4- Hydroxyphenyl-lactic acid

On standing in alkali in the laboratory, prephenic acid rearranges to 4-hydroxyphenyl-lactic acid with specific incorporation of deuterium label as shown. Suggest a mechanism, being careful to draw realistic conformations. 

Aeruginosins, a main class of cyanobacteria peptides characterized by a derivative of hydroxyphenyl lactic acid (Hpla) at the N-terminus, 2-carboxy-6-hydroxyoctahydroindole (Choi) and the arginine derivative agmatine at the C-terminus. The aeruginosins 98-A and B from the blue-green alga Microcystis aeru -nosa act as trypsin inhibitors [M. Murakami et al.. Tetrahedron Lett. 1995, 36, 2785]. 

Gjessing, L. R., Studies of functional neural tumors V, urinary excretion of 3-methoxy-4-hydroxyphenyl lactic acid, Scand. J. Clin. Lab. Invest. 15 (6), 649 (1963). 

Prephenic acid (86) is readily transformed with acid to give phenyl pyruvic acid (89) but is somewhat more stable towards alkali. However, on heating or prolonged standing in dilute alkaline solution it is converted to p-hydroxyphenyl lactic acid (87). Several proposals have been put forward to account for the formation of this product under these conditions and one of these is shown in Figure 2.13. 

A significant increase in the measured COj concentration was observed after the addition of 10 mmol/1 of a-keto-isovaleric acid (148% increase from baseline), a-keto-isocaproic acid (120%), phenylacetic acid (100%), DL-a-keto-P-methyl-A-valeric acid (100%), homogentisinic acid (50%), P-phenylpyruvic acid (45%), hydroxyphenyl acetic acid (32%), propionic acid (25%), ace-toacetic acid (25%), hydroxyphenyl pyruvate acid (23%), and 20 mmol/1 of hydroxyphenyl lactid acid (65%) or salicylic acid (76%). A significant decrease was observed after the addition of 20 mmol/1 of ascorbic acid (33%), DL- -hydroxybutyric acid (25%) or imidazole lactic acid (25%). No effect after the addition of 10 mmol/1 of imidazole-4-acetic acid, methylmalonic acid, 5-hy-droxyindole acetic acid or 20 mmol/1 arginosuccinic acid, Z.-(+)-hydroxybu-tyric acid (E525). 

The presence of another contaminant peak in L-tryptophan implicated in EMS was detected upon HPLC with both UV and FL analyses by Toyo oka et al.9 and was characterized as PAA by Goda et al.7 Adachi et al.15 studied the metabolism of PAA in rats and described four metabolites of PAA in the urine (N-(hydroxyphenyl)glycine, N-phenylglycine, 3-(phenylamino)lactic acid, and 3-(hydroxy-phenylamino)-lactic acid). The results suggested that the degradation pathway of PAA was similar to that of phenylalanine. Other studies with PAA are described in Section 11.10. 

Tyrosyluria 4-Hydroxyphenylpyruvic, 4-hydroxyphenyl-lactic and 4-hydroxyphenylacetic acids Tyrosine Delayed maturation of 4-hydroxy-phenylpyruvic acid oxidase (EC 1.13.11.27) 16.5.2... 

Fig. 10.3 Chromatogram of organic acids extracted from the urine of an untreated patient with branched-chain keto aciduria (maple syrup urine disease), extracted and separated as described in the legend to Fig. 10.2. The chromatogram illustrates the overlapping peaks in the regions occupied by 3-hydroxybutyric, 2-hydroxyisovaleric and 2-oxoisovaleric acids (peak 1) and 2-oxo-3-methyl-valeric, 2-hydroxyisocaprioic and 2-oxoisocaproic acids (peak 2) and phosphate (peak 3). Other peaks of interest are (4) citric, (5) 4-hydroxyphenyl-lactic, (6) 4-hydroxyphenylpyruvic, (7) n-tetracosane (standard) and (8) -hexacosane (standard). (Compare with Fig. 10.4.)...

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