1. Terpenes & Terpenoids 4

2. Terpenes - class of >20,000 compounds containing carbon atoms in multiples of five Terpenoids - oxygen-containing terpenes (alcohols, ketones, aldehydes

3. The name "terpene" is derived from the word "turpentine"
Terpenes and terpenoids are the primary constituents of the essential oils of many types of plants and flowers. 
rose oil
(zencefil)
(kereviz)

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

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

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

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

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

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

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

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

13. Representative SesquiterpenesH
a-Selinene (celery)

14. Representative SesquiterpenesH
a-Selinene (celery)

15. Representative Sesquiterpenes
a-Selinene (celery)

16. Representative DiterpenesOH
Vitamin A

17. Representative DiterpenesOH
Vitamin A

18. Representative Diterpenes
Vitamin A

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

20. Finding the isoprene building block - cyclic compounds
Finding the isoprene building block - sesquiterpenes (C15)

21. Finding the isoprene building block - triterpenes (C30) -
Squalene has a natural and vital part in the synthesis of all plant and animal sterols, including cholesterol, steroid hormones, and vitamin D in the human body

22. Finding the isoprene building block - tetraterpenes (C40) Lycopene is responsible for the red color in tomatoes and watermelon

23.  -carotene is the compound that causes carrots and apricots to be orange

24. ”
C10 terpenoids
The precursor to C10 terpenoids (monoterpenes) is Geranyl pyrophosphate (GPP), also known as geranyl diphosphate (GDP), which consists of two C5 “isoprene units” that are joined “head-to-tail PP
head - tail head - tail

25. Geranyl pyrophosphate

26. C15 sesquiterpenoids
are derived from Farnesyl diphosphate, which consists of three C5 “isoprene units” that are joined “head-to-tail”

28. C20 diterpenoids
are derived from Geranylgeranyl diphosphate, which consists of four C5 “isoprene units” that are joined “head-to-tail”

29. Terpenoid nomenclature
Groups and subgroups
Based on pathways
Classification
IUPAC
CAS
Trivial name(derived from the structural family
Or relate to natural source)

30. Examples of the co-existence of systematics Semi-systemetic and trivial names

31. Menthol – a cyclic terpenoid
This terpene has been
oxidised to a terpenoid

32. Absinthe – a cyclic terpenoid a potent green aniseed-flavoured liqueur, originally made with the shrub wormwood.(the seed of the anise, used in cooking and herbal medicine)
This terpene has been
oxidised to a terpenoid

33. Camphor – a cyclic terpenoid

34. a-Selinene – a cyclic terpene
3 isoprene units
15 carbon atoms

35. β-carotene – a linear terpene
8 isoprene units
40 carbon atoms

36. Which unit makes up every terpene? Isoprene Unit
Questions
Which unit makes up every terpene?
Isoprene Unit
How many carbons are there in an isoprene unit?
Five
What is the systematic name for isoprene?
2-methylbuta-1,3-diene
What is an oxidised terpene known as?
Terpenoid

37. Carvone
Occurs in Enantiomeric forms
Also known as Meridian fennel, Persian carrot
Uses
Carvone –Latin name for Caraway, carum carvi
Basic carbon skeleton
1-isopropyl-4-methylcyclohexane common in nature the genus mentha includes various types of mint

38. saturated ketone of the p- menthane family of monoteroenoids
Greek letters
Use to distinguish between isomeric terpenoids
Depends on
In order in which the isomers were discovered
Their abundance

39. α- Pinene ¾ component of turpentine oil by weight β- Pinene next most significant component

40. Cyclic Terpenoids
α, β, and γ refers to the location of double bond in isomeric olefins
α - endocyclic tri substituted double bond
β- A tetra substituted olefinic bond
γ- exocyclic methylene function
Example E1 reaction

42. α - endocyclic tri substituted double bond
A trisubstituted alkene is an alkene in the molecule of which the doubly bonded carbons are bonded to a total of three carbon atoms excluding each other.

