合成路线1

A new synthesis of [14C]-labeled paclitaxel has been published: The protection of L-threonine methyl ester (I) with tert-butoxydiphenylchlorosilane (BPS-Cl) gives the compound (II), which is condensed with [14C]-labeled benzaldehyde (III), yielding the imine (IV). The cyclization of (IV) with acetoxyacetyl chloride (V) by means of triethylamine affords the azetidinone (VI), which is deprotected with tetrabutylammonium fluoride to the hydroxy ester (VII). The dehydration of (VII) with p-toluenesulfonyl chloride and triethylamine affords the unsaturated ester (VIII), which by ozonolysis is converted to the oxalimide (IX). Elimination of the oxalyl group with hydrazine gives the labeled azetidinone (X), which is deacetylated to the hydroxyazetidinone (XI) and protected with triethylchlorosilane (TES-Cl) to (XII). The benzoylation of (XII) with benzoyl chloride (XIII) and dimethylaminopyridine (DMAP) yields the corresponding benzoylated compound (XIV), which is then condensed with triethylsilyl-baccatin III (XV) by means of butyllithium to afford silylated labeled paclitaxel (XVI). Finally, this compound is deprotected with HCl. The intermediate silylated baccatin III (XV) is obtained from paclitaxel (XVII) by hydrogenolysis with NaBH4 to baccatin III (XVIII) and silylation with triethylsilyl chloride to (XV).