Mandelate purification

The crude product contains varying quantities of sodium carbonate and sodium sulfate, which are difficult to remove. These impurities are insoluble in liquid ammonia consequently the crude compound can be ammonolyzed without further purification. The mandelic acid-acetone condensation product may be purified by recrystallization from absolute alcohol it then melts at 45°. 

S-(0-Methyl)mandelic acid chloride was prepared (14-h reflux in 5 mL of benzene) from the S-(0-methyl)mandelic acid (0.33 g, 2.0 mmol) and oxalyl chloride (0.34 mL, 4.0 mmol). The chloride was added to a solution of 3 (0.56 g, 2.0 mmol) and dry pyridine (0.33 mL, 4.0 mmol) in dry toluene (20 mL) at — 10°C. The mixture was then allowed to attain 0°C. After 14 h, toluene was added, and the mixture was washed with water (20 mL). Toluene solution was dried (MgS04) and concentrated to dryness to yield 4 (0.84, 98%), which was used in the next step without purification. 

Pasteur s original chemical method of resolution, which is still widely used at the present time, involves the formation of diastereoisomeric salts from racemic acids or bases by neutralisation with available optically pure bases or acids respectively. The required optically pure reactants are often available from natural sources and include tartaric, malic and mandelic acids, and alkaloids such as brucine, strychnine, morphine and quinine. Ideally, by appropriate choice of the resolving reagent, the diastereoisomeric salts are crystalline and have solubilities sufficiently different to permit the separation and ready purification of the less soluble salt by fractional crystallisation from a suitable solvent. The regeneration of the optically pure enantiomorph, and incidentally the recovery of the resolving reagent, normally presents no problems. 

The cyanohydrin synthesis of a-hydroxy acids is very often carried out without isolation or purification of the cyanohydrins. The various techniques for the preparation of the cyanohydrins are discussed elsewhere (method 390). Hydrolysis to the a-hydroxy acids is usually effected by heating with concentrated hydrochloric acid. Excellent directions are given for mandelic acid (52% over-all from benzaldehyde), a-methyl-a-hydroxybutyric acid (65% from methyl ethyl ketone), and eighteen dialkyl- and alkylphenyl-glycolic acids (60-80%). Sodium hydroxide solution is used in the preparation of /S-hydroxypropionic acid from the /S-hydroxy nitrile (80%). ... 

H12. Hesketh, J. E., Virmaux, N., and Mandel, P., Purification and characterization of myosin from bovine retina. Biochim. Biophys. Acta 542, 39-46 (1978). 

Helwig, J. J., Farooqui, A. A., Bollack, C., and Mandel, P. Purification and some properties of arylsulfiitases A and B from rabbit kidney cortex. Biochem. J. 165, 127-134 (1977). 

L-form recoveiy from feed in Zone II The conqiosition of L-form in crystals, the crystal yield and the L-form conqxisition of the mother liquor from feed C (L-70%, eutectic conqxisition) are shown in Tsd le I. L-mandelic acid of 79.2% max. purity was obtained, so these crystals can be fed to the separation stqp (Step 2) in Zone I for further purification. The weights of the... 

Okazaki H, Niedergang C, Mandel P (1976) Purification and properties of calf thymus polyadenosine diphosphate ribose polymerase. FEBS Lett 62 255-258... 

Stanier RY, Kunisawa R, Mandel M and Cohen-Bazire G (1971) Purification and properties of unicellular algae (order Chroococcales), Bacteriol. Rev. 35,171-205... 

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