Radical cyclisation reactions leading to doubly branched carbohydrates and 6- and 8-oxygenated 2,9-dioxabicyclo[4.3.0]nonane derivatives

Abstract

2,3-Dideoxy-α-D-erythro-hex-2-enopyranosyl derivatives having, separately, 2-halogenoethyl substituents at O-1 and O-4, on treatment with tri-n-butyltin hydride togerther with a radical promoter, gave products wtih tetrahydrofuranyl rings cis-fused to C-1, C-2 and C-3, C-4, i.e. with branched-points at C-2 and C-3, respectively, and similar reactions in the presence of methyl acrylate or allyltributyltin gave main products with the same bicyclic structures but with additional branch points at C-3 and C-2; when applied to a 2-bromo-1-methoxyethyl 2,3-dideoxyhex-2-enopyranoside and to a 2-bromoethyl 3-deoxyhex-2-enopyranoside the ring closure reactions afforded 8- and 6-oxygenated 2,9-dioxabicyclo[4.3.0]nonane derivatives.