Degradation of carbohydrates IV. Formation of cis-unsaturated hexosones

Abstract

Two stereospecific methods are described for the formation of the cis-isomer of unsaturated D-hexosone, 1,5-epoxy-lαβ,6-dihydroxy-D-glycero-hex-cis-3-en-2-one (X). One method is to heat 3-deoxy-D-erythro-hexosone with dilute acid, and the other to treat 2,3-di-0-methyl-D-glucose first with calcium hydroxide then with acid. The 6-methyl ether of (X) is formed from 2,3,6-tri-O-methyl-D-glucose and from 2,3,4,6-tetra-O-methyl-D-glucose by the calcium hydroxide treatment method. The unsaturated osones are probably formed from an intermediate, the enolic form of a 3-deoxyosone, by an acid-catalysed oxotropic rearrangement.