To a solution of acid 101 (0.5 g, 2.1 mmol) in CHCl3 (30 mL) and CH3CN (30 mL) at 0° C. was added oxalyl chloride (1.59 g, 12.6 mmol) and a catalytic amount of DMF. The resulting solution was stirred for 2 h at rt and concentrated in vacuo. The resulting residue was re-dissolved in CHCl3 and cooled to 0° C. To this mixture was added N-methyl-4-isopropyl aniline (0.78 g, 5.2 mmol) and the reaction was stirred overnight warming to rt. The reaction mixture was diluted with CHCl3 (30 mL) and washed with 1 N HCl (50 mL). The combined organic layers were washed with water (75 mL), dried over Na2SO4 and concentrated in vacuo. The product was purified by chromatography on silica gel eluting with EtOAc/hexanes and EtOAc/MeOH to yield 393 as a light yellow solid (0.65 g, 84.4%). mp: 231-233° C. MS (APCI): m/z 370.2 [M+H]+. Anal. Calcd. For C19H23N5O3. 0.1 H2O: C, 61.47; H, 6.30; N, 18.87. Found C, 61.28; H, 6.19; N, 18.57.
