Dihydroxyphenyl pyruvate

The question of when the extra OH groups arc added was also solved by labelling and it was found that dihydroxyphenyl pyruvate was incorporated into both halves but the dihydroxyphenyl-alanine (an important metabolite usually called dopa ) was incorporated only into the isoquinoline half. 

Conversion of p-Hydroxyphenylpyruvic Acid to 2,5-Dihydroxyphenyl-pyruvic and Homogentisic Acids. Function of Ascorbic Acid and of Hematopoietic Factors... 

Knox (483) has purified 100-fold an enzyme converting p-hydroxyphenyl-pyruvate to homogentisate. The system requires either ascorbic acid or dichlorophenolindophenol, and appears to be much more active than systems previously reported. The conversion occurs in one step. Details of the reaction are awaited with interest especially as 2,5-dihydroxyphenyl-pyruvate appears to be neither an intermediate nor an inhibitor (209a). 

Reticuline.—A biosynthetic study of the important benzylisoquinoline reticuline (41), published in preliminary form/ has appeared in full/ Important new information is that 4-hydroxyphenylpyruvic acid (37) and 3,4-dihydroxyphenyl-pyruvic acid (38) are incorporated, like tyrosine, into both C6-C2 units of recticuline (41), in contrast to the transamination product of (38), i.e. dopa (39), which, curiously, is only used for the elaboration of one of these units (ring A and attached ethanamine residue), being incorporated via dopamine (40). Condensation of dopamine with (38) affords (43), which has been shown to be a benzylisoquinoline precursor followed in sequence by (42). The new results confirm these findings by showing that (42) and (43) are reticuline precursors too. 

Working with Litsea glutinosa (Lauraceae), and concentrating on the biosynthesis of reticuline, Bhakuni and co-workers have shown that dopa and dopamine contribute only to the formation of the phenethylamine portion of reticuline. The benzylic portion is biosynthesized from 3,4-dihydroxyphenyl-pyruvic acid not derived from dopa. Tyrosine, 4-hydroxy-, and 3,4-dihydroxy-phenylpyruvic acid all participate in the formation of both halves of the molecule. Norlaudanosoline carboxylic acid, norlaudanosoline, and didehydronor-laudanosoline are intermediates in the biosynthetic sequence 0-methylation precedes W-methylation. ... 

Amino acids can be synthesized via the coupling of Schiff bases with carbanions generated by reduction of benzyl halides [143,144]. Electrolysis of benzyl chloride at mercury in DMF containing TBABr, and in the presence of the Schiff base formed from benzylamine and benzyl pyruvate, affords or-methylphenylalanine in up to 86% yield (after hydrogenolysis over palladium-charcoal). An antihypertensive agent, or-methyl-j6-(3,4-dihydroxyphenyl)alanine, has been prepared by reductive coupling of the aforementioned Schiff base with 3,4-methylenedioxybenzyl chloride. 

Pyruvate inhibits the oxidation of tyrosine and p-hydroxyphenyl-pyruvate, but not of homogentisic acid. This inhibition can be reversed by ascorbic acid or hydroquinone and its site of action, then, appears to be in relation to 2,5-dihydroxyphenyl formation from p-hydroxyphenyl-pyruvate. 

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