Hydroxyisocaproic Hydroxyisovalerate

Fukuda and coworkers have described one of the first applications of the enantioselective hydrolysis of nitriles (Scheme 12.1-6). Using a whole cell biocatalyst optically pure a-hydroxy acids (L-a-hydroxyisovaleric acid and L-a-hydroxyisocaproic acid) have been prepared from the racemates of the corresponding a-hydroxyni-... 

Fig. 3.22. GC separation of keto and hydroxy acids from the urine of a patient with maple syrup urine disease. Top chromatogram, the patient before dietary treatment middle chromatogram, the same patient after two days on a diet bottom chromatogram, a mixture of reference compounds. Peaks 1, lactic acid 2, 2-hydroxyisobutyric acid 3, 2-hydroxybutyric acid 4, pyruvic acid 5, 3-hydroxyisobutyric acid 6, 3-hydroxybutyric acid 7, 2-hydroxyisovaleric acid 8, 2-ketobutyric acid 9, malonic acid (internal standard) 10, 2-methyl-3-hydroxybutyric acid 11, 2-hydroxy-n-valeric acid 12. methylmalonic acid 13, 3-hydroxyisovaleric acid 14a and b, 2-ketoisovaleric acid IS, acetoacetic add 16, 2-hydroxyisocaproic acid 17, 2-hydroxy-3-methylvaleric acid 18a, L-2-keto-3-methylvaleric add 18b, D-2-keto-3-methyl-valeric acid 19, 2-ketoisocaproic acid. Reproduced from [386],...

Fig. 10.1 Metabolites in the urine of an untreated patient with branched-chain keto aciduria (maple syrup urine disease). Extracted using ethyl acetate and separated as their trimethylsilyl-oxime derivatives on a 25 m SE-30 capillary column, using temperature programming from 80°C to 110°C at 0.5°C min and an injection split ratio 1 12 at a temperature of 250°C. The peaks marked R are due to solvent and reagents. Peak identifications are 1, lactic 2, 2-hydroxyisobutyric 3, 2-hydroxybutyric 4, pyruvic 5, 3-hydroxybutyric 6, 2-hydroxyisovaleric 7, 2-oxobutyric 8, 2-methyl-3-hydroxy-isovaleric 10, a and b, 2-oxoisovaleric 11, acetoacetic 12, 2-hydroxyisocaproic 13, 2-hydroxy-3-methyl- -valeric 14, 2-oxo-3-methyl-/i-valeric (14a L- 14b D-) 15, 2-oxoisocaproic acids. The internal standard was malonic acid. (Redrawn with modifications from Jellum etal., 1976)...

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. 10.5 Mass spectra of the ethoxime-trimethylsilyl derivatives of (a) 2-oxoisovaleric, (b) 2-oxo-3-methyl-n-valeric (peak 1), (c) 2-oxo-3-methyl-/i-valeric (peak 2) and (d) 2-oxoisocaproic acids and the trimethylsilyl derivatives of (e) 2-hydroxyisovaleric, (f) 2-hydroxy-3-methyl-rt-valeric and (g) 2-hydroxyisocaproic acids.

---