Further examples of orthoesterification under kinetically controlled conditions application to the selective acylation of sucrose, maltose and α,α-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 α,α-trehalose gave 2,3,2′,3′-tetra-O-acetyl-4,6:4′,6′-di-O-methoxyethylidene-α,α-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.