Stereospecific enzymatic hydrolysis of racemic epoxide: a process for making chiral epoxide

Among various microbial cultures evaluated, Rhodotorula glutinis SC 16293 a nd Aspergillus niger SC 16311 catalyzed the stereospecific hydrolysis of th e racemic epoxide, RS-1-{2',3'-dihydrobenzo[b]furan-4'-yl}-1,2-oxirane, 1 t o the corresponding R-diol, R-1-{2',3'-dihydrobenzo[b]furan-4'-yl}-ethane-1 ,2-diol, 3. The S-epoxide, S-1-{2',3'-dihydrobenzo[b]furan-4'-yl}-1,2 remai ned unreacted in the reaction mixture. A reaction yield of 45-50% (theoreti cal maximum yield is 50%) and an enantiomeric excess (ee) of >95% were obta ined for unreacted S-epoxide 2 using each culture. Addition of 10% methyl t ert-butyl ether to an aqueous reaction mixture during hydrolysis by R. glut inis improved the ee of the unreacted S-epoxide 2 to >99% (yield 48%) and t hat of the R-diol 3 to 79%. Unlike R. glutinis, hydrolysis of racemic epoxi de 1 in the presence of 10% methyl tert-butyl ether by A. niger showed an a dverse effect and gave S-epoxide 2 in 54% yield and 49% ee. (C) 1999 Elsevi er Science Ltd. All rights reserved.