| Abstract
| - Novozym 435-catalyzed ring-opening of a range of ω-methylated lactones demonstratesfascinating differences in rate of reaction and enantioselectivity. A switch from S- to R-selectivity wasobserved upon going from small (ring sizes ≤7) to large lactones (ring sizes ≥8). This was attributed tothe transition from a cisoid to a transoid conformational preference of the ester bond on going from smallto large lactones. The S-selectivity of the ring-opening of the small, cisoid lactones was low to moderate,while the R-selectivity of the ring-opening of the large transoid lactones was surprisingly high. TheS-selectivity of the ring-opening of the small, cisoid lactones combined with the established R-selectivity ofthe transesterification of (aliphatic) secondary alcohols prevented polymerization from taking place. Ring-opening of the large, transoid lactones was R-selective with high enantioselectivity. As a result, these lactonescould be polymerized, without exception, by straightforward kinetic resolution polymerization, yielding theenantiopure R-polyester with excellent enantiomeric excess (>99%).
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