Regioselectivity of the microbial hydroxylation of nortricyclanol and its derivatives

While biotransformations of nortricyclanol did not give detectable products , microbial hydroxylation could be achieved by using its benzoate ester or its phenylcarbamate. Here eight fungi were found to hydroxylate these subst rates in moderate yield. All strains formed optically active exo, endo-5-hy droxy-nortricyclanol-3 -benzoate or -phenylcarbamate as the main product. R hizopus arrhizus ATCC 11145 and Mortierella isabellina DSM 63355 were the b est strains. Only the fermentation of the benzoate gave additional products , namely the corresponding endo, exo- and exo, endo-isomers in low yield. T he structures of the metabolites were elucidated spectroscopically, particu larly by using various NMR techniques. The hydroxylated nortricyclanol este rs are compounds which are difficult to produce chemically. The presence of the ester function makes them chiral compounds and the biotransfonnations were found to be enantioselective. Therefore, microbial oxidation of these nortricyclanol esters is a valuable tool to produce chiral hydroxylated nor tricyclanol derivatives which can serve as intermediates in syntheses.