CATIONIC RING-OPENING POLYMERIZATION OF 4,5-DIHYDRO-1,3-OXAZOL-5-ONESTO PRODUCE N-ALKOXYCARBONYLATED POLYPEPTIDES AND ITS RELATED OLIGOMERIZATION

The present paper describes the cationic ring-opening polymerization o f 2-alkoxy-4,5-dihydro-1,3-oxazol-5-ones derived from L-valine. L-isol eucine, L-leucine with methyl trifluoromethanesulfonate (MeOTf) as the initiator. The polymerization of these oxazolones proceeded successfu lly below 0 degrees C and gave poly(N-alkoxycarbonyl-alpha-amino acid) s in moderate yields. The ease of polymerization was dependent on the 2- and 4-substituents of the oxazolone ring and the combination of bul ky groups strongly reduces it. The reaction of 2-ethoxy-4,4-dimethyl-4 ,5-dihydro-1,3-oxazol-5-one with a catalytic amount of MeOTf did not p roduce a polymer, but yielded a bicyclic dimer, selectively.