Acetyl mandelic acid

By this method, for example, the absolute configurations of the following compounds were established (-)-2-phenylbutyric acid,[48] (-)-hydratropic acid,[48] (+)-0-acetyl-mandelic acid,t48] (-)-2-(7/-carbazolyl)propionic acid,t48] (+)-1 -phenylethanol,[48] (-)-menthol,t48] (+)-1 -phenylethylamine,[48] and 1-alanine ethylester.[48] The determination of the absolute configuration of bacteriochlorophylles c, d and e was made possible by the esterification of the phaeophorbides by CDI to imidazolides.[49]... 

In a 500-cc. Claisen distilling flask with a low side-tube connected to a condenser, are placed 105 g. of mandelic acid (m.p. xi8°) and 151 g. of acetyl chloride. A reaction sets in without the application of heat (Note 1). As soon as a clear solution results, the flask is warmed on a water bath and the excess acetyl chloride is distilled. The last trace of acetyl chloride may be removed by prolonged drying in a vacuum. The acetyl mandelic acid then crystallizes in large, round, white clusters after one or two days standing. The yield is I3° I33 g- (97 99 Per cent the theoretical amount) (Note 2). 

To the crude acetyl mandelic acid still containing some acetyl chloride obtained as described above, is added 250 g. of thionyl chloride. The reaction starts at once without warming but it is necessary to reflux for four hours to complete the reaction (Note 3). The excess thionyl chloride is then distilled... 

The melting points given in the literature range from 39 to 8o°. The acetyl mandelic acid is difficult to crystallize but may be purified from benzene or chloroform, preferably the former. The product thus obtained melts at about 79-80°. 

Prolonged refluxing of the acetylated mandelic acid with the thionyl chloride tends to lower the yield. 

Acetyl mandelic acid was described by Naquet and Lougui-nine,1 but their product has been shown to be contaminated with the ethyl ester of acetyl mandelic acid. Dupont2 obtained the compound by the oxidation of diacetyl 1, 4-diphenylbutine-2-diol-i, 4. Anschutz and Bocker3 prepared acetyl mandelic acid, and from it the acid chloride, by the use of phosphorus pentachloride, but with poor yields. Von Braun and Muller 4 state that acetyl mandelyl chloride can be made from acetylated mandelic acid and thionyl chloride, the resulting product being a viscous yellow oil. 

Compound ( )-223 was O-deacetylated and again protected with MOM groups to give ( )-224 (94%) (Scheme 29).103 O-Deisopropylidenation of ( )-224 with aqueous acetic acid, followed by esterification with ( S )-(9-acetyl mandelic acid gave a mixture of the (S)-O-acetylmandelates, which were separable by column chromatography to give the enantiomers d-225 (48%) and l-226 (49%), and these were depro-tected to give quantitatively the respective amino alcohols d-50 and l-51. 

A separation of the racemic mixture of chiral zirconocene compounds into the optically active pure enantiomers is performed using 0-acetyl-(/ )-mandelic acid as chiral auxiliary (Structure 28). Using this enantiomerically pure metallocene in oligomerization experiments confirms the mechanistic hypothesis of stereospecificity predicting the topicity of insertion [69]. 

Biphenyl-bridged bis-Cp titanocene dichloride and dimethyl complexes have been synthesized, and the kinetic resolution of the racemic final mixture of the products has been carried out. A mixture of diastereomers is obtained by treatment of the dimethyl compound with O-acetyl-mandelic acid, while enantiomerically pure products result in the reaction of the dichloro derivative with (i )-binaphthol and 1 equiv. of LiBun (Scheme 661).1050... 

Parker, D. Taylor, R. J. Direct NMR Assay of the Enantiomeric Composition of Amines and jS-Amino Alcohols Using O-Acetyl Mandelic Acid as a Chiral Solvating Agent. Tetrahedron 1987, 43 (22), 5451. 

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