合成路线1

A new synthesis of paclitaxel has been reported: The esterification of (2R,3S)-2,3-epoxy-3-phenylpropionic acid (I) with 2-(trimethylsilyl)ethanol (II) by means of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in hot toluene gives the expected ester (III), which is treated with LiBr in acetic acid to yield the (2R,3R)-3-bromo-2-hydroxy ester (IV). The reaction of (IV) with sodium azide in hot DMF affords the corresponding azido derivative (V), which is reduced with ammonium formate or H2 over Pd/C giving the (2R,3S)-3-amino-2-hydroxy ester (VI). The amidation of (VI) with benzyl chloroformate (VII) yields the corresponding benzyloxycarbonylamino compound (VIII), which is esterified with benzoyl chloride (IX) and triethylamine affording (2R,3S)-2-(benzoyloxy)-3-(benzyloxycarbonylamino)-3-phenylpropionic acid 2-(trimethylsilyl)ethyl ester (X). The condensation of the ester (X) with 7-O-(triethylsilyl)baccatin (XI) by means of 4-(1-pyrrolidinyl)-piperidine (4-PP) and dicyclohexylcarbodiimide (DCC) in hot toluene gives the mixed ester (XII). Finally, this compound is hydrogenated with ammonium formate and Pd/C to obtain a free amino group to which the benzoyl group of the a-position is transferred by a treatment with formic acid yielding pure paclitaxel.