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Hypoxanthine is the 6-oxopurine base of inosine.

Inosine is the ribonucleoside of hypoxanthine. Hydrolytic deamination of adenosine replaces its exocyclic amino group with a carbonyl oxygen while retaining its sugar attachment.

Purine is the fused six- and five-membered nitrogen heterocyclic framework underlying adenine and hypoxanthine. Its numbered ring nitrogens distinguish protonation and hydrogen-bonding sites.