AMINO-ACID OLIGOMER MICROSPHERES AS DRUG-DELIVERY SYSTEMS .2. OLIGOMERIZATION OF NCAS INITIATED WITH L-TYROSINE METHYL-ESTER

Oligomerizations of various amino acid N-carboxyanhydrides (NCAs) were prepared in the presence of L-tyrosine methyl ester (Tyr.Me). Tyr.Me was found to be an efficient initiator to form oligopeptides consistin g of L-aspartic acid, L-glutamic acid, L-phenylalanine, and L-tyrosine with random arrangements of amino acids. In acidic solution, the olig opeptides formed microspheres which were capable of encapsulating macr omolecular drugs such as insulin and heparin. These microspheres were considered to be potential oral drug delivery systems.