Step B—N-(4-benzyloxycarbonylamino)phenyl)-4-methyl-3-oxo-2-(phenylmethylene)pentanamide (10 mmol), 3-ethyl-5-(2-hydroxyethyl)-4-methylthiazolium bromide (3 mmol), 4-fluorobenzaldehyde (10 mmol) and triethylamine (10 mmol) are heated at reflux in EtOH (150 mL). The progress of the reaction is monitored by tlc. When the reaction is complete, the mixture is cooled and added to water. The aqueous solution is extracted with EtOAc, and the extract is dried and evaporated. The residue is chromatographed to afford the product N-(4-benzyloxycarbonylaminophenyl)-4-methyl-3-oxo-2-[1-phenyl-2-(4-fluorophenyl)-2-oxoethyl]pentanamide 7 (R=4-NHCbz).
