Crystal and molecular structure of a carbohydrate-derived oxetan-3-one. Definitive evidence for a novel participation of a pyranose ring oxygen atom

Abstract

The crystal and molecular structure of (1S)-5,7-anhydro-8-deoxy-1,2 :3,4-di-O-isopropylidene-1-O-methyl-D-glycero-D-galacto-octos-6-ulose has been determined by X-ray analysis. It crystallizes in the tetragonal P4₁(P4₃) space group, with a=b= 10.239(5), c= 16.369(7)Å, Z= 4. The structure was solved by direct methods and refined to an R value of 5.3%. The octose chain is bent in such a way as to keep C-2, -3, -4, and -5 in the same plane. The formation of this compound during the methanolysis of 7,8-dideoxy-7-diazo-1,2 :3,4-di-O-isopropylidene-α-D-galacto-octos-6-ulopyranose(3) by participation of the pyranose ring oxygen atom is discussed in the light of current ideas on diazo-ketone substitution.