The reaction of 2-hydroxyglycal esters with alcohols in the presence of N-iodosuccinimide, stereoselective synthesis of α anomers of alkyl 3-deoxyhex-2-enopyranosides and 3,4-dideoxyhex-3-enopyranosid-2-uloses

✍ Scribed by Oscar Varela; Griselda M. de Fina; Rosa M. de Lederkremer

• Publisher: Elsevier Science
• Year: 1987
• Tongue: English
• Weight: 681 KB
• Volume: 167
• Category: Article
• ISSN: 0008-6215
• DOI: 10.1016/0008-6215(87)80278-1

✦ Synopsis

Reaction of 2,3,4,6-tetra-O-acetyl-1,5-anhydro-o-arubino-hex-l-enitol

(1; 2hydroxyglucal tetraacetate) with 1.0-1.5 mol of primary, secondary, or tertiary alcohols, in the presence of 0.1-1.0 mol of N-iodosuccinimide (NIS) in acetonitrjle as solvent, afforded the a anomers of alkyl 3-deoxyhex-2-enopyranosides in very good yields. The reaction proceeded more slowly, and with poorer yields, in the case of the tetrabenzoate corresponding to 1. When 1 was treated with higher concentrations of 2-propanol, increasing proportions of a reaction by-product, 2-propyl 6-0-acetyl-3,4-dideoxy-a-D-glycero-hex-3-enopyranosid-2-ulose (1% were produced. Such sugar enones as 10 were more readily formed when the starting 2-hydroxyglycal acetate had the 1~x0 configuration. Thus, two cholesteryl a-hex3enopyranosid-Zulose derivatives were each prepared in one step and with good yields. Remarkable stereoselectivity for the formation of the (Y anomers was observed in all of these reactions.