Download - Aromatenbiogenese Für die Diskussion der Aromatenbiogenese werden Kenntnisse der Claisen-Kondensation, der Aldolreaktion, der C-H-Acidität und einiger

Aromatenbiogenese

Für die Diskussion der Aromatenbiogenesewerden Kenntnisse der Claisen-Kondensation, der Aldolreaktion, der C-H-Acidität und einiger sigmatroper Umlagerungen benötigtund im folgenden parallel besprochen.

Modul A: Bioorganische Chemie und Naturstoffchemie, SS 2005, H.D.Martin, Kapitel 01_Aromaten

Malonyl-CoA entsteht aus Acetyl-CoA durchCarboxylierung (Carboxy-Biotinyl-Enzym)


Die Carbonsäure wird zu einem Thioester (ein Coenzym-A) aktiviert:

Cysteamin, ß-Alanin, Pantoinsäure, PP, Adenosin


Eine neue C-C-Bindung wird geknüpft, durch eine Claisen-ähnliche Kondensation:

In der Polyketid-Biosynthese werden C-C-Bindungen durch eine Decarboxylative-Kondensation geknüpft, die irreversibel abläuft und einen Malonsäure-Thioester benötigt. Dabei entsteht im Produkt ein -Keto-Thioester.


Claisen-Kondensation mitMalonyl-CoA zumPolyketid (nicht gezeichnet),Enolisierung zum Triphenol,Cyclisierung zum Flavanon


FLAVONOIDSFLAVONOIDS

Plant Pigments


PLANT PIGMENTSPLANT PIGMENTSFlavonoids and anthocyanins are conspicuous plant pigments in nature thatare responsible for the beauty and splendor of flowers, fruits, fruit tree blossoms and of the autumn leaves.

Flavones are responsible for the yellow and orange colors; and the anthocyaninsare the source of red, violet and blue colors. These compounds occur mainly inhigher plants and are less common in the lower orders. You don’t find them inalgae, fungi or bacteria.

The flavonoids play a major role in attracting insects to feed and pollinate theseplants. Some of them also have a bitter taste and repel harmful insects like caterpillars.

Flavonoids are thought to be antioxidants, and play a major role in our diet, preventing the ravages of aging caused by free-radicals.

These compound have their biosynthetic origin in both the skimic acid pathwayand the acetogenin pathway - they are of hybrid origin.


NARINGENINNARINGENIN

O

CoAS

OH

malonyl-CoA3x

OH

SCoA

OO

O

O

OH

OH O

OH

O

:

OH

OH O

OH

O

H

naringenin

A FLAVONE

internal Claisenand enolizations

A different starterthan acetyl-CoA.

acetogeninpathway

shikimic acidpathway

MIXED-ORIGINCOMPOUND

found in many fruits

Michaeladdition

flavones are yellowor orange pigments


AnthocyaninFlower Pigments


Anthocyanin Leaf PigmentsAutumn Leaves

In Spring and Summerchlorophyll (green) masksthe anthocyanin colorsandin mountain birch (Betula pubescens)early autumn colour change (i.e. highdegree of autumn colouration in Sep-tember) was negatively correlated with insect damage the following season


OH

OH O

OH

O

R

naringenin (R=H)

OH

OH O

OH

O

OH

R

OH

OH O

OH

OH

OH

R

NADPH

[O]

OH

OH O

OH

OH

OH

R

OH

OH

OH O

OH

OH

R

+

- 2 H2O

O2

pelargonidin (R=H)cyanidin (R=OH)

ANTHOCYANIDINS AND ANTHOCYANINSANTHOCYANIDINS AND ANTHOCYANINS

plant flower andleaf pigments

ANTHOCYANIDINScyanidin is bluepelargonidin is pink

Anthocyanins arered, violet or bluepigments.


Aldol-Addition und Kondensation: basisch und sauer (Gleichgewichte !)


glycolysis

PEP

GLUCOSE

Acetyl-CoA

pentose phosphatepathway

Erythrose-4-phosphate

Phosphoenol pyruvate

Shikimic Acid

ORIGINS OF THEORIGINS OF THESHIKIMIC ACIDSHIKIMIC ACIDPATHWAYPATHWAY

The pentose phosphatepathway is one that converts glucose intosugars of different sizes(different numbers of C)by acyl interchanges.Erythrose is a 4-carbonsugar.


OH P

O

O

O C

CH2

COOH

O

OH HCH2

OH

H

H

PO

H+

H

OH

erythrose-4-phosphate

phosphoenol pyruvate

O C

CH2

COOH

OH

OH H

OHH

H

CH2OP

O

O

OH

O C

CH2

COOH

OH

OH H

CH2H

OH

H+

O

OH

OH

H

OHCOOH

O

OH

OH

COOH

OH

OH

OH

COOH

shikimic acid

NADPH

H+

FORMATION OF SHIKIMIC ACIDFORMATION OF SHIKIMIC ACID

B:


FORMATION OF CHORISMIC ACIDFORMATION OF CHORISMIC ACID

OH

OH

OH

COOH

shikimic acid

ATP

O

OH

OH

COOH

P

C O

CH3

COOHpyruvic acid

H+

hydrolysisof PEP

O

OH

O

COOH

P C

CH3

COOH

OHO

OH

O

COOH

P C

CH2

COOH

H

OH

O

COOH

C

CH2

COOH

chorismic acid

:B- H2O

nucleophilicaddition to C=O

- H3PO4


PREPHENIC ACIDPREPHENIC ACID

O CCH2

COOH

C

O

OHH

OH

chorismic acid

Claisen TypeRearrangement

OH

H

CH2

CO

HOOC

C

O

O H

prephenic acid

H OH

CH2HOOC C

O

COOH

phenypyruvic acid

p-hydroxy-phenylpyruvicacid

NADP+NADPH

- CO2-H+ -H-

Prephenic acid can be converted to phenylpyruvic acidor to 4-hydroxyphenylpyruvic acid:

tyrosine phenylalanine

- CO2-H+ -OH

pseudoaxial conformation


CLAISEN REARRANGEMENTCLAISEN REARRANGEMENT

O

CHR

an allyl ether

heat O

CHRH

OH

CHR

an allyl phenol

enolization

H+

A THERMAL REARRANGEMENT


PREPHENIC ACID TO PHENYLALANINEPREPHENIC ACID TO PHENYLALANINE

OH

H

CH2

CO

HOOC

C

O

O H

prephenic acid

:B-Enz

H+

CH2 C

O

COOH

transamination

phenylpyruvic acid

CH2 CH COOH

NH2

phenylalanine

- CO2

- H2O


Download - Aromatenbiogenese Für die Diskussion der Aromatenbiogenese werden Kenntnisse der Claisen-Kondensation, der Aldolreaktion, der C-H-Acidität und einiger

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