutent, as indicated by the Si—O5—C16—C15 and Si'—O5'—C16'—C15' torsion angles of 41.4 (7)° and -84.5 (5)°, respectively. The torsion angles C17—Si—O5—C16 [155.8 (4)°] and C17'—Si'—O5'—C16' [169.9 (4)°] also differ significantly. The preferred gauche conformation of the substitutents O4 and C11 along the newly formed C12—C13 bond is in accordance with the Felkin-Anh model (Chérest et al., 1968; Anh & Eisenstein, 1977). The configuration of the stereogenic centers in (I) (C12 S and C13 R) was assigned based on the starting material (L-serine).

In the crystal, pairs of symmetry equivalent molecules are linked by pairs of O—H···O hydrogen bonds (Table 1).

Experimental

In an oven-dried three-necked 250-ml-flask equipped with a magnetic stirring bar and nitrogen inlet, tert-butyldimethylprop-2-ynyloxysilane (4.68 g, 27.5 mmol) was dissolved in anhydrous THF (95 ml) under argon. After cooling to 243 K, n-BuLi (2.5 M in hexane, 11.0 ml, 27.5 mmol) was added dropwise and stirring was continued for 15 min. Hexamethylphosphoramide (4.78 ml, 27.5 mmol) was added and the solution was cooled to 188 K. After 5 min with stirring, a solution of (S)-2,2-dimethyl-3-(toluene-4-sulfonyl)-oxazolidine-4-carbaldehyde (3.9 g, 13.8 mmol) in anhydrous THF (20 ml) was added slowly by syringe on the inner surface of the flask. After 45 min with stirring at 188 K, TLC showed the complete conversion of starting material. After 60 min total time of stirring, the mixture was poured into aq. sat. NH₄Cl (250 ml). The organic phase was separated and the residue was washed with diethyl ether (3 × 100 ml). The combined organic layers were washed with brine, dried (MgSO₄), filtered, and the solvent was evaporated. The residue was purified by column chromatography (silica gel, isohexane-EtOAc 85:15 → 7:3) to give the title compound (I) (5.13 g, 82%) as a colourless solid. A small sample was recrystallized from isohexane to give colourless blocks and plates of (I) suitable for X-ray analysis; mp 388 K (isohexane); [α]²¹_D -38.6 (c 1.20, CHCl₃); R_f = 0.66 (isohexane-EtOAc 7:3); IR (KBr): 3514, 2984, 2952, 2928, 2885, 2857, 1599, 1471, 1461, 1385, 1339, 1254, 1205, 1159, 1090, 1030, 837, 815, 779, 660, 594 cm^-1; ¹H NMR (400 MHz, CDCl₃): δ (p.p.m.) = 7.73 (d, J = 8.2 Hz, 2 H), 7.29 (d, J = 8.1 Hz, 2 H), 4.73 (d, J = 3.9 Hz, 1 H), 4.30 (d, J = 1.4 Hz, 2 H), 4.20 (dd, J = 4.0, 9.3 Hz, 1 H), 3.96 (dd, J = 7.1, 9.2 Hz, 1 H), 3.79 (m, 1 H), 3.07 (d, J = 6.1 Hz, 1 H), 2.40 (s, 3 H), 1.68 (s, 3 H), 1.50 (s, 3 H), 0.87 (s, 9 H), 0.08 (s, 6 H); ¹³C NMR (100 MHz, CDCl₃): δ (p.p.m.) = 143.8, 136.8, 129.7, 127.5, 99.2, 85.3, 82.0, 65.0, 62.6, 62.5, 51.5, 28.3, 25.7, 24.7, 21.4, 18.2, -5.3; HRMS (ESI): m/z [M + H]⁺ calcd for C₂₂H₃₆NO₅³²S²⁸Si: 454.2078; found 454.2072.