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Terpenes: The Isoprene Rule PowerPoint Presentation
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Terpenes: The Isoprene Rule

Terpenes: The Isoprene Rule

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Terpenes: The Isoprene Rule

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  1. Terpenes: The Isoprene Rule

  2. CH3 H2C CH CH2 C Terpenes • Terpenes are natural products that are structurally related to isoprene. or Isoprene(2-methyl-1,3-butadiene)

  3. CH3 CH2 CH2 CHCH2CH2CCH CH3C Terpenes • Myrcene (isolated from oil of bayberry) is a typical terpene. or

  4. The Isoprene Unit • An isoprene unit is the carbon skeleton of isoprene (ignoring the double bonds) Myrcene contains two isoprene units.

  5. The Isoprene Unit • The isoprene units of myrcene are joined "head-to-tail." head tail tail head

  6. Common Carbon Backbone

  7. Terpenes Classification of Terpenes • Class Number of carbon atoms • Monoterpene 10 • Sesquiterpene 15 • Diterpene 20 • Sesterpene 25 • Triterpene 30 • Tetraterpene 40

  8. OH O H Terpenes Representative Monoterpenes a-Phellandrene(eucalyptus) Menthol(peppermint) Citral(lemon grass)

  9. OH O H Terpenes Representative Monoterpenes a-Phellandrene(eucalyptus) Menthol(peppermint) Citral(lemon grass)

  10. Terpenes Representative Monoterpenes a-Phellandrene(eucalyptus) Menthol(peppermint) Citral(lemon grass)

  11. Terpenes Representative Sesquiterpenes H a-Selinene(celery)

  12. Terpenes Representative Sesquiterpenes H a-Selinene(celery)

  13. Terpenes Representative Sesquiterpenes a-Selinene(celery)

  14. OH Terpenes Representative Diterpenes Vitamin A

  15. OH Terpenes Representative Diterpenes Vitamin A

  16. Terpenes Representative Diterpenes Vitamin A

  17. Common Terpenes

  18. Limonene

  19. Limonene

  20. Rearrangement

  21. Terpenes

  22. Terpenes

  23. Isoprene / Biosynthesis

  24. Terpene Biosynthesis Formation of geranyl pyrophosphate

  25. Farnesyl Pyrophosphate

  26. Formation of Squalene, the Precursor of Cholesterol

  27. Terpenes Representative Triterpene tail-to-tail linkage of isoprene units Squalene(shark liver oil)

  28. Isoprene LinksHeads or Tails?

  29. Squalene, a triterpene, is a precursor of steroids

  30. Steroids • Many hormones are steroids

  31. The B, C, and D rings are trans fused Methyl groups at C-10 and C-13 are called angular methyl groups

  32. The A and B rings are also trans fused in most naturally occurring steroids Substituents on the same side of the steroid ring system as the angular methyl groups are b-substituents Thoseon the opposite side of the plane of the ring system are a-substituents

  33. Biosynthesis of Cholesterol

  34. Synthetic Steroids

  35. TERPENE BIOSYNTHESESin detailIsopentenyl Pyrophosphate:The Biological Isoprene Unit

  36. The Biological Isoprene Unit • The isoprene units in terpenes do not come from isoprene. • They come from isopentenyl pyrophosphate. • Isopentenyl pyrophosphate (5 carbons) comes from acetate (2 carbons) via mevalonate (6 carbons).

  37. O CH3 O CH3COH HOCCH2CCH2CH2OH OH CH3 O O H2C CCH2CH2OPOPOH The Biological Isoprene Unit 3 Mevalonic acid Isopentenyl pyrophosphate

  38. CH3 O O H2C CCH2CH2OPOPOH OPP Isopentenyl Pyrophosphate or Isopentenyl pyrophosphate

  39. OPP OPP Isopentenyl and Dimethylallyl Pyrophosphate Isopentenyl pyrophosphate is interconvertible with2-methylallyl pyrophosphate. • Dimethylallyl pyrophosphate has a leaving group (pyrophosphate) at an allylic carbon; it is reactive toward nucleophilic substitution at this position. Isopentenyl pyrophosphate Dimethylallyl pyrophosphate

  40. Carbon-Carbon Bond Formation in Terpene Biosynthesis