Oxalacetic acid ketones

The essential starting material for the total synthesis of ( )-aku-ammigine (21) and (+ )-tetrahydroalstonine (22) was the tetracyclic unsaturated ketone 23 (3). This was prepared by condensation of tryp-tamine hydrochloride with oxalacetic acid monomethyl ester which gave the tetrahydro- 8-carboline 24. 

Reference has already been made to an active form of acetic acid which arises from carbohydrate, fatty acids, ketone bodies, and indirectly also from certain amino acids, and combines with oxalacetate to form citrate. It was at one time suspected that this active acetic acid might be identical with acetyl phosphate ... 

The cycle was originally proposed as a mechanism for the terminal oxidation of carbohydrate. It was always obvious that it must also apply to parts of the protein molecule because several amino acids yield members of the cycle directly—glutamic acid, aspartic acid, and alanine—or indirectly—histidine, proline, arginine, and others. Work carried out during the last decade with the help of specially prepared tissue extracts and of isotopes has produced conclusive evidence in support of the conception that the tricarboxylic acid cycle is also the terminal mechanism of the oxidation of fatty acids and ketone bodies. These substances all form the same derivative of acetic acid—acetyl coenzyme A— which can condense with oxalacetate to form citrate. The pathway leading from various... 

Another point of interest is the relatively high AF value of about —8 Kcal. for the decarboxylation of 3-ketonic acids (oxalacetate, oxalosuc-cinate, acetoacetate). 

In the presence of ammonium chloride, the production of ketone bodies is increased in rat liver homogenates and slices, slices of brain, and possibly in guinea pig kidney cortex. Rat liver slices seem to exhibit this effect only when prepared from well-fed animals. The extra ketosis results from a decrease in oxalacetate brought about by the conversion of a-ketoglutarate to glutamic acid in the presence of the added ammonium ion. ... 

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