Synthesis of 6-deoxymaltooligosaccharides and a study of their lipid-binding properties

Amylose reacted in N,N-dimethylformamide with crystalline bromomethylenedimethylammonium bromide (Vilsmeier bromide) to give 6-bromo-6-deoxyamylose with a high degree of substitution. Reduction of the bromoamylose with sodium borohydride yielded 6-deoxyamylose that, following controlled acetolysis, gave 6-deoxymaltooligosaccharides. Such oligosaccharides, of appropriate chain-length, formed stable complexes with long-chain fatty acids that have a dissociation constant of about 2 microM in their interaction with parinaric acid (trans-9,11,13,15-octadecatetraenoic acid). Treatment of 6-bromoamylose with sodium methoxide in dimethyl sulfoxide produced a 3,6-anhydroamylose that contains few unaltered D-glucose units. This anhydroamylose also bound to a palmitoyl-resin column, suggesting that the polymer may be partially helical and somewhat lipophylic. Finally, reaction of 6-bromoamylose with methylvinyl ether led to the 2,3-di(methoxyethyl) ether that, on reaction with sodium methoxide, gave the 6-methyl ether from which 6-O-methylamylose was obtained by mild acid hydrolysis.