Monoterpenoids

Question 1

What’s the source of most common monoterpenoids?
How are monoterpenoids divided

Answer 1

Source - C10 geranyl GPP –> almost every possible arrangements of 2 isoprene units
Monoterpenoids are divided into: acyclic, monocyclic, bicyclic, iridoids, irregular and mixed.

Question 2

Where can we find monoterpenoids?

Answer 2

They are widely distributed, some in insects and are rare in other organisms.

Major constituents of essential oils (significant in economy- base for flavors, fragrances / perfumes, solvents)

Question 3

List some functions

Answer 3

-ecological function in plants rather than physiological
-herbicides since they help plants to compete among them
-attract or repel insects
-knsect pehromonse

Question 4

What are the main characteristics?

Answer 4

Lipid soluble, colorless, fragrant and volatile, steam distillable, readily separated and analyzed by gas chromatography

Question 5

How are acyclic monoterpenoids formed?

Answer 5

Basically from DMAPP + IPP. Maybe from both GPP into NPP.

Question 6

Citral - applications?

Answer 6

It has a strong lemon smell (bc it an aldehyde) so it’s used on fragrance and cosmetics, food and baking.

Neral is it’s Z isomer.
Citral is a mixture of geranial and neral.

Question 7

Why monoterpenoids have a wide variety, >100 compounds?

Answer 7

Due to the carbocation formation–> delocalization / resonance reaction allows for intramolecular rearrangements.
All subsequent cyclic monoterpenoids originate from it.

Question 8

What bicyclic terpenoids are derived from limonene?
How many classes of bicyclic monoterpenoid

Answer 8

a-pinene and b-pinene.
Camphor, cineole, ascaradiole

7 classes

Question 9

Cyclic monoterpenoids are mainly derived from…?

Answer 9

NPP - neryl diphosphate–> it is folded such that the cyclization is favored, and the final products come from modifications and addition of functional groups.

Question 10

P-menthane skeleton?
What’s pepper mint oil mainly composed of?

Answer 10

P-menthane skeleton is the skeleton for most monocyclic monoterpenoids.

Peppermint oil is made 70% out of menthol (monocyclic monoterpenoid)

Question 11

Monocyclic monoterpenoid examples

Answer 11

Piperitenone, pulegone, menthone, menthol

Same p-menthane skeleton

Question 12

Limonene characteristics

Answer 12

-lemon flavor in lemon tea
-Very important
-rearrangement of double bond compared to NPP
-Found in turpentine, caraway and dill (same compound in multiple instances)
-Often makes racemic mixture
-attracts male boll weevil to cotton

Question 13

Thymol (it’s a phenol) characteristics

Answer 13

-major aromatic monoterpenoid-> gives pungent caustic smell of thyme
- good fungicide
-essential oil from thymus vulgaris

Question 14

Pinene (both are derived from limonene)

Answer 14

• varying: amounts in pine species, from tree to tree, and with age and environmental conditions
  -can be alpha-pinene or beta-pinene
  -alpha is more stable than beta.

Question 15

Camphor (derived from limonene)

Answer 15

-good plasticer, used for explosives, antiseptics, and varnishes.
-from camphor tree(naturally)–> manufacture form pinene (commercially)

Question 16

Cineole (derived from limonene)

Answer 16

-used for respiratory diseases and as antiseptics
-main component of eucalyptus oil
- used in hall’s mentholyptus

Question 17

Ascaridole (derived from limonene)

Answer 17

-from endoperoxidation of limonene
-used as laxative to expel intestinal worms
-insecticide for plant
- in the plant chenopodium

Question 18

A-pinene and b-pinene mechanism

Answer 18

Happens through the carbocation intermediate.
-carbocation –> short lived, stabilized by an enzyme - transition state are not proven. Probb enzyme is in low concentration

Question 19

Iridoids (byciclic)

Answer 19

Ex. Loganin (C11 compound due to Me ester) –> Glucoside
Characterisitcs:
-6 membered lactone ring, connected to a 5 memebered ring.
-Becomes catnip / catmint if Glu, Me and MeOH are gone.
- Water soluble bc of relativeness to glucoside.

-found: in the ants (iridomyrmex) –> iridomyrmecin - derived from NPP (pathway not worked out yet )
in many plants –> not organ specific

uses:
-repellent and irritants - chemical defense for insects –> Natural insecticieds.
-precursor of monoterpenoid alkloids (indoles).

Question 20

Secoiridoid (bicyclic)

Answer 20

ex. Gentiopicroside from oxidation of loganin
No Cyclopentane ( 5 membered ring) rings of iridoids–> cleaved and replaced with extra lactone ring.

Question 21

Mixed and irregular monoterpenoids

Answer 21

-C10 - but are biogenic anomalies of the isoprene rule –> unusual pahtways
-Restricted distribution
-Ex. Camphene and crhysanthemyl

Question 22

Camphene (irregular)

Answer 22

-Looks like bicyclic
-Not made of NPP - rather from Lavandunol which is the fusion between 2 DMAPPs.

Question 23

Pyrethrins - mixed monoterpenoids

Answer 23

From chrysanthemus flower.
-Chrysanthemyl skeleton.
-Insecticide (kills parasites, lice, tick) - environmentally safe unless they go to the sea / river.
-Toxic to fish and insects
-Mammals and plants are okay wiht it.
-Irregular angled ring (strained ring) readily opens.
- Has an R group with polar contituents.

Question 24

Why are mammals and plants immune to some insecticides?

Answer 24

Because the cellular / molecular tagets are different. There are also differences in neurophysiology. This is called selective toxicity.

Question 25

What are the three skeletons of monoterpenoids studied in this class?

Answer 25

p-menthane, lavandul (for camphene-irregular), chrysantemyl (pyretrhin-mixed)