Further examples of orthoesterification under kinetically controlled conditions. Application to the selective acylation of sucrose, maltose and alpha,alpha-trehalose.

Orthoesterification of sucrose with 1,1-dimethoxyethene under kinetic control gave 4,6-O-methoxyethylidenesucrose in 77% crude yield. Similar orthoesterification of maltose led essentially after acetylation to 1,2,3,6,2',3'-hexa-O-acetyl-4'-6'-O-methoxyethylidenemaltose. Analogous treatment of alpha, alpha-trehalose gave 2,3,2',3'-tetra-O-acetyl-4,6:4',6'-di-O-methoxyethylidene-alpha, alpha-trehalose in 47% yield. The acid-catalyzed opening of these orthoesters was studied, and these reactions were shown to give disaccharides selectively protected by acetyl groups.