Chemical synthesis of an amylose-like polysaccharide by polymerization of partially benzylated phenyl 1-thio-beta-maltooctaoside derived from gamma-cyclodextrin

An amylose-like alpha-(1,4)-glucan was synthesized by polycondensation and subsequent deprotection of a partially benzylated phenyl 1-thio-beta-maltoo ctaoside having a sole hydroxyl group at the non-reducing end. The key octa saccharide monomer 6 was prepared by means of a single-site acetolytic reac tion of fully acetylated gamma-cyclodextrin and several subsequent chemical manipulations at its reducing and nonreducing ends. On activation with met hyl triflate, the polycondensation of 6 was found to proceed in diethyl eth er through intermolecular glycosidation. The molecular weight of the produc t obtained by preparative GPC on Sephadex LH-60 was 10 000-18 000. Removal of the O-benzyl groups under Birch reaction gave alpha-(1,4)-glucan, the st ereoregularity of which was confirmed by H-1 and C-13 MMR spectroscopy. (C) 1999 Elsevier Science Ltd. All rights reserved.