3,4,6-Tri-O-acetyl-1,2-[(S)-ethyl­idene]-β-d-mannopyran­ose

Henok H Kinfe; Felix L Makolo; Zanele Phasha; Alfred Muller

doi:10.1107/S1600536812032369

. 2012 Jul 21;68(Pt 8):o2520. doi: 10.1107/S1600536812032369

3,4,6-Tri-O-acetyl-1,2-[(S)-ethylidene]-β-d-mannopyranose

Henok H Kinfe ^a, Felix L Makolo ^a, Zanele Phasha ^a, Alfred Muller ^a,^*

PMCID: PMC3414970 PMID: 22904957

Abstract

In the title compound, C₁₄H₂₀O₉, the six-membered pyran and the five-membered dioxalane rings adopt chair and twisted conformations, respectively. In the crystal, the molecules are linked by C—H⋯O interactions.

Related literature

For orthogonal protection in carbohydrate chemistry, see: Wuts & Greene (2007 ▶); Betaneli et al. (1982 ▶). For background to the synthetic methodology, see: Doores et al. (2010 ▶). For ring puckering analysis, see: Cremer & Pople (1975 ▶).

Experimental

Crystal data

C₁₄H₂₀O₉
M _r = 332.3
Orthorhombic,
a = 7.0494 (3) Å
b = 14.6994 (7) Å
c = 15.3608 (7) Å
V = 1591.72 (12) Å³
Z = 4
Cu Kα radiation
μ = 1.01 mm⁻¹
T = 100 K
0.16 × 0.16 × 0.12 mm

Data collection

Bruker APEX DUO 4K-CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2008 ▶) T _min = 0.856, T _max = 0.889
23454 measured reflections
2701 independent reflections
2684 reflections with I > 2σ(I)
R _int = 0.028

Refinement

R[F ² > 2σ(F ²)] = 0.026
wR(F ²) = 0.085
S = 1.20
2701 reflections
212 parameters
H-atom parameters constrained
Δρ_max = 0.26 e Å⁻³
Δρ_min = −0.31 e Å⁻³
Absolute structure: Flack (1983 ▶), 1110 Friedel Pairs
Flack parameter: 0.06 (15)

Data collection: APEX2 (Bruker, 2011 ▶); cell refinement: SAINT (Bruker, 2008 ▶); data reduction: SAINT and XPREP (Bruker, 2008 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg & Putz, 2005 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536812032369/xu5592sup1.cif

e-68-o2520-sup1.cif^{(24.5KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812032369/xu5592Isup2.hkl

e-68-o2520-Isup2.hkl^{(130KB, 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
C1—H1C⋯O3ⁱ	0.98	2.55	3.511 (2)	167
C8—H8⋯O7ⁱ	1.00	2.49	3.317 (2)	140
C12—H12A⋯O4ⁱⁱ	0.98	2.56	3.469 (2)	154
C12—H12B⋯O1ⁱⁱⁱ	0.98	2.51	3.460 (2)	163
C14—H14B⋯O9^iv	0.98	2.53	3.361 (2)	142

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

Acknowledgments

Research funds of the University of Johannesburg and the Research Center for Synthesis and Catalysis are gratefully acknowledged.

supplementary crystallographic information

Comment

Ethylidene acetals are important functional groups for orthogonal protection in carbohydrate chemistry (Wuts & Greene, 2007; Betaneli et al., 1982). The title compound is a key intermediate for the preparation of polysaccharides which exhibit strong activity against the HIV-1 virus (Doores et al., 2010). Herein, we report the crystal structure of 3,4,6-tri-O-acetyl-1,2-O-[S-ethylidene] -β-D-mannopyranoside to confirm its absolute configuration.

The title compound C₁₄H₂₀O₉ (see Fig. 1, and Scheme 1) crystallizes in the P2₁2₁2₁ (Z = 4) space group. Puckering analysis confirms the twisted conformation of the five membered dioxalane ring, with puckering parameter values of q₂ = 0.347 (3) Å, and φ₂ = 61.9 (4)°; and that of the six membered pyran chair conformation ring as q₂ = 0.163 (3) Å, q₃ = -0.526 (3) Å, Q = 0.550 (3) Å and φ₂ = 253.3 (9)° (see Cremer & Pople, 1975). The dioxalane ring is twisted on C6–C7.

The molecules are linked by C-H···O interactions (see Table 1).

Experimental

A solution of 2,3,4,6-tetra-O-acetyl -α-D-mannopyranosyl bromide (150 mg, 0.36 mmol) in acetonitrile (3 ml) was treated with sodium boron hydride (250 mg, 6.61 mmol) and the reaction mixture was stirred at room temperature for 12 h. The mixture was then diluted with chloroform and washed with water three times. The organic layer was dried over anhydrous Na₂SO₄, filtered and evaporated in vacuo to give an oil. The oily residue was crashed with methanol to afford 70% of the target compound as white crystals.

Analytical data: mp: 108-110 °C (Lit. 113-115 °C; Betaneli et al., 1982); ¹H NMR (CDCl₃, 400 MHz): δ 5.40-5.10 (m, 4H), 4.31-4.03 (m, 3H), 3.72-3.64 (m, 1H), 2.09 (s, 3H), 2.04 (s, 3H), 2.02 (s, 3H), 1.51 (d, J = 4.8 Hz, 3H); ¹³C NMR (CDCl₃, 400 MHz): δ 170.7, 170.3, 169.5, 104.8, 96.5, 71.6, 70.6, 66.0, 62.5, 21.6, 20.7, 20.7.