Enzymatic resolution of sterically demanding bicyclo[3.2.0]heptanes: evidence for a novel hydrolase in crude porcine pancreatic lipase and the advantages of using organic media for some of the biotransformations

Sterically demanding 7,7-dimethylbicyclo[3.2.0]hept-2-en-6-one 1 was enzymatically resolved via the exo-acetate 11a using crude porcine pancreatic lipase. By employing different fractions of hydrolases from the crude enzyme, evidence was obtained that an enzymatic ‘impurity’ was responsible for the highly selective reaction (E > 300). Alternatively, 7,7-dimethyl and 7,7-diphenyl derivatives 1 and 2 were equally well resolved, via bromohydrins 12b and 13b, by lipases from Pseudomonas cepacia and Candida cylindracea but only when acylations were conducted in organic media.