The biosynthesis of morphine, an alkaloid derived from the opium poppy (Papaver somniferum), is a complex process involving several enzymatic steps. Here is the sequence of key intermediates involved, along with their structures:


1. L-Tyrosine

  • The biosynthesis of morphine begins with the amino acid L-tyrosine.
  • Structure:

2. L-DOPA (L-3,4-dihydroxyphenylalanine)

  • L-tyrosine is hydroxylated to form L-DOPA.
  • Structure:

3. Dopamine

  • L-DOPA undergoes decarboxylation to form dopamine.
  • Structure:

4. (S)-Norcoclaurine

  • Dopamine combines with 4-hydroxyphenylacetaldehyde (formed from L-tyrosine) to produce (S)-Norcoclaurine through a condensation reaction.
  • Structure:

5. (S)-Reticuline

  • (S)-Norcoclaurine is converted to (S)-reticuline through several methylation, hydroxylation, and dehydrogenation steps.
  • Structure:

6. Salutaridine

  • (S)-Reticuline undergoes intramolecular cyclization and enzymatic oxidation to form salutaridine.
  • Structure:

7. Salutaridinol

  • Salutaridine is reduced to salutaridinol via salutaridine reductase.
  • Structure:

8. Thebaine

  • Salutaridinol is acetylated to form thebaine, a precursor of both codeine and morphine.
  • Structure:

9. Codeine

  • Thebaine is methylated to form codeine, an important intermediate in the biosynthesis of morphine.
  • Structure:

10. Morphine

  • Finally, codeine is demethylated to yield morphine, the final alkaloid product.
  • Structure:

These are the main intermediates involved in the biosynthesis of morphine, from L-tyrosine to the final product, morphine.