| Abstract: | Unnatural‐type syndiotactic and atactic poly(R,S)‐3‐hydroxybutanoate]s P(3HB)s] were enzymatically transformed into a reactive cyclic 3HB oligomer of molecular weight ca. 500 in an organic solvent, such as toluene, using immobilized lipase from Candida antarctica at 40°C for 24 h. It was confirmed that similar results were obtained for both syndiotactic and atactic P(3HB)s. On the other hand, the acidic degradation of these polymers using a protonic acid, such as p‐toluenesulfonic acid, exclusively produced the linear 3HB oligomer instead of the cyclic oligomer. The formation of the cyclic oligomer was regarded as the characteristic feature of the lipase‐catalyzed degradation in organic media. The cyclic oligomer obtained readily reacted with alcohol as a nucleophile, and using lipase, to produce the alkyl ester of the 3HB oligomer. |
