A heterocyclic organic compound (1) containing nitrogen atoms at positions 1 and 3. Naturally occurring derivatives of the parent compound are of considerable biological importance as components of nucleic acids and coenzymes and, in addition, synthetic members of this group have found use as pharmaceuticals. 1
See also Coenzyme;
Nucleic acid.
Pyrimidine compounds which are found universally in living organisms include uracil (2), cytosine (3), and thymine (4). 2

3

4

Together with purines these substances make up the “bases” of nucleic acids, uracil and cytosine being found characteristically in ribonucleic acids, with thymine replacing uracil in deoxyribonucleic acids. A number of related pyrimidines also occur in lesser amounts in certain nucleic acids. Other pyrimidines of general natural occurrence are
orotic acid and
thiamine (vitamin B
1).
See also Deoxyribonucleic acid (DNA);
Purine.
Among the sulfa drugs, the pyrimidine derivatives, sulfadiazine, sulfamerazine, and sulfamethazine, have general formula (5). 5

These agents are inhibitors of
folic acid biosynthesis in
microorganisms. The
barbiturates are pyrimidine derivatives which possess
potent depressant action on the central nervous system.
See also Sulfonamide.