SYNTHESES OF ANGUCYCLINONES RELATED TO OCHROMYCINONE - II - REGIOSELECTIVE AND STEREOSELECTIVE REDUCTION OF A TETRAHYDROANGUCYCLINONE

The reduction of racemic thoxy-3,3-dimethyl-3,4,5,6,6a,12a-hexahydrobe nz[a] anthracene-reduction of racemic 8-hydroxy-6-methoxy-3,3-dimethyl -3,4 5 1,7,12(2H)-trione, with either (i) sodium borohydride and ceriu m(III) chloride in ethanol (the Luche reagent) or (ii) sodium borohydr ide in ethanol, was shown (by n.m.r. and X-ray crystallographic data) to yield the same racemic product, viz. y-3,3-dimethyl-2,3,4,5,6,6a,7, 12a-octahydrobenz[a] anthracene-l, 12-dione. The 7-OH and 6-OMe groups are cis to each other. The observed regiochemistry can be rationalize d in both cases by preferential interaction of respectively (i) the ce rium(III) chloride of the Luche reagent, and (ii) sodium borohydride w ith the 8-OH group of (3) (the 8-OH group is more acidic than the solv ent), while the cis stereochemistry is consistent with hydride deliver y from the less hindered face in (3).