ISSN:
1572-8943
Keywords:
diastereoisomeric salt formation
;
mechanism of optical resolutions
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract The optical resolution of α-phenylethylamine (1) by 2R,3R-tartaric acid (2) was studied in different solvents, the precipitated salts were subjected to thermoanalytical measurements and X-ray powder diffraction. The most efficient resolution can be accomplished by using methanol, the precipitate, an unsolvated salt containing the S-(-)-1⋅2R,3R-(+)-2 salt in abundance, is not a simple mixture of the diastereoisomeric salt pair, but a new modification. In water, ethanol and acetonitrile a reversed, but less effective resolution can be accomplished by precipitation of a hydrate which contains the R-(+)-1 in abundance. The precipitates from water and ethanol also proved to be new modifications. Only the precipitate from acetonitrile is the mixture of the diastereoisomeric salt pair, which can be expected in fractional crystallization of an eutectic forming diastereoisomeric salt pair. The number of different modifications found by changing the solvent in case of this particular salt pair seems surprisingly high, but may occur for other diastereoisomeric salt pairs, too. The existing but not investigated polymorphism can be the explanation for the sometimes very poor reproducibility of the preparative resolutions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1010148221374
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