... A facile and convenient synthesis of 9-methyl-3-(1H-tetrazol-5-yl)-4H-pyrido[1,2-a]pyrimidin-4- one potassium more. less. ... Two convenient synthetic methods of anti-allergy agent, 9-methyl-3-(1H-tetrazol-5-yl)-4H-pyrido[1,2-a]pyrimidin-4-one potassium (1a), are described. ...