合成路线1

A new method for the synthesis of paclitaxel side chain has been developed: The esterification of (S)-phenylglycine (I) with SOCl2 and methanol gives the corresponding methyl ester (II), which is acylated with benzoyl chloride and pyridine to the benzoyl derivative (III). The reduction of (III) with dibutylaluminum hydride (DIBAL) in toluene yields the corresponding aldehyde (IV), which is condensed with 2-(trimethylsilyl)thiazole (V) by means of tetrabutylammonium fluoride (TBAF) to afford the (1R,2S)-N-[2-hydroxy-1-phenyl-2-(2-thiazolyl)ethyl]benzamide (VI) with a 95% enantiomeric purity. The cyclization of (VI) with 2,2-dimethoxypropane (VII) catalyzed by camphosulfonic acid (CSA) gives (4S,5R)-3-benzoyl-2,2-dimethyl-4-phenyl-5-(2-thiazolyl)oxazolidine (VIII), which is treated with methyl trifluoromethanesulfonate to afford (4S,5R)-3-benzoyl-2,2-dimethyl-4-phenyloxazolidine-5-carbaldehyde (IX). Finally, this compound is oxidized with KMnO4 in tert-butanol/aqueous potassium phosphate buffer to yield (4S,5R)-3-benzoyl-2,2-dimethyl-4-phenyloxazolidine-5-carboxylic acid (X), the side chain of paclitaxel suitably protected.