The dicatechol ester ligand 2-H4 forms the compressed helicate Li4[(2)3 Ti2] which upon removal of internally bound lithium cations expands. In form, chiral diol units control stereochemistry complex is lost expansion system.

the results of mndo, am1 and pm3 semi-empirical calculations and hf/6-31g*, mp/6-31g*, mp2/6-311+g**, and b3lyp/6-311g** and qcisd/6-31g* ab initio methods for angle strain and conjugation effects in twist-boat, boat, and half-chair geometries of (z,z,z)-cycloocta-1,3,5-triene indicate that all methods, except pm3, predict wrong ordering of the conformations.

ab initio calculations at hf/6-31g* level of theory for geometry optimization and mp2/6-31g*//hf/6-31g*for total energy calculation are reported for z-cyclooctene (1). the most favorable conformation of 1 is theunsymmetric boat-chair (1-bc) geometry. potential energy profiles for two different boat-chair/boat-chairinterconversion processes were calculated. the process via a chair transition sta...

The epimerization of avoparcin entities is discussed in some detail. The absolute stereochemistry of avoparcin is now known since the N-methyl terminal amino acid of the aglycone has been isolated and shown to exhibit negative optical rotation and hence has the R-configuration. The same amino acid has been isolated from an epimerized solution of avoparcin and found to have positive rotation and...

An approach to the determination of the complete stereochemistry of enzymatic transamination is described. Stereospecificity in the enzymatic labilization of one of the 4-methylene protons of pyridoxamine has been demonstrated in the transamination of pyridoxamine catalyzed by apoglutamate-oxaloacetate transaminase. Both enantiomers of the 4-(CHD-NH2) pyridoxamine have been prepared. These comp...

A change of solvent causes an inversion of the stereochemistry at copper of the chiral Cu(I) complex described herein.

The CD exciton chirality method was applied to determine the absolute stereochemistry of the strevertenes, antifungal pentaene macrolides produced by Streptoverticillium sp. LL-30F848. The CD difference spectrum of strevertene A methyl ester 15-dimethylaminobenzoate showed a positive couplet between the dimethylaminobenzoate and the pentaene chromophores, and therefore established the 15R confi...

Stereoselectively labeled samples of E—2an Z—[9—2H,3H]— chorismate have been synthesized from Fand z-[3H, Hlphosphoen6lpyruvate by the enzymes of the shikimate pathway. The position of the tritium label at the 9—position of chorismate has been determined, from which it is evident that in the reaction catalyzed by 3-phosphoshikimate 1—carboxyvinyltransferase, the addition step has the opposite s...

In this research, Quantum-mechanical calculations were performed at the HF method with the 6-31+G*basis set and at the B3LYP method with the 6-31+G* basis set in the gas phase and five solvents such as water, DMSO, methanol, ethanol and dichloromethane at six temperatures. According to these theoretical results of IR, we extracted thermo chemical parameters such as enthalpy (∆H Kcal/mol), Gibbs...