Sucrochemistry

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.

Tin(IV)-functionalised polymer supports; non-toxic and practical reagents for regioselective acetylation of sucrose

Polymer-supported butyltin(IV) reagents have been surveyed for regioselectivity in acetylation of sucrose. Polymer-supported butyltin(IV) dichloride 8 catalysed the acetylation of sucrose to give a 59% yield of 6-O-acetyl sucrose 3, the precursor of sucralose. The yield is close to that of a previously reported process involving dibutyltin(IV) oxide (Bu2SnO). The spent polymeric resin could readily be regenerated and can be subsequently used in further synthetic reactions.

Regioselective enzymic deacetylation of octa-O-acetylsucrose: preparation of hepta-O-acetylsucroses

Deacetylation of octa-O-acetylsucrose (1) with Alcalase or protease N gave the 2,3,4,6,3',4',6'-hepta-acetate (2) as the initial major product with the 2,3,4,6,3',4'-hexa-acetate (3) as the subsequent main product. The 2,3,4,1',3',4',6'-hepta-acetate (5) was obtained from 1 by the action of lipase OF or lipase AP6, and the 2,3,4,6,1',3',6'-(4) and 2,3,4,6,1',3',4'-hepta-acetate (7) by the action of Candida lipase and chymotrypsin, respectively. The 2,3,6,1',3',4',6'-hepta-acetate (6) was formed from 5 by acyl migration.