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