Regioselective end-functionalization of polylactide oligomers with D-glucose and D-galactose

D-glucose and D-galactose end-functionalized polylactide oligomers were synthesized by controlled ring-opening polymerization of lactide using aluminium triisopropoxide, triethyl-aluminium or stannous octoate as promoter. Accordingly, two selectively protected monosaccharides were studied as co-initiators, either 1,2;5,6-di-O-isopropylidene-α-D-glucofuranose (1) and 1,2;3,4-di-O-isopropylidene-α-D-galactopyranose (2). In contrast to what is known in polymerization of ε-caprolactone, both protected monosaccharides proved to be efficient co-initiators and yielded end-functionalized polylactide chains with controlled regioselectivity (C-3 or C-6 linkage), predictable molecular weights and narrow molecular weight distributions.