OXIDATION OF 6,7-DIHYDRO-5H-BENZOCYCLOHEPTENE BY BACTERIAL STRAINS EXPRESSING NAPHTHALENE DIOXYGENASE, BIPHENYL DIOXYGENASE, AND TOLUENE DIOXYGENASE YIELDS HOMOCHIRAL MONOL OR CIS-DIOL ENANTIOMERS AS MAJOR PRODUCTS

Bacterial strains expressing naphthalene, biphenyl, and toluene dioxyg enase were examined for their abilities to oxidize 6,7-dihydro-5H-benz ocycloheptene (benzocyclohept-1-ene). The major oxidation products wer e isolated, and their absolute configurations were determined by chira l H-1 nuclear magnetic resonance analysis of diastereomeric boronate e sters, chiral stationary-phase high-pressure liquid chromatography, an d stereochemical correlation. Pseudomonas sp. strain 9816/11 and Sphin gomonas yanoikuyae (formerly identified as a Beijerinckia sp.) B8/36 e xpressing naphthalene and biphenyl dioxygenases, respectively, oxidize d benzocyclohept-1-ene to a major product identified as (-)-(1R,2S)-ci s-dihydroxybenzocycloheptane (> 98% enantiomeric excess [ee], 50 and 9 0% yield, respectively). In contrast, Pseudomonas putida F39/D express ing toluene dioxygenase oxidized benzocyclohept-1-ene to (+)-(5R)-hydr oxybenzocyclohept-1-ene (> 98% ee, 90% yield) as the major metabolite and to the ''opposite'' diol, (+)-(1S,2R)-cis-dihydroxybenzocyclohepta ne (> 98% ee, 10% yield). The results indicate that, for benzocyclohep t-1-ene, the major reaction catalyzed by naphthalene and biphenyl diox ygenases is dioxygenation whereas toluene dioxygenase catalyzes mainly R-stereospecific benzylic monooxygenation. Although the type of react ion catalyzed by each organism was not predictable, the absolute confi guration of the diol and monol products formed by naphthalene and tolu ene dioxygenases are consistent with the stereochemistry of the produc ts formed by these enzymes from other benzocycloalkene substrates.