4- Hydroxy-2-oxoglutarate

Scheme 4. Directed syntheses of both enantiomers of 4-hydroxy-2-oxoglutarate...

Hydroxy-2-oxoglutarate aldolase Origin E.coli Fluka... 

Metabolism of L-A-hydroxyproUne. EC 1.5.1.12,1-pyrroline-5-carboxylate dehydrogenase. EC 1.5.99.7, 4-hydroxyproline dehydrogenase. EC 2.6.1.23, 4-hydroxyglutamate aminotransferase. EC 4.1.3.16, 4-hydroxy-2-oxoglutarate aldolase. 

N-Alkylated 2-oxoglutaric acid derivatives cyclize at neutral pH values to two epimeric 5-carboxy-5-hydroxy-2-oxopyrolidine structures (Chart 4). In this way, ot-hydroxycarboxylic acid groupings are formed that can act as ligand sites for Fe ". ... 

This enzyme [EC 1.14.11.1], also known as y-butyrobe-taine, 2-ketoglutarate dioxygenase, catalyzes the reaction of 4-trimethylammoniobutanoate with S-keto-glutarate (or, 2-oxoglutarate) and dioxygen to yield 3-hydroxy-4-trimethylammoniobutanoate, succinate, and carbon dioxide. Both iron ions and ascorbate are needed as cofactors. 

This enzyme [EC 4.1.3.17], also known as 4-hydroxy-4-methyl-2-oxoglutarate aldolase and 4-hydroxy-4-methyl-2-oxoglutarate pyruvate-lyase, catalyzes the reversible conversion of 4-hydroxy-4-methyl-2-oxoglutarate to pro-... 

In plants accumulating anthocyanins, flavonols, and proanthocyanidins, naringenin is stereospecifically hydroxylated at position 3 of the C-ring (C3) by the 2-oxoglutarate-dependent dioxygenase flavanone 3-hydroxylase (F3H, EC 1.14.11.9) to yield the 3-hydroxy-trans-flavanone (syn. dihydroflavonol) dihy-drokaempferol [Springob et al., 2003] (Fig.21 2). Dihydroquercetin (3, 4, 5,5, 7-... 

Hydroxy-4-oxoglutaral- dehyde 0.07 Absent Absent 0.07 Absent... 

X-Ray data on vincamine 2-oxoglutarate have been reported980 and the structure of 10,12-dichloro-2,l6-dihydro- 16-hydroxy-2-methoxytabersonine (187) has been confirmed,986 also by the X-ray method. 

While in the presence of 2-oxoglutaric acid neither decarboxylation nor acyloin condensation had been observed, as expected from previously published results (75), we succeeded in the enzymatic conversion of the mono ethyl ester 3 to ethyl 4-oxobutanoate 4, using both whole yeast cells (Saccharomyces cerevisiae) and purified PDC. The oxo ester 4 served as substrate for a second reaction catalyzed by PDC. Formation of a new carbon-carbon bond was accomplished in the presence of pyruvic acid which acted as donor of a C2-unit. Thus, ethyl 4-hydroxy-5-oxohexanoate 5 was obtained for the first time as the result of an enzymatic acyloin condensation. Finally, traces of acid induced the lactonization of hydroxyester 5, indicating it as direct precursor of solerone 1 (Figure 1). 

The biogenesis of solerone 1 and related compounds was successfully rationalized by biomimetic model reactions. As key step we established the pyruvate decarboxylase catalyzed acyloin condensation of pyruvic acid with ethyl 4-oxobutanoate 4 or ethyl 2-oxoglutarate 3 with acetaldehyde. The importance of the ethyl ester function in 3 and 4 serving as substrates for the enzymatic formation of a-hydroxy ketones 5 and 6 was demonstrated. The identification of six yet unknown sherry compounds including acyloins 5 and 6, which have been synthesized for the first time, confirmed the relevance of the biosynthetic pathway. Application of MDGC-MS allowed the enantiodifferentiation of a-ketols and related lactones in complex sherry samples and disclosed details of their biogenetic relationship. 

A mixture of dimethyl 3-oxoglutarate and 5-dimethylamino-1-phenyl-1,4-pentadiene-3-one in dioxan containing acetic acid and potassium fluoride upon refluxing overnight underwent Michael addition and afforded dimethyl 2-hydroxy-4-(2-phenylethenyl)-1,3-benzenedicarboxylate in 63% yield (ref.51). 

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