Synthesis and characterization of poly‐β‐hydroxybutyrate. II. Synthesis of D ‐poly‐β‐hydroxybutyrate and the mechanism of ring‐opening polymerization of β‐butyrolactone

Synthesis of the naturally occurring polyester, D‐poly‐β‐hydroxybutyrate (PHB) was accomplished by using an optically active monomer. Polymerization of D‐(+)‐β‐butyrolactone (β‐BL) of 73% optical purity with a catalyst system of Et3Al–H2O produced a polymer with a similar optical activity and essentially identical to the natural polymer as isolated from bacterial cells. This paper describes the synthesis and characterization of this optically active polyester along with a suggested mechanism to account for the observed stereospecific polymerization of β‐BL with this catalyst system.