A NOVEL-APPROACH TO THE SYNTHESIS OF TAXOL - A SYNTHESIS OF OPTICALLY-ACTIVE 3,7-DIBENZYLOXY-4,8-DI-T-BUTYL-DIMETHYLSILOXY-5,5-DIMETHYL-6-P-METHOXYBENZYLOXY-2-OCTANONE BY WAY OF STEREOSELECTIVE ALDOL REACTIONS

Optically active 3,7-dibenzyloxy-4,8-di-t-butyldimethylsiloxy- 5,5-dimethyl-6-p-methoxybenzyloxy-2-octanone (2) has been synthesized by way of diastereoselective aldol reaction between 4-benzyloxy-5-t-butyldimethylsiloxy-2,2-dimethyl-3-p-methoxy- benzyloxypentanal (3) and ketene silyl acetal 4 using MgBr(2)OEt(2) as a catalyst. The chiral pentanal 3 was synthesized either by asymmetric aldol reaction of both prochiral aldehyde 5 and ketene silyl acetal 4 using a chiral Lewis acid or by diastereoselective aldol reaction between the chiral aldehyde 6 derived from L-serine and the lithium enolate derived from methyl isobutyrate.