Bacterial biotransformation of isoprene and related dienes

The bacterium Pseudomonas putida ML 2 was used in the oxidative biodegradat ion of the acyclic dienes isoprene, trans-piperylene, cis-piperylene, and 1 ,3-butadiene. Regioselective dioxygenase-catalyzed dihydroxylation of alken es yielded vicinal diols in the preferred sequence monosubstituted > cis-di substituted > gem-disubstituted > trans-disubstituted. The isolated diol me tabolites had an excess of the R configuration (9-97% ee), and further diol oxidation was controlled by addition of propylene glycol as an inhibitor. Stereoselectivity using the ML2 strain resulted from both enzymatic asymmet ric alkene dihydroxylation and kinetic resolution of diols. Enantioselectiv e oxidation of the allylic secondary alcohol group of R configuration yield ed the corresponding unsaturated ketoalcohol; the residual diol was recover ed with a large excess (greater than or equal to 93% ee) of the S configura tion. In addition to the enzymatic diene oxidation steps yielding unsaturat ed diols and ketoalcohols, evidence was also found of enzymatic alkene hydr ogenation to yield saturated ketoalcohols and diols.