Anthracyclines. XII. The preparation of (—)-(7 <i>R</i> )-7-Acetyl-7-(t-butyldimethylsilyoxy-1(4 <i>H</i> )-one and (+)-(6 <i>R</i> )-6-Acetyl-6-(t-butyldimethylsilyloxy)- 4,4-dimethoxy-5,6,7,8-tetrahydronaphthalene-1(4 <i>H</i> )-one: an Improved Route to Chiral AB Synthons for 7-Deoxydaunomycinone

Abstract

The title dienones (2) and (5) were prepared from the chiral alcohols (7a) and (7b) respectively. These key starting materials were in turn available from the reduction of 3-acetyl-5-benzyloxy-8-methoxy-1,2- dihydronaphthalene (6a) and 3-acetyl-8-benzyloxy-5-methoxy-1,2- dihydronaphthalene (6b) with lithium aluminium hydride modified with (—)-N- methylephedrine and N- ethylaniline . Chiral phase high-pressure liquid chromatography was used to analyse the enantioselectivity of these reductions which were shown to yield variable results depending upon the origin of the reducing agent.