A search for interstellar pyrimidine

We have searched three hot molecular cores for submillimetre emission from the nucleic acid building block pyrimidine. We obtain upper limits to the total pyrimidine (beam-averaged) column densities towards Sgr B2(N), Orion KL and W51 e1/e2 of 1.7 x 10(14), 2.4 x 10(14) and 3.4 x 10(14) cm(-2), respectively. The associated upper limits to the pyrimidine fractional abundances lie in the range (0.3-3) x 10(-10). Implications of this result for interstellar organic chemistry, and for the prospects of detecting nitrogen heterocycles in general, are discussed briefly.