| Abstract |
The synthesis of new classes of highly functionalized thiosugar derivatives containing alpha,beta-unsaturated carbonyl functions has been accomplished through simple and efficient strategies. 5-Thiosugar-fused butenohdes and a 5-thiohex-1-enopyran-3-ulose were constructed from easily available starting 3-uloses by practical and reliable approaches. The reaction sequence used for the bicyclic fused derivatives involved Wittig olefination of protected pento- or hexofuran-3-uloses, introduction of a sulfhydryl group at C-5 of the intermediate unsaturated ester and acid-promoted deprotection, which allowed intramolecular lactonization and conversion into the 5-thiopyranose form. For the synthesis of a 5thiohex-1-enopyran-3-ulose, a sulfhydryl functionality was introduced at C-5 on a masked 3-ulose derived from 1,2:5,6di-O-isopropylidene-alpha-D-ribo-hexofuranos-3-ulose. Acid hydrolysis displaced the equilibrium towards the 5-thiopentopyran-3-ulose, which on pyridine-mediated acetylation underwent 1,2-ebmination of acetic acid to give the desired alpha,beta-unsaturated 5-thiopyranulose. This straightforward pathway provided the target compound in 37\% overall yield. ((C) Wiley-VCH Verlag GmbH \& Co. KGaA, 69451 Weinheim, Germany, 2009) |