43. A tetrasubstituted alkene is an alkene in the molecule of which the doubly bonded carbons are bonded to a total of four carbon atoms excluding each other.

44. Methylene group γ- exocyclic methylene function

45. THE ROLE OF TERPENOIDS IN NATURE
Terpenoids are produced by a wide variety of plants, animals and micro-organisms.
As for all metabolites, the synthesis of terpenoids places a metabolic load on the organism which produces them and so, almost invariably, there is a role which the material plays and for which it is synthesized.

46. The roles which the terpenoids play in living organisms can be grouped into three classes:
Functional
Defense and (producing resins and gums Acacia gummiferae)
Communication.

47. Examples
Vitamin A, or retinol, is the precursor for the pigment in eyes which detects light and is therefore responsible for the sense of sight.
Vitamin E, or tocopherol, is an important antioxidant which prevents oxidative damage to cells.

48. Vitamin D2, also known as calciferol, regulates calcium metabolism in the body and is therefore vital for the building and maintenance of bone.
Chlorophyll-a is a green pigment found, for example, in plant leaves and is a key factor of photosynthesis through which atmospheric carbon dioxide is converted to glucose.

50. Calciferol

51. Tocopherol

52. Chlorophyll

53. Communication
Terpenoids are also used as chemical messengers.
If the communication is between different parts of the same organism, the messenger is referred to as a hormone.
Giberellic acid is a hormone used by plants to control their rate of growth.
Testosterone and oestrone are mammalian sex hormones. .

56. Oesteron

57. Pheromones
Chemicals that carry signals from one organism to another are known as semiochemicals.
These can be grouped into two main classes.
If the signal is between two members of the same species, the messenger is called a pheromone.
Pheromones carry different types of information.

58. Not all species use pheromones.
In those which do, some may use only one or two pheromones while others, in particular the social insects such as bees, ants and termites, use an array (arrangement)of chemical signals to organise most aspects of their lives.

59. Ants and termites use trail pheromones to mark a path between the nest and a food source.
This explains why ants are often seen walking in single file over long distances.
One such trail pheromone is Neocembrene-A which is produced and used by termites of the Australian species Nasutitermes exitiosus..

60. The social insects also use alarm, aggregation, dispersal and social pheromones to warn of danger and to control group behaviour.

61. Allelochemicals
Chemicals which carry messages between members of different species are known as Allelochemicals. Within this group,
Allomones benefit the sender of the signal,
Kairomones its receiver and with
Synomones both the sender and receiver benefit. Examples are shown in

62. Examples
Camphor and d-limonene are Allomones in that the trees which produce them are protected from insect attack by their presence

63. Similarly, antifeedants could be considered to be allomones since the signal generator, the plant, receives the benefit of not being eaten.
Myrcene is a kairomone, in that it is produced by the ponderosa pine and its presence attracts the females of the bark beetle, Dendroctonous brevicomis.

64. Geraniol is found in the scent of many flowers such as the rose.
Its presence attracts insects to the flower and it can be classified as a Synomones since the attracted insect finds nectar and the plant obtains a pollinator.

65. 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).

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

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

68. Isopentenyl and Dimethylallyl Pyrophosphate
Isopentenyl pyrophosphate is interconvertible with 2-methylallyl pyrophosphate.
OPP
OPP
Isopentenyl pyrophosphate
Dimethylallyl pyrophosphate
Dimethylallyl pyrophosphate has a leaving group (pyrophosphate) at an allylic carbon; it is reactive toward nucleophilic substitution at this position.

69. 26.9 Carbon-Carbon Bond Formation in Terpene Biosynthesis4

70. Carbon-Carbon Bond Formation+
OPP
The key process involves the double bond of isopentenyl pyrophosphate acting as a nucleophile toward the allylic carbon of dimethylallyl pyrophosphate.

