The partial hydrolysis of perhydropyrrolizine-3,5-dione (I) in the presence of benzyl alcohol (II) by means of aqueous concentrated HCl at 98 C gives benzyl 5-oxopyrrolidine-2-propenoate (III), which is condensed with 4-methoxybenzoyl chloride (IV) by means of triethylamine in hot THF to afford benzyl 1-(4-methoxybenzoyl)-5-oxopyrrolidine-3-propanoate (V). Finally, this compound ls debenzylated by hydrogenolysis with H2 over Pd/C in THF.
The esterification of bromoacetic acid (I) with benzyl alcohol (II) gives the corresponding ester (III), which by reaction with triphenylphosphine (IV) in hot toluene yields the phosphonium bromide (V). The reaction of (V) with NaOH in water-dichloromethane affords benzyl(triphenylphosphoranylidene) acetate (VI), which is submitted to a Wittig condensation with 5-(hydroxymethyl)-2-pyrrolidone (VII) in the presence of Dess-Martin periodinane (DMPI) giving benzyl 3-(5-oxo-2-pyrrolidinyl)-2(E) propenoate (VIII). The acylation of (VIII) with 4-methoxybenzoyl chloride (IX) by means of triethylamine in hot toluene yields the corresponding amide (X), which is finally hydrogenated and deprotected with H2 over Pd/C in THF.