3- Methyl-4-hydroxyphenylpyruvic acid

Andreana and coworkers have recently used Id in the synthesis of the natural herbicide thaxtomin A [132]. The required dipeptide was obtained under standard Ugi conditions on reaction with 4-nitroindolylacetaldehyde 410, methyl amine 411, 3-hydroxyphenylpyruvic acid 412, and Id. Following the 4CR, the acyclic product was cyclized and epimerized with KOH at 70°C to afford thaxtomin A ( )-syn-413 and its flnh -diastereomer in a 4 1 ratio (Scheme 7.127). The cyclization presumably proceeds through deprotonation of the secondary amide and subsequent intramolecular attack onto the a-ketoamide functionality forming the hydroxy DKP core. 

Vitamin E, as well as vitamin K, plastoquinones and ubiquinones, is formed, in principle, from shikimic acid via 4-hydroxyphenylpyruvic and homogentisic acid. The terpenoid side chain k synthesised from isopentenyl diphosphate, or more precisely from geranylgeranyl diphosphate, which is gradually reduced to phytyl diphosphate. The primary product of biosynthesis is 5-tocopherol other tocopherok are products of its methylation. The biosynthesis of tocotrienok lies in the condensation of homogentisic acid with geranylgeranyl diphosphate. Vitamin E k only synthesised by plants and some cyanobacteria. 

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.)...

Fig. 10.4 Chromatogram of organic acids extracted from the same urine of the patient illustrated in Fig. 10.3, separated as their O-n-butyloxime and trimethylsilyl derivatives under the conditions described in the legend to Fig. 10.2. Peak identifications are 1, lactate 2, glycollate 3, unidentified 4, 2-hydroxy-n-butyrate plus 3-hydroxy-propionate 5, sulphate 6, 3-hydroxybutyrate and 3-hydroxyisobutyrate 7, 2-hydroxyisovalerate 8, 3-hydroxyisovalerate 10, 2-hydroxyisocaproate 11,2-hydroxy-3-methyl-n-valerate 12, phosphate 13,2-oxoisovalerate (peak 1) 14,2-oxoisovalerate (peak 2) 15, 2-oxo-3-methyl-/i-valerate (peak 1) 16, 2-oxo-3-methyl-n-valerate (peak 2) 17, 2-oxoisocaproate 18, citrate 19, 4-hydroxyphenyl-lactate 20, n-tetracosane (standard) 21, n-hexacosane (standard). The separation of O-n-butyloxime-TMS derivatives of the keto acids from the TMS-hydroxy acids and other components is apparent (compare with Fig. 10.3). Note the apparent loss of 4-hydroxyphenylpyruvate. (The horizontal axis represents the time elapsed in minutes from sample injection.)...

Fig. 16.14 Chromatogram of organic acids extracted using solvents from the urine of a patient with hereditary tyrosinaemia and separated as their methoxime and tri-methylsilyl derivatives on 3 per cent OV-17 using temperature programming from 80°C to 260°C at 4°C min Peak identifications are 1, urea plus phosphate 2, succinate 3, 2-methyl-3-hydroxybenzoate (internal standard) 4, 2-oxoglutarate 5, 4,6-dioxo-heptanoate (succinylacetone) 6, 4-hydroxyphenylacetate 7, aconitate 8, citrate 9, isocitrate 10, dihydroxyphenylpropionate 11, 4-hydroxyphenyl-lactate 12, 4-hydroxyphenylpyruvate 13, 3,5-dioxo-octanedioate (succinylacetoacetate). (Redrawn with modifications from Lindblad etal, 1977)...

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