Polyesters prepared by polycondensation in the presence of carbodiimides, 2. On the reaction of methyl α‐(S)‐malate with N,N′‐dicyclohexylcarbodiimide under mild conditions

The reaction of methyl α‐(S)‐malate with N,N′‐dicyclohexylcarbodiimide in the presence of amines under mild conditions was studied. It was established that in solvents with weak donor properties, N‐acyl derivatives are preferentially formed instead of ester condensation products. An optically active polymer fraction was separated by precipitation in diethyl ether (yield up to 30%) with M̄n,GPC 1 000 to 4 000 and of low polydispersity M̄w/M̄n = 1,1–1,4. The method permits the preparation of optically active biodegradable condensation products with controlled molecular structure.