Random copolymerizations Of L-lactide with (R)-, (S)-, or rac-1-methyltrimethylene carbonate with bis(pentamethylcyclopentadienyl) samarium-methyl tetrahydrofuranate [(C5Me5)(2)SmMe(THF)] as a novel initiator provided high molecular weight polymers with low polydispersities. Biodegradation of the resulting polymers with tricine and [N-[tris(hydroxymethyl)methyl]-2-aminoethane sulfonic acid (TES) buffers as well as activated sludge showed only a small weight loss, whereas the polymer with proteinase K revealed high biodegradability independent of the optical activity of 1-methyltrimethylene carbonate.