Chiral index

Epimers Ratio Index. Chiral centers occur in the materia prima in one definite configuration. The degree of epimerization of these centers in the materia actuale have been interpreted as a measure of the degree of maturation of the sediments. 

The Wiener index for isopentane is 18. The Wiener index is used as a mathematical descriptor used in structure - property relationships. There are many other related descriptors for molecular graphs, including shape index, chirality index, Szeged index [12]. A comparison of the boiling points of alkanes against the different indices has been shown in the literature [13]. 

Antineoplastic Drugs. Cyclophosphamide (193) produces antineoplastic effects (see Chemotherapeutics, anticancer) via biochemical conversion to a highly reactive phosphoramide mustard (194) it is chiral owing to the tetrahedral phosphoms atom. The therapeutic index of the (3)-(-)-cyclophosphamide [50-18-0] (193) is twice that of the (+)-enantiomer due to increased antitumor activity the enantiomers are equally toxic (139). The effectiveness of the DNA intercalator dmgs adriamycin [57-22-7] (195) and daunomycin [20830-81-3] (196) is affected by changes in stereochemistry within the aglycon portions of these compounds. Inversion of the carbohydrate C-1 stereocenter provides compounds without activity. The carbohydrate C-4 epimer of adriamycin, epimbicin [56420-45-2] is as potent as its parent molecule, but is significandy less toxic (139). 

Most of the physical properties (e.g., boiling and melting point, density, refractive index, etc.) of two enantiomers are identical. Importantly, however, the two enantiomers interact differently with polarized light. When plane polarized light interacts with a sample of chiral molecules, there is a measurable net rotation of the plane of polarization. Such molecules are said to be optically active. If the chiral compound causes the plane of polarization to rotate in a clockwise (positive) direction as viewed by an observer facing the beam, the compound is said to be dextrorotatory. An anticlockwise (negative) rotation is caused by a levorotatory compound. Dextrorotatory chiral compounds are often given the label d or ( + ) while levorotatory compounds are denoted by l or (—). 

Information regarding the fourth group is encoded in the new index by the fourth term t>at>bSc<3(1. When d is hydrogen, <5aSbScSd becomes zero otherwise it contributes to the RCI for the chiral center. 

Natarajan, R., Basak, S. C., Balaban, A. T., Klun, J. A., Schmidt, W. F. Chirality index, molecular overlay and biological activity of diastereoisomeric mosquito repellents. Pest. Manag. Sci. 2005, 61, 1193-1201. 

Symbolized by Q, the quality index is a parameter used in studying the stereochemical nature of a particular enzyme-catalyzed reaction using chiral [ O, 0, 0] phosphoric monoesters. This parameter, which is dependent on the fractional content, allows the investigator a means to assess the reliability of the study(ies). 

Note 3 Chiral nematic mesophases exhibit Bragg scattering of circularly polarised light at a wavelength proportional to the pitch P (Xr = P, where is the mean refractive index). 

The more active isomer (where activity refers to binding affinity at a defined receptor) is designated the eutomer, the less active is the distomer. The ratio of activities is the eudismic ratio, and its logarithm, the eudismic index, is then proportional to the difference in binding free energy between the enantiomers. The eudismic index is a quantitative measure of chiral discrimination. 

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