Sesquiterpenoids

Question 1

How are sesqt. made?

Answer 1

By the action of prenyl transferase wich catalyzes the condensation reaction of head to tail beween IPP + GPP (DMAPP+IPP) resulting on FPP (farnesyl-PP) wiht three isoprene units.

Question 2

What is the largest and most diverse group of terpenoids?

Answer 2

The sesquit. with +100 basic skeletons, and more than 1000 known compounds derived from FPP.

Question 3

Farnesyl - PP characteristics?

Answer 3

1. Exists in both isomers: cis and trans cofiguration 2-trans, 6-trans and *2-cis, 6-trans *
2. These versatile existance allows it to be an intermediate for plenty of terpenes and terpenoids. like carotenoids, sterols
3. Can become cyclic but needs isomerization first. Cyclization leads to many more basic skeletons.

Question 4

What are the general properties of sesq ?

Answer 4

-Same as monoterpenoids - can be a-, mono-, bi- cyclic, mixed & irregular with many subgroups.

-Hydrophobic generally, not very volatile, most of them are oxygenated.

Question 5

Functions & uses

Answer 5

1. plant and animal hormones
2. phytoalexins –> natural herbicides
3. gungal antibiotics - fungi kiling bacteria
4. Antiumor agent - natural anticancer drug.

Question 6

Acyclic Sesq

Answer 6

Low abundance.
-Most of them come from the alcohol derivative of FPP –> farnesol. Not all - colorless

-used as additive in perfumes
enhances scent, co-solvent because regulates volatility

Doubles to 30C to get squalene –> makes steroids.

Question 7

Cyclic Sesq

Answer 7

-Loss of OPP group triggers cyclization
-Like monoterpenes, carbocation allows a wide range of compounds synthesis + the existance of tans-FPP and cis-FPP.
-Common intermediates can be:
y-bisbolene (not source of ABA), picotaxane (found in plants, can kill cattle), humulene (present in lants - antibacterial).

Question 8

What is the mos studied sesq? Provide characteristics

Answer 8

-Absicic acid - ABA –> monocyclic
It is a plant hormone, associated with senescence- synthesized in the chloroplasts.

Can happen naturally as +, but the - form is also active.
Commercially happens as racemic mixture.

Question 9

How is ABA formed?

Answer 9

Through the formation of an epoxide intermediate of FPP.
Epoxide can be COOH epoxide or the Xanthonin epoxide.

Xanthonin come from the carotenoid Xanthophyll.

ABA has C4 in trans alwas due to steric hindrance, and C2 always cis.

Question 10

Functions of ABA

Answer 10

Potent hormone in plants, leaf abscicion (senescence), inhibits growth (responsible for seed and bud dormancy).
Rehulates stomas by controlling H2O retention in leaves –> avoiding evaporation.
–> ABA conc raises from 10 to 20X under drought conditions.
Up regulation can take just few seconds / minuts - pretty quick.

Question 11

JH - juvabione hormone - how many

Answer 11

At least 3 forms

Question 12

JH formation