Nucleotides: Synthesis and Degradation. Nitrogenous Bases. Planar, aromatic, and heterocyclic Derived from purine or pyrimidine Numbering of bases is “unprimed”. Nucleic Acid Bases. Pyrimidines. Purines. Sugars. Pentoses (5-C sugars) Numbering of sugars is “primed”. Sugars.