合成路线1

The synthesis of tritium-labeled taxol [3''-3H]-taxol has been described: The reaction of baccatin III (I) with chlorotriethylsilane in pyridine gives the protected compound (II), which is condensed with cis-1-benzoyl-4-(3-bromophenyl)-3-(triethylsilyloxy)azetidin-2-one (III) by means of butyllithium in THF, yielding 3''-bromo-2',7-bis-O-(triethylsilyl)taxol (IV). The deprotection of (IV) with pyridine and 48% HF in THF affords 3''-bromotaxol (V), which is finally debrominated with tritium by means of Pd/C and triethylamine in THF. The starting azetidinone (III) is obtained as follows: The condensation of 3-bromobenzaldehyde (VI) with 4-methoxyaniline (VII) in refluxing benzene gives the enamine (VIII), which is cyclized with acetoxyacetyl chloride (IX) by means of triethylamine in dichloromethane, yielding cis-3-acetoxy-4-(3-bromophenyl)-1-(4-methoxyphenyl)azetidin-2-one (X). The reaction of (X) with ceric ammonium nitrate (CAN) in acetonitrile affords cis-3-acetoxy-4-(3-bromophenyl)azetidin-2-one (XI), which is deacetylated with KOH in THF-water giving cis-4-(3-bromophenyl)-3-hydroxyazetidin-2-one (XII). The silylation of (XII) with chlorotriethylsilane in pyridine yields cis-4-(3-bromophenyl)-3-(triethylsilyloxy)azetidin-2-one (XIII), which is finally benzoylated with benzoyl chloride (XIV) and butyllithium in THF to afford the desired azetidinone (III).