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Guanine
Purinones
Year introduced: 1968
Purines
A series of heterocyclic compounds that are variously substituted in nature and are known also as purine bases. They include ADENINE and GUANINE, constituents of nucleic acids, as well as many alkaloids such as CAFFEINE and THEOPHYLLINE. Uric acid is the metabolic end product of purine metabolism.
Hypoxanthines
Purine bases related to hypoxanthine, an intermediate product of uric acid synthesis and a breakdown product of adenine catabolism.
Year introduced: 1966(1964)
Heterocyclic Compounds, 2-Ring
A class of heterocyclic compounds that include a two-ring fused structure. Both aromatic and non-aromatic ring structures are included in this category.
Year introduced: 1998
Heterocyclic Compounds
Cyclic compounds that include atoms other than carbon in their ring structure.
Heterocyclic Compounds, Fused-Ring
Multiple ring heterocyclic compounds containing two or more rings that share two atoms and one bond in common.
Year introduced: 2017