Stereochemical parameter

Table 8 Stereochemical Parameters for Some [M(unidentate)5] Complexes...

Table 9 Stereochemical Parameters for Some Octahedral Transition Metal Complexes, [M(unidentate...

Table 12 Stereochemical Parameters of Skew-trapezoidal Bipyramidal [Sn(bidentate)2R2] Complexes...

Table 13 Stereochemical Parameters of Bis(dithiochelate) Complexes of Selenium(II) and...

If the only way of obtaining the normalized bite of a bidentate ligand was from the crystal structure, the repulsion energy approach to stereochemistry would be limited. No matter how useful the theory may be in rationalizing the relation between different stereochemical parameters, it would have little predictive use since these other parameters are precisely determined at the... 

For two transaminases the remaining unknown stereochemical parameter was determined by demonstrating an internal transfer of tritium (dialkyl amino acid transaminase) [28] or deuterium (pyridoxamine-pyruvate transaminase) [27] from the a-position of the substrate L-alanine to C-4 of the cofactor. Internal hydrogen transfer from the a-position of the substrate amino acid to C-4 of PLP has also been demonstrated for two of the abortive transamination reactions, those catalyzed by tryptophan synthase fi2 protein [32] and by aspartate-/8-decarboxylase [31]. In addition, the same phenomenon must occur in alanine transaminase, as deduced from the observation that the enzyme catalyzes exchange of the /8-hydrogens of... 

Table 2 Stereochemical parameters for examples of [M(unidentate)5] complexes ...

Simon, Z., Ciubotariu, D. and Balaban, A.T. (1985b). Reactivity and Stereochemical Parameters in QSAR for Carcinogenic Polycyclic Hydrocarbon Derivates. In QSAR and Strategies in the Design in Bioactive Compounds (Seydel, J.K., ed.), VCH Verlagsgesellschaft, Weinheim (Germany), pp. 370-373. 

In the biomimetic chemical approach to biological systems, it is possible to estimate the relative importance of chemical and stereochemical parameters which contribute to the overall activity of the proteins. Thus, in the case of metalloproteins, it becomes possible to design superstructured models of the active site which lack a macromolecular peptide backbone but contain chemical groups involved in biological processes. 

Table 4 Stereochemical Parameters for Group V Halides, (MX3(lone pair)]...

The elucidation of the biochemistry of the vitamin D endocrine system has led to a renewed interest in the synthetic aspects of the field. Because of the limited availability of vitamin D metabolites from natural sources, the production of large quantities of metabolites and analogs is essential for detailed biomedical experimentation. Vitamin D analog synthesis has not only aided in determining the structural and stereochemical parameters of the natural metabolites, but has also helped to establish a foundation for structure-activity theories. 

The stereochemical parameters of these three low-spin species are presented in Table II. It can be seen, as in the five-coordinate intermediate-spin complexes, that there is significant variation in the parameters. The general decreases in Fe-Np and displacement follow the binding and ligand field strength of the axial ligand. A particularly noteworthy feature is the variation in the out-of-plane displacement of the low-spin iron(III) atom. 

M-NR, M-N adjacent and M-N trans to the N-substituent). The N-substituent is found on the side of the plane opposite the axial ligand and tends to block the sixth coordination site. Stereochemical parameters are summarized in Table VIII. A related nonmetalled complex is a N,N -dimethyletioporphyrin I species. The two methyl groups are on adjacent pyrrole rings but on opposite sides of the porphinato plane. 

These derivatives (Type B) are at least formally prepared by the insertion of a fragment into a M-N bond to yield a new M-X-N unit. Such species have been suggested as possible intermediates in the insertion of an oxygen atom into a G-H bond by cytochrome P-450. Several of these derivatives have formally had a carbene fragment inserted into a M-N bond. Such derivatives include a Ni derivative and a cobalt(III) species that has undergone two such insertion reactions. Other species represent the formal reaction of a vinylidene with iron(III) (two different crystalline forms). This iron derivative has an intermediate-spin state. Other complexes result from the insertion of a nitrene or an oxene This last derivative can also be considered to be a porphyrin N-oxide derivative and the structure of a free base species of a porphyrin N-oxide has also been reported". Appropriate stereochemical parameters for the members of this class are found in Table IX. 

Table VIII. Stereochemical parameters of N-substituted metalloderivatives ...

Table XII. Summary of stereochemical parameters of reduced porphyrin species ...

Table XIII. Stereochemical parameters of thallium and indium complexes ...

Stereochemical parameters have been very briefly reported for Rh(TPP)(C6H5)Cl and recently the crystal structures of Mo(TPP)(QH5)Cl and Ge(MGP)(CH3)2 have been described where MGP = dimethyl-5,10,15,20-tetrakis[3, 5 -bis(l",l"-dimethyl-ethyl)phenyl] porphyrinato. 

---