Cahn-Ingold-Prelog descriptors

Figure 4. Assignment of a Cahn-Ingold-Prelog descriptor...

Specifies unusual valencies Specifies isotopes Describes stereoconfiguration Cahn-Ingold-Prelog descriptors Cahn-Ingold-Prelog descriptors Specifies Tree-site attachment in substructures... 

The S in S adenosylmethio nine indicates that the adenosyl group is bonded to sulfur It does not stand for the Cahn-Ingold-Prelog stereochemical descriptor... 

Three-dimensional (3-D) descriptors of molecules quantify their shape, size, and other structural characteristics which arise out of the 3-D disposition and orientation of atoms and functional groups of molecules in space. A special class of 3-D indices is quantitative descriptors of chirality. If a molecule has one or more chiral centers, the spatial disposition of atoms can produce enantiomers, many of which will have the same magnitude of calculated and experimental physicochemical properties having, at the same time, distinct bioactivity profiles. Basak and coworkers [22] have developed quantitative chirality indices to discriminate such isomers according to their structural invariants which are based on the Cahn-Ingold-Prelog (CIP) rules. 

There are many procedures to determine the chirality sense of a stereomodcl, the best known being the R and S descriptors of the Cahn-Ingold Prelog (CIP) system. 

The steering-wheel-convention is customized for monodentate coordination polyhe-dra and is similar to the Cahn-Ingold-Prelog system, whereby priorities are assigned to substituents on stereogenic centers. Instead of R/S descriptors, C (clockwise) and A (anti-clockwise) descriptors are introduced... 

Give the Cahn-Ingold-Prelog R and S descriptors for the diol(s) formed from cis-2-pentene and fran5 -2-pentene on treatment with the osmium tetraoxide/tert-butyl hydroperoxide reagent. 

CIP (Cahn, Ingold, Prelog) method, CIP system The CIP sequencing rules establish the conventional ordering of ligands for the unambiguous description of absolute configuration by descriptors such as R, S P, M E, Z. 

Chirality may exist in many molecules that do not possess a chiral center. Such compounds may possess a chiral plane or a chiral axis, and are said to be dissymetric with respect to either that plane or that axis. Certain optically active allenes, biaryls, alkylidenecyclohexanes, and spiranes provide examples of axially dissymmetric molecules (chiral axis), irons-Cycloalkenes exemplify planar dissymmetry in molecules. The configurations of these classes may be specified by the Cahn-Ingold-Prelog convention using the usual R and 5 descriptors. Special subrules, which we will not describe here, are applied to this purpose. The interested reader is referred to references 8 (see p. 43) and 9 for details. Scheme 2.1 presents some molecules that are optically active because of planar or axial dissymmetry, and for which the absolute configurations have been determined. 

The chirality, or handedness, of a molecule is described by specifying its configuration. The system that has received general acceptance is the Cahn-Ingold-Prelog convention, which uses the descriptors R and 5. The Fischer convention. 

A. If the side chain of the amino acid is a methyl group, the compound is referred to as alanine. What is the Cahn-Ingold-Prelog stereochemical descriptor for the chiral center in alanine ... 

---