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There are three common naming conventions for specifying one of the two enantiomers (the absolute configuration) of a given chiral molecule: the R/S system is based on the geometry of the molecule; the (+)- and (−)- system (also written using the obsolete equivalents d- and l-) is based on its optical rotation properties; and the D/L system is based on the molecule's relationship to ...
Examples of absolute configuration of some carbohydrates and amino acids according to Fischer projection (D/L system) and Cahn–Ingold–Prelog priority rules (R/S system) The R/S system is an important nomenclature system for denoting enantiomers. This approach labels each chiral center R or S according to a system by which its substituents ...
1-Aminoindane is an aminoindane. [1] It is a racemic mixture of (R)- and (S)-enantiomers. [6] The (R)-enantiomer is -1-aminoindan, which has pharmacological activity and is an active metabolite of the antiparkinsonian agent rasagiline. [2] [4] [5] A number of notable 1-aminoindane derivatives exist. These include the following:
An enantiopure drug is a pharmaceutical that is available in one specific enantiomeric form. Most biological molecules (proteins, sugars, etc.) are present in only one of many chiral forms, so different enantiomers of a chiral drug molecule bind differently (or not at all) to target receptors.
The mixture of enantiomerically pure R and S crystals forms a eutectic mixture. Consequently, the melting point of the conglomerate is always lower than that of the pure enantiomer. Addition of a small amount of one enantiomer to the conglomerate increases the melting point. Roughly 10% of racemic chiral compounds crystallize as conglomerates. [7]
For example, (S-naproxen is an analgesic but the (R-isomer causes renal problems. [31] In such situations where one of the enantiomers of a racemic drug is active and the other partner has undesirable or toxic effect one may switch from racemate to a single enantiomer drug for a better therapeutic value.
An example of a (s) descriptor: (1R,2s,3S)-1,2,3-trichlorocyclopentane. A practical method of determining whether an enantiomer is R or S is by using the right-hand rule: one wraps the molecule with the fingers in the direction 1 → 2 → 3. If the thumb points in the direction of the fourth substituent, the enantiomer is R; otherwise, it is S.
Glyceraldehyde has one chiral center and therefore exists as two different enantiomers with opposite optical rotation: In the D/L nomenclature, either D from Latin Dexter meaning "right", or L from Latin Laevo meaning "left" In the R/S nomenclature, either R from Latin Rectus meaning "right", or S from Latin Sinister meaning "left"