38 生物系によるジケトン類の分子内左右区別とその不斉合成への応用

抄録

The stereochemistry of HLADH-mediated oxidoreduction of C_1-ketones was governed by the same "quadrant rule" observed in the microbial reduction which states that hydrogen attack from the lower quadrants is most favored for the C_1-1 quadrant orientation. Two completely opposite stereospecificities toward C_2-ketones which were found in the microbial reduction and HLADH-catalyzed oxidoreduction have led us to propose the microbial P-C_2-ketone rule and the HLADH M-C_2-ketone rule. An extension of these studies has prompted us to examine the stereochemistry of the metabolites of the "meso diketones". The microbial reduction of 1,10-dioxo[2.2]metacyclophane (9) presented the first established example of the enantiotopic selectivity with respect to the plane of prochirality. HLADH-mediated reduction differentiated between the enantiotopic carbonyl groups in cis-decalin-2,7-dione (14) and its 10-methyl derivative 15 to provide (-)-(7S,9S,10R)-cis,cis-ketols 16 and 17 respectively by the re-face attack of hydrogen on the pro-R carbonyl group in the substrates. On the other hand, the microbial reduction showed an opposite selectivity to provide (-)-(7S,9R,10S)-cis,trans-ketols 18 and 19 respectively by the re-face attack of hydrogen on the pro-S carbonyl group. Both (-)-ketols 16 and 17 were converted via (+)-22 and 23 into respective (+)-twistane (24) and (+)-1-methyltwistane (25) of high optical purity.