the monoterpenes are best known as components of the ......dr. solomon derese 31 sch 511 the...
TRANSCRIPT
-
Dr. Solomon Derese 31
SCH 511
The monoterpenes are best known ascomponents of the volatile essences offlowers and of the essential oils of herbs andspices, in which they make up as much as 5%of plant dry weight. Monoterpenes areisolated by either distillation or extractionand find considerable industrial use inflavors and perfumes.
Monoterpenes (C10)
-
Dr. Solomon Derese 32
SCH 511Biosynthesis of Monoterpenes (C10)Combination of DMAPP and IPP via the enzymeprenyl transferase yields Geranyl PyroPhosphate(GPP).
OPP
OPPHHR S
OPP
Geranyl Pyrophosphate (GPP)opp
-
Dr. Solomon Derese 33
SCH 511
This produces a monoterpene diphosphate, GeranylPP (GPP), in which the new double bond is E.
Geranyl PP (GPP)
E
-
Dr. Solomon Derese 34
SCH 511
:OPP PPO PPO
:OPP
Z
Linalyl PP (LPP)
-
Dr. Solomon Derese 35
SCH 511
Linalyl PP (LPP) and Neryl PP (NPP) areisomers of geranyl PP, and are formedfrom geranyl PP by ionization to theallylic cation, which can thus allow achange in attachment of thediphosphate group (to the tertiarycarbon in linalyl PP) or a change instereochemistry at the double bond (toZ in neryl PP).
-
Dr. Solomon Derese 36
SCH 511
These three compounds, by relativelymodest changes, can give rise to a rangeof linear monoterpenes found ascomponents of volatile oils used inflavoring and perfumery.
The resulting compounds may behydrocarbons, alcohols, aldehydes, orperhaps esters, especially acetates.
-
Dr. Solomon Derese 37
SCH 511
Acyclic monoterpenesOpen chain monoterpenes are derived from GPP,LPP and NPP by:
Reduction
Oxidation
Dehydration
Using NADPH
Using NADP+
Loss of water
-
Dr. Solomon Derese 38
SCH 511
OPP
GPP
O
Geranial(Lemon oil)
H
O
Citronellal(Citronella oil)
H
OH
(Rose oil)Citronellol
OH
GeraniolGeranium oil
H2O1. H2O
1. H2O
1. H2O
2. NADP+3. NADP+
2.NADPH
2. NADPH
-
Dr. Solomon Derese 39
SCH 511
OPP
GPP
PPO
LPP
-Myrcene (Hops)
HO
Linalool (Coriander oil)
H2O
- HOPP
-
Dr. Solomon Derese 40
SCH 511
OPP
GPP
H2O
O
Neral (Lemon oil)
1. H2O
2. NADP+
-
Dr. Solomon Derese 41
SCH 511
Cyclic monoterpenes
Which of these is ready for cyclization?Cyclization would not be expected to occur with theprecursor GPP, the E stereochemistry of the doublebond being unfavorable for ring formation. NPP or LPP,however, do have favorable stereochemistry, andeither or both of these would act as precursors formonocyclic terpenes.
-
Dr. Solomon Derese 42
SCH 511
LPP
PPO
OPP
NPP
Teritary Carbocation
Menthyl or a-terpinylCarbocation
Menthyl or a-terpinyl Carbocation isthe precursor for many cyclic monoterpenes.
-
Dr. Solomon Derese 43
SCH 511
- H
Limonnene
OH
a-Terpineol
H2O
OHO
Cineole
-
Dr. Solomon Derese 44
SCH 511
HH
H HH
Terpinen-4-yl Cation
Phellandryl cation
Wagner-Meerwein Shift
-
Dr. Solomon Derese 45
SCH 511
Phellandryl cation
a-Phellandrene -Phellandrene
-
Dr. Solomon Derese 46
SCH 511
Terpinen-4-yl Cation- H - H
H2O
a-Terpinene-Terpinene
OH
Terpinen-4-ol
Thujyl cation Sabinene
- H
[O] [H]
Thujone
O
-
Dr. Solomon Derese 47
SCH 511
Pinyl cation
a-Pinene
- H+
- H+
-Pinene
1,2-Alk
yl Shift
Fenchylcation
OH
H2O
FencholO
NADP+
Fenchone
-
Dr. Solomon Derese 48
SCH 511
OH
H2O
Borneol
O NADP+
Camphor
Bornyl Cation
Isocamphyl cation
Camphene
- H+
1,2-Alkyl Shift
-
Dr. Solomon Derese 49
SCH 511
a-terpinyl cation
OPP
GPP
OH
O
OPP
OH
-
Dr. Solomon Derese 50
SCH 511
OPP
OPP
H H
PPOPPO
O OH
Chrysanthemic acid
H2O 2NADP+