Sequential polypeptides. Part IV. The synthesis of poly-(L-alanyl-giycyi-L-proline) and its stereoisomers

Abstract

Several alternative routes to sequential polypeptides containing repeating glycyl-L-prolyl-L-alanyl sequences have been examined. The most satisfactory involved treatment of L-alanylglycyl-L-proline pentachlorophenyl ester hydrobromide with tertiary base in dimethyl sulphoxide: polydisperse poly-(L-alanylglycyl-L-proline) was obtained, after dialysis, in 50–70% yield (number and weight average molecular weight ca. 9000 and ca. 12,000–14,000, respectively). Analogous routes were employed for the synthesis of polydisperse preparations of poly-(D-alanylglycyl-D-proline), poly-(D-alanylglycyl-L-proline), and poly-(L-alanylglycyl-D-proline): the D–Land L–D polymers were obtained in lower yield and were of lower molecular weight than were the L–L and D–D polymers.