A Glycosylation Driven Strategy for the Synthesis of Anomerically Pure Vinyl Sulfone-modified Pent-2-enofuranoses and Hex-2-enopyranoses

Abstract

Both α- and β-anomers of vinyl sulfone-modified pent-2-enofuranosides have been synthesized for the first time by taking advantage of the formation of α- and β-methyl glycosides in almost equal ratio only from derivatives of d-xylose. The strategy was equally applicable in the synthesis of α- and β-anomers of vinyl sulfone-modified hex-2-enopyranosides where a d-glucose derivative was selected over a d-allose derivative as the starting material because the former almost exclusively produced the required methyl pyranosides.

modified carbohydrates - Michael acceptors - vinyl sulf­one - pent-2-enofuranoside - hex-2-enopyranoside

References

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25

Analytical and spectroscopic data of selected compounds. 6α: Gummy material. Found: C, 64.48; H, 5.90; S, 8.67. C₂₀H₂₂O₅S requires C, 64.15; H, 5.91; S, 8.56%; ¹H NMR: δ = 6.59 (1 H, s), 5.88 (1 H, d, J = 4.4 Hz), 5.13 (1 H, m), 4.44 (2 H, s, PhCH₂), 3.85 (1 H, dd, J = 10.7, 2.4 Hz), 3.60 (1 H, dd, J = 10.7, 4.4 Hz), 3.39 (3 H, s, OMe), 2.42 (3 H, s, ArMe). 6β: Gummy material. Found: C, 64.41; H, 6.36; S, 8.81. C₂₀H₂₂O₅S requires C, 64.15; H, 5.91; S, 8.56%; ¹H NMR: δ = 6.60 (1 H, s), 5.72 (1 H, s), 4.95 (1 H, d, J = 6.3 Hz), 4.47 (2 H, s, PhCH₂), 3.83 (1 H, dd, J = 10.7, 2.4 Hz), 3.50 (1 H, m), 3.42 (3 H, s, OMe), 2.43 (3 H, s, ArMe). 16: White solid, mp 158-159 °C. Found: C, 56.19; H, 6.90; S, 8.62. C₁₈H₂₄O₇S requires C, 56.23; H, 6.28; S, 8.34%; ¹H NMR: δ = 5.96 (1 H, d, J = 3.9 Hz), 4.96 (1 H, d, J = 3.5 Hz), 1.49 (3 H, s, Me), 1.35 (3 H, s, Me), 1.29 (3 H, s, Me), 1.21 (3 H, s, Me).

26

Compounds 22α and 22β have been synthesized earlier [11] [16a] from d-glucose in 14 steps (7 steps for each anomer). The present method makes use of common intermediates upto compounds 21α and 21β, thereby drastically reducing the overall purification steps. Although overall yields for both the methods are comparable, methyl β-d-glucopyranoside, which has been used in the earlier synthesis, [11] [16a] is far too expensive a starting material to be used in a large-scale multi-step synthesis.

27

The configurations at the C-2 and C-3 positions of 23-25 have been established unambiguously. The data will be published as part of a full paper.