A STEREOSPECIFIC SYNTHESIS OF THE TAXOL SIDE-CHAIN ACETONIDE

The imine 9, prepared by condensation of benzalehyde with benzylamine reacted stereospecifically with 2-acetoxyketene,prepared by 2-acetoxy acetyl chloride and triethylamine in situ to give 3-acetoxy-N-benzyl-4 -phenyl-2-azetidinone(10). The bezylamino group in the molecule 10 was oxidized to benzoyl amide 8 by chromium trioxide in acetic acid solut ion. Ring-openning of 8 with methanol in the presence of potassium car bonate produced taxol side chain methyl ester, methyl benzoyl-2-amino- 3-hydroxy-3-phenyl-propionate(12). In order to esterification of 7-pro tected baccatin III with the taxol side chain, the compound 12 was con verted into acetonide 13, which hydrated to free acid, target molecule taxol side chain acetonide 5 with lithium hydroxide.