Selective Substitution of Hydroxyl Groups in Sucrose

Abstract

In studying the fundamental chemistry of sucrose over the past two decades, we have discovered a profile of chemical reactivity that is unique to sucrose and devised procedures for the isolation and characterisation of the products. Thus precise control of the reactions of sucrose with sulphuryl chloride in pyridine can effect replacement of two, three or four hydroxyl groups in sucrose. By variation of the reaction conditions we can isolate 6,6′-dichloro-6,6′-dideoxysucrose, or 4,6,6′-trichloro-4,6,6′-trideoxy-galacto-sucrose in good yield, each crystalline or as a crystalline derivative, directly from the reaction without using chromatographic columns for isolation. Likewise, sulphonate esters of sucrose can be made directly, such as 1′,6,6′-tri-O-mesitylenesulphonyl-sucrose. We have studied the conversion of chlorosucroses into potentially useful products. Thus the di- and trichloro compounds are readily converted into 3,6:3′,6′-dianhydrosucrose and its 4-chloro derivative respectively. Furthermore, reductive dehalogenation of 113C chemical shifts in ppm downfield from T.M.S 2 the chlorosucroses with hydrogen-Raney nickel in the presence of base, afforded di-, tri- and tetradeoxysucroses in high yield. Studies on the application of 13C n.m.r.to sucrose and its derivatives have shown that it is a valuable tool for characterisation.