Enantioselective Reduction of Some Aromatic Ketones by Baker\u27s Yeast

The reduction of aromatic ketones 1- 6 by baker\u27s yeast showed that acceptability of the substrates is not governed either by the number of aryl groups at by the distance of the carbonyl group from the aryl moiety. Relative rates of conversion of 3, 4, and 6 vs. ethyl acetoacetate as the "standard" substrate were reproducible in the order 3>6>4. Strong inhibition of reduction of ethyl acetoacetate by benzene vanished at very law concentrations of both. Reduction of phenyl-pyrid- 2\u27yl-methyl ketone (1) and its deazaanalogue (6) gave the chiral sec. alcohols of the opposite configuration. (-) -7 and (+) -12, respectively. This could be ascribed to the prevalent binding of enol lA by the opposite enantioface, as compared lo 6. Absolute configuratian of ( - ) -7 is tentatively assigned as R by the empirical rule based on the lNMR spectra of Mosher\u27s acid esters 13-15. This assignment is confirmed by the single crystal X-ray structure determination of camphanic acid ester 16A, which on hydrolysis affards (-) - 7