71. Carbon-Carbon Bond Formation+
OPP
OPP – +
OPP

72. After C—C Bond Formation...
The carbocation can lose a proton to give a double bond. +
OPP

73. After C—C Bond Formation...
OPP
The carbocation can lose a proton to give a double bond. H – + +
OPP

74. After C—C Bond Formation...
OPP
This compound is called geranyl pyrophosphate. It can undergo hydrolysis of its pyrophosphate to give geraniol (rose oil).

75. After C—C Bond Formation...
OPP
H2O OH
Geraniol

76. From 10 Carbons to 15 +
OPP
Geranyl pyrophosphate +
OPP

77. From 10 Carbons to 15
OPP H – + +
OPP

78. From 10 Carbons to 15
OPP
This compound is called farnesyl pyrophosphate.
Hydrolysis of the pyrophosphate ester gives the alcohol farnesol (Figure 26.6).

79. From 15 Carbons to 20
OPP
OPP
Farnesyl pyrophosphate is extended by another isoprene unit by reaction with isopentenyl pyrophosphate.

80. Rings form by intramolecular carbon-carbon bond formation.
Cyclization
Rings form by intramolecular carbon-carbon bond formation. +
OPP
OPP
E double bond
Z double bond

81. Limonene H – + + OH
H2O
a-Terpineol

82. Bicyclic Terpenes + + + +
a-Pinene
b-Pinene

83. 26.10 The Pathway from Acetate to Isopentenyl Pyrophosphate4

84. Recall
CH3COH O
HOCCH2CCH2CH2OH
CH3 OH O 3
Mevalonic acid
H2C
CCH2CH2OPOPOH
CH3 O
Isopentenyl pyrophosphate

85. Biosynthesis of Mevalonic Acid
In a sequence analogous to the early steps of fatty acid biosynthesis, acetyl coenzyme A is converted to S-acetoacetyl coenzyme A.
CH3CCH2CSCoA O
S-Acetoacetyl coenzyme A

86. Biosynthesis of Mevalonic Acid
CH3CCH2CSCoA O
CH3CSCoA O +
In the next step, S-acetoacetyl coenzyme A reacts with acetyl coenzyme A.
Nucleophilic addition of acetyl coenzyme A (probably via its enol) to the ketone carbonyl of S-acetoacetyl coenzyme A occurs.

87. Biosynthesis of Mevalonic Acid
CH3CCH2CSCoA O
CH3CSCoA O +
CH3CCH2CSCoA
CH2COH HO O

88. Biosynthesis of Mevalonic Acid
Next, the acyl coenzyme A function is reduced.
The product of this reduction is mevalonic acid.
CH3CCH2CSCoA
CH2COH HO O

89. CH3CCH2CH2OH
CH2COH HO O
Mevalonic acid
CH3CCH2CSCoA
CH2COH HO O

90. Conversion of Mevalonic Acid to Isopentenyl Pyrophosphate
CH3CCH2CH2OPP
CH2COH O
OPO3 2–
CH3CCH2CH2OH
CH2COH HO O
The two hydroxyl groups of mevalonic acid undergo phosphorylation.

91. Conversion of Mevalonic Acid to Isopentenyl Pyrophosphate
OPO3 3–
CH3CCH2CH2OPP
CH2 O
OPO3 2– C ••
• • –
CH3CCH2CH2OPP
CH2 O C
Phosphorylation is followed by a novel elimination involving loss of CO2 and PO43–.

92. Conversion of Mevalonic Acid to Isopentenyl Pyrophosphate
CH3CCH2CH2OPP
CH2
The product of this elimination is isopentenyl pyrophosphate.

93. Biosynthetic pathway is based on experiments with 14C-labeled acetate
CH3COH O
HOCCH2CCH2CH2OH
CH3 OH O
Mevalonic acid
H2C
CCH2CH2OPOPOH
CH3 O
Isopentenyl pyrophosphate

94. Biosynthetic pathway is based on experiments with 14C-labeled acetate
Citronellal biosynthesized using 14C-labeled acetate as the carbon source had the labeled carbons in the positions indicated.
CH3COH O
H2C
CCH2CH2OPOPOH
CH3 O O H •