Chiral compounds 1728 INDEX

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 (—). 

Because the trend shown above continues, we can conclude that the C sequence dominates L, or alternatively that C is more chiral than L. Observe that the conclusion is based on ordering of structures, not on the numerical value of an index. When this analysis is extended to all 28 chiral compounds of Figure 34, we obtain the partial ordering shown in Figure 35. 

The Naming of Chiral Drugs. The nomenclature of chiral compounds is difficult and sometimes confusing. We have already introduced the prefixes R and S, (- -) and (—), and D and L. We have already seen many common names for drugs that have an implied chirality, as in methamphet-amine and ephedrine. The hyphenated prefixes R/S, D/L, and + / — render the alphabetic indexing of pharmaceutics problematic. One approach to this problem that has been used to help with this issue is to select drug names where the chirality has been imbedded into the common chemical name. One example that we have discussed is esomeprazole,... 

While polarimetric detectors usually use fight sources in the visible-near IR region, OR and CD detectors use ultraviolet (UV) lamps. The sensitivity of the former is appropi-ate for the detection of sugars, but it is very low for many other chiral compounds (dmgs and synthetic intermediates, for instance). As a result, polarimetric detection is less and less used. As refractive index (Rl) detectors, OR detectors are broadly applicable. They do not require a chromophore... 

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). 

Prior to the 14th Collective Index, registry numbers were assigned to the (+/-)-forms (racemic mixtures) of compounds with one chiral centre. From the 14th Collective Index onward these assignments... 

A word of caution should be added with respect to Chemical Abstracts, as far as chirality assignments of homoannular substituted ferrocene derivatives are concerned. Until the 8th collective index, only (-f) and (—) are found as chirality indicators. For quite a long time, no descriptors were given at all, only the remark stereoisomer , followed by the registry number, which does not allow identification of a compound easily. This fact is in sharp contrast to the claims of Chemical Abstracts Service authors that they would consequently use Schlogl s central descriptors [20, 21]. Since volume 114, the (R, S ) nomenclature for ferrocene derivatives begins to appear, but its application is not very consequent, at least at the time where the book was written, and it is advisible to examine the orginal article rather than trust Chemical Abstract s descriptors. 

Abstract Enantioselective heterogeneous catalysis requires surfaces with structures that are chiral at the atomic level. It is possible to obtain naturally chiral surfaces from crystalline inorganic materials with chiral bulk structures. It is also possible to create naturally chiral surfaces from achiral materials by exposing surfaces that have atomic stractures with no mirror symmetry planes oriented perpendicular to the surface. Over the past decade there have been a number of experimental and theoretical demonstrations of the enantiospecific physical phenomena and surface chemistry that arise from the adsorption of chiral organic compounds on the naturally chiral, high Miller index places of metals. 

Example 4 shows the compound [CoBr2(en)(NH3)2]+ which has the polyhedral symbol OC-6 and the configuration index 32. The chirality symbol is C. 

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