The Wittig Reaction in Carbohydrate Chemistry

Abstract

The Wittig reaction is considered one of the fundamental synthetic methods of modern organic chemistry. It is the most convenient route to unsaturated compounds. The remarkable features of this reaction include mild reaction conditions, high quantitative yields, and the absence of migration of the bond formed. A number of natural compounds such as carotenoids and methylenic steroids are synthesized by using this reaction. This chapter summarizes the advances in the application of the Wittig reaction in the carbohydrate field. The Wittig reaction involves the interaction of an oxo compound with phosphonium ylides, through an intermediate betaine to yield the appropriate alkene and triphenylphosphine oxide. The Wittig reaction generally results in the preponderant formation of the trans-isomer. The yield of the cis-isomer is increased with decrease in stability of the phosphorane. It is noted that the application of the Wittig reaction in the carbohydrate field is accompanied by certain difficulties. A correct choice of the initial sugar components is the main problem, owing to the basicity of phosphoranes.