Of a-hydroxy carboxylic acids

Nitrile groups m cyanohydrins are hydrolyzed under conditions similar to those of alkyl cyanides Cyanohydrin formation followed by hydrolysis provides a route to the preparation of a hydroxy carboxylic acids... 

The carbocations generated by non-Kolbe electrolysis can rearrange by alkyl, phenyl or oxygen migration. The migratory aptitudes of different alkyl groups have been studied in the rearrangement of a-hydroxy carboxylic acids (Eq. 34) [323]. 

Making use of the same reaction principle, disubstituted ketenes 66 have been reacted with aldehydes 80 to form p-lactones 81 [100], with diazo-compounds 82 to form 1,2-diazetidin-3-ones 83 [101] and with nitroso-compounds 84 to form 1,2-oxazetidin-3-ones 85 as precursors of a-hydroxy carboxylic acids (Fig. 42) [102],... 

Periodate oxidative cleavage of a-hydroxy carboxylic acids, RCHOHC02H... 

Various combinations of reactant(s) and process conditions are potentially available to synthesize polyesters [Fakirov, 2002 Goodman, 1988], Polyesters can be produced by direct esterification of a diacid with a diol (Eq. 2-120) or self-condensation of a hydroxy carboxylic acid (Eq. 2-119). Since polyesterification, like many step polymerizations, is an equilibrium reaction, water must be continuously removed to achieve high conversions and high molecular weights. Control of the reaction temperature is important to minimize side reactions such as dehydration of the diol to form diethylene glycol... 

Oxidations. This reagent oxidizes sulfides to sulfoxides in refluxing chloroform in 70 90% yield. It effects oxidative decarboxylation of a-hydroxy carboxylic acids to the noraldchydc in 85 90% yield (equation I). It also oxidatively cleaves aromatic compounds of the type ArCOCHjBr to ArCOOH in about 75% yield.1... 

Oxidative decarboxylation.1 Sodium hypochlorite is known to effect oxidative decarboxylation of a-hydroxy carboxylic acids to form ketones and C02, but a hydroxyl group is not essential since trisubstituted acetic acids are also subject to this oxidation. Thus triphenylacetic acid is oxidized by NaOCl to triphenylmethanol and benzophenone. In the presence of a phase-transfer catalyst, the rate is enhanced... 

The enantioselective iodolactonization of a-hydroxy carboxylic acid derivatives is achieved by using a stoichiometric amount of the chiral titanium reagent (8) (eq 18). ... 

Optically active cyanohydrins are synthetic precursors of a-hydroxy carboxylic acids, a-amino carboxylic acids, /1-hydroxy amines, and several other classes of organic compound of biological importance [146]. Several efficient catalysts have been developed by using titanium as the central metal. 

Degradative oxidation of a-hydroxy carboxylic acids furnishes aldehydes or ketones. Glycolic acid, lactic acid, and mandelic acid are converted into formaldehyde, acetaldehyde, and benzaldehyde, respectively, in 50% yields on refluxing with A -bromosuccinimide in water [745]. Periodates, with phase-transfer reagents, convert a-hydroxyhexanoic acid and mandelic acid into valeraldehyde and benzaldehyde in respective yields of 90 and 88% (equation 478) [776, 778]. 

Weerman degradation. Formation of an aldose with one less carbon atom from an aldonic acid by a Hoffmann-type rearrangement of the corresponding amide. This is a general reaction of a-hydroxy carboxylic acids. 

Derivatives of a-hydroxy carboxylic acids are currentiy used in some cosmetic preparations. 

Hydrolysis of at-halo carbonyl compounds must be effected very cautiously since the resulting -hydroxy carbonyl compounds are sensitive to alkali. An aqueous suspension of barium carbonate has been used for preparation of 2-hydroxy-3-phenylpropionaldehyde.521 The preparation of a-hydroxy carboxylic acids is important Witzemann522 has given details for preparation of glycolic acid, and Bischoff and Walden523 recorded that of 2-hydroxybutyric acid ... 

Ross-Petersen, K.J., and H. Hjeds Syntheses of Some Derivatives of a-Hydroxy-carboxylic Acids. Dansk. Tidsskr. Farm. 43, 188 (1969). 

An example of an exo-trig process would be lactonization of a -hydroxy carboxylic acid ... 

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