9+9+9Synthesis of N,N '-bis(4-methyloxazol-5-yl)-urea as the key building block of 1,3-bis(4-methyloxazol-5-yl)xanthine towards an improved bronchodilator

4-Methyloxazole-5-carboxylic acid 2 is converted to 4-methyloxazol-5-yl car boxazide 3 in a one-pot reaction with ethyl chloroformate and triethylamine in cold followed by treatment with sodium azide. 3 is transformed to 4-met hyloxazol-5-yl. isocyanate 4 by heating in dry benzene. 4, on reaction with aqueous sodium hydroxide in the presence of benzyltriethylammonium chlorid e and dichloromethane furnish N,N'-bis(4-methyloxazol-5-yl)urea 5, as the k ey building block of the theophylline analogue, 1,3-bis(4-methyloxazol-5-yl )xanthine, a possible improved bronchodiaiator. C-13 NMR spectral intricaci es of the oxazole ring system as an electron withdrawing unit have been dis cussed.