Cis-(-)-menthyl phenylglycidates in the asymmetric synthesis of taxol side chain

Abstract

The one-pot azidation and benzoylation of a mixture of cis (-)-menthyl phenylglycidates provide quantitatively the corresponding (2R,3S)-, and (2S,3R)-3-azido-1-((1R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy)-1-oxo-3-phenylpropan-2-yl benzoate. Enantiopure (2R,3S)-3-azido-1((1R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy)-1-oxo-3-phenylpropan-2-yl benzoate crystallize from MeOH at room temperature in high yields. The reduction of the latter with Zn-TMSCl produces (-)-menthyl 3-benzamido-3-phenyl-2-(trimethylsilyloxy) propanoate which upon simultanious desilylation and hydrolysis provide the taxol side chain N-benzoyl-(2R, 3S)-3-phenylisoserine.