APPLICATIONS OF CYCLIC SULFATES OF VIC-DIOLS - SYNTHESIS OF EPISULFIDES, OLEFINS, AND THIO SUGARS

A new efficient and expeditious one-pot synthesis of thiiranes and ole fins from cyclic sulfates of vic-diols is described. Opening of cyclic sulfates with potassium thioacetate or potassium thiocyanate followed by treatment with sodium methoxide led to episulfides. Olefins were o btained when potassium selenocyanate was used as nucleophile, and the obtained monoesters were treated with sodium borohydride. This method was applied to acyclic polyols derived from chiral glycerine, 1,2-isop ropylidenehexofuranoses with different subtituents at C-3, and dimethy l acetals derived from pentoses and hexoses. The methodology is highly versatile, and its applicability has been demonstrated by the synthes is of different 4- and 5-thiosugars by opening of the thiirane ring wi th sodium acetate or lithium aluminum hydride. Reduction with lithium aluminum hydride of the thiocyanate sulfate potassium salt obtained by the opening of cyclic sulfate with KSCN allowed the direct synthesis of 5-deoxy-4-thio- and 6-deoxy-5-thiosugars. Cyclic thiosugars with th e sulfur atom in the ring are obtained by acidic hydrolysis of the 5-t hiol derivatives of 1,2-O-isopropylidenehexofuranoses and 4-thiopentos e dimethyl acetals. Using this method, an efficient synthesis of 5-thi o-L-fucose as well as the synthesis of 2,5-dideoxy-4-thiofuranose is d escribed.