1- ethylamine carboxylic acids resolution

Optica] resolution of these and related carboxylic acids were achieved using salt formation with alkaloids (strychnine, brucine, cinchonidine) 33,39,44 or with optically active amines [1-phenyl- or l-( 3-naphthyl)ethylamine]4o,44). The following rotations [a]D have been reported [8]paracyclophanecarboxylic acid (13) +18° (chloroform)441 [10]homologue (14) +80° (chloroform)39 and +67° (chloroform)40 its methyl-derivative (75) —28° (methanol)44 . Dioxa[10]paracyclophanecarboxylic acid (16) + 104° (ethanol)36 and bromo-dioxa[12]paracyclophanecarboxylic acid (79) —37° (acetone)33). 

Abou-Basha and Aboul-Enein [22] presented an isocratic and simple HPLC method for the direct resolution of the clenbuterol enantiomers. The method involved the use of a urea-type CSP made of hS )-indoline-2-carboxylic acid and (R)-1 -(naphthyl) ethylamine known as the Chirex 3022 column. The separation factor (a) obtained was 1.27 and the resolution factor (Rs) was 4.2 when using a mobile phase composed of hexane-1,2-dichloroethane-ethanol (80 10 10, v/v/v). The (+)-enantiomer eluted first with a capacity factor (k) of 2.67 followed by a (—)-enantiomer with a k of 3.38. Biesel et al. [23] resolved 1-benzylcyclohexane-1,2-diamine hydrochloride on a Chirex D-penicillamine column. Gasparrini et al. [24] synthesized a series of the chiral selectors based on /ra s -1,2 - d i a m i n o eye I o hexane. The developed CSPs were used for the chiral resolution of arylacetic acids, alcohols, sulfoxides, selenoxides, phosphinates, tertiary phosphine oxides, and benzodiazepines. In another study, the same authors [25] described the chiral resolution of /i-aminocstcrs enantiomers on synthetic CSPs based on a re-acidic derivatives of trans- 1,2-diaminocyclohexane... 

Resolution of Carboxylic Acids. The enantiomers of 1-(1-naphthyl)ethylamine are used to resolve racemic carboxylic acids by selective crystallization of diastereomeric salts. For example, crystallization of racemic 3-bromobutyric acid with (R)-(+)-NEA followed by acidification of the diastereomeric salt afforded (S)-(+)-3-bromobutyric acid (eq 1). In the same manner, resolution with (5)-(-)-NEA yielded (R)-(-)-3-bromobutyric acid after liberation of the amine (eq 1). ... 

Chromatographic Resolutions. 1-(1-Naphthyl)ethylamine serves as a chiral derivatization agent useful in preparing diastereomeric amides from racemic acids for chromatographic resolution. For example, various terpenoid acids, after conversion to the diastereomeric amides using (R)-(+)-NEA, were analyzed by HPLC to define the enantiomeric composition (eq 4). Application of the procedure has been used to analyze the enantiomeric purity of several carboxylic acid derivatives. ... 

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