New approach to sugar derivatives by Pummerer reactions of optically active suiphoxide and sulphide having a 7-oxabicyclo[2.2.1]heptane ring system

Abstract

Pummerer reactions of 3-(2-pyridylsulphinyl)-7-oxabicyclo[2.2.1]heptane-2-carboxylate 3 and the corresponding sulphide 4, which were obtained by an asymmetric Diels–Alder reaction of the (S),3-(2-pyridylsulphinyl)acrylate 2 with high diastereoselectivity, gave the β-keto ester 5 and the vinyl sulphide 6 in 62 and 87% yield, respectively. The keto ester 5 was transformed into the C(5) branched-chain sugar derivative 7 by successive Baeyer–Villiger oxidation and stereoselective cleavage of the resulting lactone 16. Dealkoxycarbonylation of the keto ester 5 afforded the 7-oxanorbornanone derivative 8. In addition, upon ozonolysis, the vinyl sulphide 6 was converted into the D-2,5-anhydroallose derivative 9.