Macrocycles. 13. Stannylenated glucose glycosides as cyclic initiators of epsilon-caprolactone and the synthesis of biodegradable networks

The tetraacetates of alpha- and beta-methylglycosides of D-glucose were rea cted with dibutyltin dimethoxide in hot toluene with elimination of methyl acetate. The stannylenated glucose derivatives having a five- and six-membe red tin-containing ring were isolated in a crystalline form. The soluble a- glycoside was used as cyclic initiator for the polymerization of epsilon-ca prolactone at 80 degrees C. It was found by H-1 NMR spectroscopy that the i nsertion of the lactone exclusively occurs into the six-membered ring at th e Sn-O bond of C-6. At prolonged reaction times the stannylenated glucose b egan to degrade at 80 degrees C. However, at short reaction times (t less t han or equal to 2 h) the molecular weight of the macrocyclic polylactone co uld be controlled by the monomer/initiator ratio (M/I). When sebacoyl chlor ide was added at the end of the polymerization, all four Sn-O bonds of the active chain end reacted, and swellable, biodegradable networks were obtain ed. The volume expansion upon swelling depended on the M/I ratio of the rin g-opening polymerization and on the solvent.