JMDMT #486 Microfossils of Cyanobacteria in Carbonaceous Meteorites

The James M. DuPont Meteorite Collection -in the presence of calcium oxide.- Synthesis of Purines and Purine Intermediates The formation of purines on the primitive Earth or in cosmic bodies pose a priori a difficult conceptual problem because it requires the formation of two fused heterocyclic structures, an imidazole and a pyrimidine. In principle, there are, however, two relatively simple mechanisms or path- ways which can be visualized for the formation of the purine ring. One involves condensation of a 3-carbon compound with a 1-carbon reactant to form a 4,5- disubstituted imidazole and the other involves condensation of a C3 compound with a Ci reactant to form a 4,5-disubstituted pyrimidine. The reaction terminates by cyclization of either the disubstituted imidazole or the disubsti- tuted pyrimidine with another mole of the Ci