To generate the acid chloride: to a chilled suspension of 3-methylisoxazole-4-carboxylic acid (231 mg, 1.8 mmol) in dry CH2Cl2 (3.0 mL) was added oxalyl chloride (0.31 mL, 3.7 mmol) followed by DMF (1 drop). The suspension was stirred at 0° C. for 5 minutes and then at room temperature for 1 hour. The resulting solution was concentrated in vacuo at ambient temperature to yield an oil, dried by stirring under nitrogen. 10a-(4-chlorophenyl)-7-(pyridin-2-yl)-2,3,10,10a-tetrahydro-1H,5H-imidazo[1,2-a]pyrazolo[1,5-d]pyrazin-5-one (111 mg, 0.3 mmol) in pyridine (3.5 mL) was added to a mixture of the acid chloride (generated as above, 1.8 mmol) in pyridine (2 mL) at 0° C. and stirred at 0° C. to room temperature for 1 hour. LCMS after this time indicated the reaction was complete. The suspension was then diluted with water (15 mL) and extracted with CH2Cl2 (3×10 mL). The extracts were combined, dried (Na2SO4), filtered and concentrated in vacuo to yield a yellow residue. The material was purified by trituration with EtOAc/hexanes (9:1) to give 10a-(4-chlorophenyl)-1-[(3-methyl-1,2-oxazol-4-yl)carbonyl]-7-(pyridin-2-yl)-2,3,10,10a-tetrahydro-1H,5H-imidazo[1,2-a]pyrazolo[1,5-d]pyrazin-5-one (63) as a beige solid (70 mg, yield 49%).
