Chiral 1,4-dicarbonyl-2,3- O-isopropylidene derivatives. Rapid racemization on standing

Abstract

1,4-Dicarbonyl-2,3-chiral derivatives are useful synthetic precursors for the preparation of carbocyclic rings but, in many cases, losses of optical purity have been reported. 1- Deoxy-3,4-O- isopropylidene-6-O- trityl- d -erythro- hexo-2,5-diulose and 1- deoxy-3,4-O- isopropylidene-6-O-(tert- butyldiphenylsilyl)- d -erythro- hexo-2,5-diulose were synthesized from d-ribono-1,4-lactone. These compounds were selected to study the epimerizability of 2,3- O-isopropylidene-1,4-dicarbonyl derivatives. It was found that both compounds smoothly epimerize and partially racemize on standing.