Pyrimidine

Pyrimidines include three of the bases in DNA and RNA.
A pyrimidine is an aromatic heterocyclic organic compound, similar to purine. It has nitrogens at positions 1 and 3 in the ring. 
Pyrimidines.
The pyrimidine ring system occurs widely in nature.
It is also found in many synthetic compounds such as barbiturates and the HIV drug, zidovudine. Uric acid is a pyrimidine derivative.