Purine

Purine is a bicyclic heterocyclic compound forming the basis of nucleic acids, coenzymes, and many pharmaceutical agents.

Structure

• A fused bicyclic ring: pyrimidine ring fused with imidazole.
• Molecular formula: C₅H₄N₄
• Found in DNA and RNA (adenine and guanine).
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Synthesis

1. Traube Synthesis

   • Multi-step process starting from 4,5-diaminopyrimidine, formic acid or formamide, then cyclization.
   • Produces purine nucleus.

2. From Hypoxanthine or Xanthine

   • Nitration or alkylation reactions on purine base.
   • Used for making analogs (e.g., allopurinol).

3. Biosynthetic Pathway (Biological Relevance)

   • In vivo, purines are synthesized via IMP (inosine monophosphate).
     • Ribose-5-phosphate → PRPP → IMP → AMP/GMP

Medicinal Uses of Purine and Derivatives

1. Nucleotides: Adenine and guanine are key DNA/RNA components.
2. Anticancer Agents:
   • 6-Mercaptopurine – inhibits DNA synthesis (used in leukemia).
3. Gout Treatment:
   • Allopurinol – xanthine oxidase inhibitor, lowers uric acid.
4. Antivirals:
   • Acyclovir – guanine analog, treats herpes simplex virus.
   • Tenofovir – adenosine analog, used in HIV.

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