Diastereoisomers


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Diastereoisomers

 

(also called diastereomers), stereoisomers with several asymmetrical centers in which the configuration of some of the asymmetrical atoms coincides and that of others is opposite. In contrast to optical antipodes, in which the configuration of all asymmetrical centers is opposite and which differ from each other only in the sign of optical rotation (with complete coincidence of all other properties) diastereoisomers differ not only in the extent of optical rotation but also in other physical properties, such as melting point and solubility, in some chemical properties (for example, reaction rates). For example, mesotartaric acid is a disastereoisomer with respect both to (-) -tartaric and (+)-tartaric acid, although the two are optical antipodes. The method of splitting racemic compounds into optically active substances is based on the difference in the physical properties of disastereoisomers. For example, if an optically active base acts on racemic acid, the resultant salts will be disastereoisomers and can be separated by ordinary methods such as crystallization, after which optically active acids are regenerated from the salts. Racemic bases are separated in a similar manner.

References in periodicals archive ?
As a result of the differences in stereochemistry and stability of the formed diastereoisomers, the enantioseparation can occur on achiral stationary phase with different resolutions of product compounds [24, 30].
Construction of calibration curves was done for the diastereoisomers based on the peak areas of the following concentration levels: 1, 5, 10, 20, 40, 60, 80, and 100 [micro]g/L.
We were not able to separate the isomers present in the pheromone volatiles collected from females or synthetic stereoisomers with 2 different chiral columns because the enantiomers of branched aliphatic hydrocarbons do not possess a functional group that permits derivatized into diastereoisomers that could be separated by chromatographic methods or by spectroscopic techniques such as Nuclear Magnetic Resonance (Meierhenrich et al.
The hydroboration of 7a (diastereomeric mixture) resulted in 6- and 7-hydroxy methylacetals 8a and 9a, as a sum of 8 regio- and diastereoisomers (ratio of 8a and 9a was 4 : 1), and also 4% of the corresponding 6(S)-hydroxylactol 10.
However, this enzyme, termed organophosphorus acid anhydrolase (OPAA), hydrolyzes the relatively non-toxic pair of diastereoisomers, C([not equal to])P(+), more rapidly than the toxic pair C([+ or -])P(-) (1).
2a) shows intense reflections at 14.6 [degrees], 17.6 [degrees] 19.8 [degrees], 24.6n of 29 and a series of reflections between 25 and 28 [degrees] of 2 [theta], as typical of a mixture of diastereoisomers A and B (Yao et al.
Dietary intake of hexabromocyclododecane diastereoisomers ([alpha]-, [beta]-, and [gamma]-HBCD) in the Belgian adult population.
catechu; these are diastereoisomers of the 5,7,3',4'-tetrahydroxyflavan-3-ol structure (Figs.
(8) The peaks in the TIC are sometimes split since tetravalent phosphorus atom is asymmetric and if one (or more) carbon atoms are also asymmetric, two (or a power of two) peaks of diastereoisomers with different RI but the same or almost the same mass spectra are observed (soman is a typical example).
Vessman, "Direct separation of captopril diastereoisomers including their rotational isomers by RP-LC using a teicoplanin column," Journal of Pharmaceutical and Biomedical Analysis, vol.