To a stirred solution of 1-(2-fluoro-4-iodophenyl)-3-(4-methoxybenzyl)-6,8-dimethyl-2,4,7-trioxo-1,2,3,4,7,8-hexahydropyrido[2,3-d]pyrimidin-5-yl 4-methylbenzene sulfonate (2a) (2.0 gm, 2.79 mmol) in DMA (5 ml) was added 2,6-lutidine (0.98 ml, 8.36 mmol) and 3-aminobenzoic acid (1.147 gm, 8.36 mmol). The reaction mixture was heated at 130° C. for 16 h. The reaction mixture was cooled to room temperature and water was added followed by extraction with Ethyl acetate. The organic phase was dried over sodium sulphate. The solvent was evaporated in vacuo and the residual solid was purified by silica gel column chromatography, eluting with Hexane:Ethyl acetate (1:1), to yield the titled compound (2b) (1.4 g)
