合成路线1

The diazonium salt prepared from 3,4-methylenedioxyaniline (I) was coupled to methyl acrylate (II) in the presence of Cu2O and HBr to produce the 2-bromo-3-phenylpropionic ester (III). Subsequent displacement of the bromo group of (III) by alpha-mercaptopropionic acid (IV) gave sulfide (V). After conversion of (V) to the corresponding acid chloride with (COCl)2, intramolecular Friedel-Crafts cyclization in the presence of SnCl4 afforded the benzothiepinone (VI) as a mixture of cis and trans isomers. Further treatment of this mixture with sodium methoxide equilibrated the mixture to the more stable trans form (VII). Resolution of the racemic trans ester was achieved by basic hydrolysis, coupling to ethyl (R)-(-)-mandelate (VIII), and fractional crystallization of the desired diastereomer (IX) from EtOAc-hexane. Ester hydrolysis of (IX) under acidic conditions led to the chiral carboxylic acid (X), which was finally condensed with diethyl 4-aminobenzylphosphonate (XI) to furnish the title compound.