Stereochemistry of the Baeyer-Villiger-type conversion of 4-(4-hydroxyphenyl)butan-2-one (raspberry ketone) into tyrosol mediated by Beauveria bassiana

Feeding experiments in Beauveria bassiana (ATCC 7159) of (2R,3S)-[2,3-H-2(2)]-4-(4-hydroxyphenyl)-butan-2-ol (15) and (2R,3R)-[1,3-H-2(4)]-(4-hydroxyphenyl)-butan-2-ol (16) afford (1S)- and (IR)-[1-H-2]tyrosol (17) and (18), respectively, as indicated by NMR studies on the (+)-MTPA esters 21 and 23 and comparison with an authentic sample of the (S) enantiomer. These results indicate that the C-2, Baeyer-Villiger-type, chain shortening of the C-6-C-4 framework of the intermediate raspberry ketone 1 to give the C-6-C-2 tyrosol (4) occurs with retention of configuration. The asymmetrically labeled substrates 15 and 16 have been obtained by enzymic resolution of derivatives of (2SR,3RS)-6 and (2SR,3SR)-12, prepared, in turn, by syn catalytic reduction with deuterium and with hydrogen gas, respectively, of the (Z) enol acetates 5 and 11.