... , 5) and pyrimidine - 5 - ketone for BaiSeJing form solid molecular formula for C9H13N5O relative molecular mass 207.2 CA registration number ... h - [1,2,4] triazolo [1, 5 - a] pyrimidin - 5 - one vomit; Nauseant phosphodiesterase IV inhibitor soluble in dimethylformamide, dichloromethane, methanol ... -4H-[1,2,4] triazolo [1,5-a]pyrimidin-5-one vomit; nauseant phosphodiesterase IV inhibitor 27277-00-5