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New and efficient approaches to the semisynthesis of taxol and its C-13 side chain analogs by means of β-lactam synthon method

Highly efficient chiral ester enolate-imine condensation giving 3-hydroxy-4-aryl-β -lactams with excellent enantiomeric purity is successfully applied to the asymmetric synthesis of the enantiomerically pure taxol C-13 side chain, N-benzoyl-(2R, 3S)-3- phenyl-isoserine and its analogs. (3R, 4S)-N-benzoyl- 3-(1-ethoxyethoxy)-4-phenyl-2- azetidinone readily derived from the 3-hydroxy-4-phenyl-β -lactam is coupled with protected baccatin IIIs, followed by deprotection to give optically pure taxol and 10- deacetyl-7, 10-bis(Troc)-taxol in good yields. Fully assigned 1H, 13C, and 2D (COSY and HETCOR) NMR spectra of taxol thus synthesized are shown and discussed.

chiral ester ; enolate-imine ; taxol

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