SYNTHESIS AND PROOF OF STEREOSTRUCTURE OF A NEW (-ISOMENTHONE-DERIVEDHOMOCHIRAL 1,3-DIOL())

Diastereopure (+)-isomenthone-derived ketoalcohol 2 was converted to t he homochiral 1,3-diol 6 either by direct reduction or reduction of si lyl protected derivatives. The diastereomeric preference of the reduct ion was the same in all cases. Reduction of 2 with NaBH4 gave essentia lly a single diastereomer, while reduction with LiAlH4 gave similar to 6:1 selectivity in favour of the same diastereomer. Reduction of the silyl protected substrates 7 and 8 gave, after column chromatography, 98% yield of a single diastereomer, desilylation of which established this to be the same; diastereomer as obtained through hydride reductio ns of unprotected 2. The structure of diol 6 was proven through coupli ng data and NOE experiments at 600 MHz. Overall, two stereochemistry i ntroducing steps have elaborated the two stereogenic centres of (+)-is omenthone to the five contiguous stereogenic centres of 6. (C) 1998 El sevier Science Ltd. All rights reserved.