合成路线1

A new partial synthesis for taxol has been reported: The cyclization of N-(4-methoxyphenyl)benzylideneimine (I) with acetoxyacetyl chloride (II) by means of triethylamine in dichloromethane gives cis-3-acetoxy-1-(4-methoxyphenyl)-4-phenylazetidin-2-one (III), which is treated with ceric ammonium nitrate in acetonitrile to afford cis-3-acetoxy-4-phenylazetidin-2-one (IV). Hydrolysis of (IV) with KOH in THF-water yields cis-3-hydroxy-4-phenylazetidin-2-one (V), which is submitted to optical resolution giving the (3R,4S)-isomer (VI). The reaction of (VI) with ethyl vinyl ether (VII) by means of methanesulfonic acid in THF affords (3R,4S)-3-(1-ethoxyethoxy)-4-phenylazetidin-2-one (VIII), which is benzoylated with benzoyl chloride (IX) and butyllithium in hexane to give (X). Opening of the azetidine ring of (X) with KOH in THF-water gives (2R,3S)-3-(benzamido)-2-(1-ethoxyethoxy)propanoic acid (XI), which is cyclized with potassium tert-butoxide and methanesulfonyl chloride to (4S,5R)-5-(1-ethoxyethoxy)-2,4-diphenyl-5,6-dihydro-4H-1,3-oxazin-6-one (XII). Finally, this compound is condensed with 7-O-(triethylsilyl)baccatin III (XIV) [prepared from 10-deacetylbaccatin III (XIII) by successive reaction with triethylsilyl chloride and acetyl chloride] by means of dimethylaminopyridine (DMAP) in pyridine.