Acylation of starch with vinyl acetate in water

Acetylation of different types of starch with vinyl acetate in water in the presence of a base is described. Maximum degree of substitution under these conditions is 1.1. Vinyl esters of higher homologous acids (vinyl laurate) react very slowly giving very low degrees of substitution after long reaction times. The reaction mixture is biphasic, because vinyl esters are not miscible with water. Formation of two layers reduces loss of acylating agent due to reaction with water - which is a major problem encountered for esterification with acid anhydrides or chlorides - to less than 5%. Unlike acylation of starch in DMSO with vinyl esters, the acetates of starch obtained by the method reported do not show regioselective distribution of acetyl groups within the anhydroglucose units.