Enantiomers, specificity, range values

If the enantiomer specificity is expressed by the separation factor a, [the ratio of the distribution coefficients between solution and polymer of L- andD-form] values of cx in this and similar cases range from 1.20 to 3.66 depending upon the equilibration conditions and polymer structure. The highest a-value obtained to date was 3.66. In this case, the simple batch procedure gives an enrichment of 13% of the L-form in the filtrate and 40% of the D-form on the polymer (23). 

Values for the enantiomer ratio found in natural products can range from 0% to 100%. If the enantiomeric purity is 100%, care must be taken to determine which isomer is present by comparison of retention times with a known standard. Samples from different geographic or growing regions may show some variation in the ratio of a specific compound, while others will not deviate from a known value. 

Die specificity of the dopamine receptor was further studied with a series of dopaminergic antagonists of well known pharmacological activity. The 30-40% inhibitory effect of 10 nM dopamine was completely reversed by the addition of increasing concentrations of the potent neuroleptics (+)butaclamol (Kp = 1.5 nM) and (-)sulpiride (Kp = 0.5 nM) while their pharmacologically weak enantiomers (-)butaclamol and (+)sulpiride were 86 and 167 times less potent, respectively. The neuroleptics spiroperidol, thioproperazine, domperidone, haloperidol, fluphenazine and pimozide completely reversed the inhibitory effect of dopamine at low Kp values ranging from 0.02 to 0.8 nM (41). 

When the above equations are satisfied, then t = tr for each respective solute. It is seen with the aid of a computer the value of (t) that satisfies equations (17) and (18) can be identified for a specific program rate, the retention time (h) can be calculated. In addition, if the program is run for the second enantiomer, then the ratio of the retention times of the two isomers can be calculated (the separation ratio) for a range of different solvent program rates. 

EH-catalyzed hydrolysis of a racemic epoxide, resulting in the formation of a vicinal diol with an enantiomeric excess of 100%>eep>0% at complete conversion (c=100%) of the substrate. Depending on the EH-substrate interactions and consequently its substrate-related enantiomeric ratio or f-value (which characterizes the ability of the enzyme to discriminate between the two competing substrate enantiomers [1]), enantiopure epoxide are obtained at a specific degree of conversion within the range of 50%rapid hydrolysis of the preferred epoxide enantiomer, followed by a much slower hydrolysis of the remaining epoxide. 

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