Stereoselective total synthesis of methyl α- d- and α- l-glucopyranosides

Abstract

Methyl α- l- and α- d-glucopyranodsides have been synthesized from mehtyl ( R)- and ( S)-(2-furyl)glycolates ( 3), respectively. The key intermediates, methyl 6- O-benzyl-2,3-dideoxy- l(and d)-hex-2-enopyranosid-4-uloses ( 13), were obtained in the seven steps from the ester 3, without change of configuration of the asymmetric center, which became C-5 in the sugar molecule. Reduction of the ketone group at C-4 in the glycoside 13 with sodium borohydride afforded the corresponding methyl 6- O-benzyl-2,3-dideoxy- erythro-hex-2-enopyranosides ( 14). Epoxidation of the double bond in 14, followed by oxirane ring-opening in the anhydro sugar 16, and subsequent catalytic hydrogenolysis of the benzyl group led to the title compounds.