A stereoselective synthesis of sucrose via redox glycosidation and investigations in the use of organoantimony reagents in organic synthesis.

摘要

The efficient stereoselective synthesis of glycosides has eluded synthetic organic chemists for decades. Redox glycosidation offers great potential for achieving this goal. An esterification reaction rather than the traditional etherification reaction allows excellent control in the formation of the key anomeric center. Reductive unravelling affords the carbohydrate skeleton of the second monosaccharide unit. The synthetic utility of this methodology is demonstrated in the stereoselective synthesis of sucrose.; In the course of our studies of redox glycosidation it became necessary to convert a neopentyl iodide to the corresponding alcohol. Radical chemistry proved to be the method of choice in affecting this difficult transformation. Further investigations of radical reactions led to the discovery of tetraphenyl distibine as an intriguing radical source. The scope and reactivity of this antimony reagent was examined. When (tetrahydropyranyl)methyl iodide was treated with tetraphenyl distibine the air-stable pyranosyl diphenyl stibine was formed. Oxidation with basic peroxide afforded (tetrahydropyranyl)methyl alcohol. In marked contrast, treatment of (tetrahydrofurfuryl)methyl iodide with tetraphenyl distibine only reluctantly afforded the extremely air-sensitive furanosyl diphenyl stibine. Air oxidation gave tetrahydrofurfuryl alcohol. The chemoselective nature of this reagent lends itself to future study.