A. Tolstikov, O. Prokopenko, R. K. Yamilov
Jul 1, 1991
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Journal
Bulletin of the Academy of Sciences of the USSR, Division of chemical science
Abstract
In previous works [i, 2], we have shown that the acid cleavage of the dihydropyran ring in hexa-O-acetyl-D-lactal proceeds without breaking the I ~ 4 glycoside bond and leads to an O-glycosylated ~,~-unsaturated diacetoxyaldehyde, whose olefination opens a pathway to the synthesis of O-glycosides with polyhydroxypolyene aglycones. In order to apply this method to solve a specific synthetic problem, namely, the preparation of precursors in the synthesis of cerebrosides, we were the first to carry out analogous transformations for disaccharides with a I ~ 6 glycoside bond. The starting reagent was hexa-O-acetyl-D-gentiobial (II) prepared from available octa-O-acetyl-D-gentiobiose (I) [3] according to a method described for the preparation of tri-O-acetyl-D-glucal [4]. Treatment of (II) with 0.01N sulfuric acid in the presence of HgSO 4 gives 40% (2E,4S,5R)-4-acetoxy-5-hydroxy-6(2,3,4,6-tetra-O-acetyl-~-D-glucopyranyloxy)-2-hexenal (III), which is a convenient structural unit for the synthesis of glycosphyngolipids (IV) [5].