The resolution of [Tris{cis-Diydroxybisethylene Diaminecobalt(III)}cobalt(III)] Nitrate

1958 ◽  
Vol 11 (4) ◽  
pp. 426 ◽  
Author(s):  
H Goodwin ◽  
EC Gyarfas ◽  
DP Mellor
Keyword(s):  
Optically Active ◽  
Optical Isomers

The resolution of [tris{cis-dihydroxybisethylenediaminecobalt(II)}cobalt(III)] nitrate (hexol nitrate) into four of the eight theoretically possible optical isomers using potassium d- and l-antimonyl tartrate is described. The reactions involved in the formation of the optically active isomers of the hexol ion show less stereospecificity than those of similar complexes studied by earlier investigators.

scholarly journals Comparative studies of the specificities of α-chymotrypsin and subtilisin BPN′. Studies with flexible and ‘locked’ substrates

1972 ◽  
Vol 126 (3) ◽  
pp. 659-665 ◽  
Author(s):  
T. N. Pattabiraman ◽  
W. B. Lawson
Keyword(s):  
Methyl Ester ◽  
Carbon Atom ◽  
Binding Site ◽  
Comparative Studies ◽  
Detrimental Effect ◽  
Optically Active ◽  
The Other ◽  
Optical Isomers ◽  
Polar Groups ◽  
Hydrolysis Of

Subtilisin BPN′ hydrolysed N-acetyl-l-3-(2-naphthyl)-alanine methyl ester, N-acetyl-l-leucine methyl ester and N-acetyl-l-valine methyl ester, faster than α-chymotrypsin. Of eight ‘locked’ substrates tested, only methyl 5,6-benzindan-2-carboxylate was hydrolysed faster by subtilisin, whereas the other esters were better substrates for chymotrypsin. Compared with the values for chymotrypsin, the stereospecific ratios during the hydrolysis of the optically active locked substrates by subtilisin were decreased by one and two orders of magnitude for bi- and tri-cyclic substrates respectively. The polar groups adjacent to the α-carbon atom of locked substrates did not contribute significantly to the reactivity of the more active optical isomers, but had a detrimental effect on the less active antipodes during hydrolysis by both the enzymes. These studies show that the binding site of subtilisin BPN′ is longer and broader than that of α-chymotrypsin.

The Role of Chirality in the Activity of Photosystem II Herbicides

1987 ◽  
Vol 42 (6) ◽  
pp. 663-669 ◽  
Author(s):  
Gary Gardner ◽  
James R. Sanborn
Keyword(s):  
Photosystem Ii ◽  
Biological Activities ◽  
Critical Role ◽  
Optically Active ◽  
Chiral Discrimination ◽  
In Vitro Assays ◽  
Optical Isomers ◽  
Steric Factors

Although significant differences in activity between optical isomers have been recognized in many types of pesticides, the role of stereoselectivity has not been fully characterized for one of the most important classes of commercial herbicides, those that inhibit photosynthetic electron transport. This report describes experiments in which optically active α-methylbenzylamine or sec-butylamine was used as starting material for the synthesis of optically active triazine and urea herbicides. The biological activities of the compounds were determined in two in vitro chloroplast assays - competition for specifically bound [14C]atrazine and inhibition of photosystem II-medi- ated dye reduction - as well as in whole plant phytotoxicity. In both in vitro assays the (-)-isomer of the N-a-methylbenzyl triazine was about 15-fold more active than the (+)-isomer, and the racemate fell in between and was of about the same potency as atrazine. The same relative activities were also seen for in vivo phytotoxicity. The a-methylbenzyl urea derivatives were much less herbicidally active, but the in vitro assays were able to discriminate between the optical isomers. In both assays, the (-)-isomer of the urea was much more active than the (+)-isomer, with the racemate intermediate. Steric factors play a critical role in the degree of this chiral discrimination, since in both the corresponding triazines and ureas, the optically active molecules synthesized from the enantiomers of 2-butylamine showed only slight differences in activity. Saturation of the phenyl ring of the a-methylbenzyl triazines resulted in molecules which still showed substantial differences in activity related to chirality, further supporting the importance of steric factors, rather than electronic, in this chiral discrimination.

Bis-1,10-phenanthroline complexes of divalent ruthenium

1966 ◽  
Vol 19 (12) ◽  
pp. 2229 ◽  
Author(s):  
B Bosnich ◽  
FP Dwyer
Keyword(s):  
Ruthenium Complexes ◽  
Optically Active ◽  
Optical Isomers

A series of divalent ruthenium complexes of the type cis-[RuX phen2 py]2+ (phen = 1,10-phenanthroline, py = pyridine, X = py, Cl, Br, I, N3, NCS, NO2, CN, NH3, CH3CN), have been isolated and characterized. The cation cis-[Ru phen2 py2]2+ has been resolved into its optical isomers from which the optically active monosubstituted complexes have been prepared.

Resolution of 4-aminoflavan into its optical isomers; nuclear magnetic resonance spectra of 4-aminoflavan and 3-aminoflavanone derivatives

1970 ◽  
Vol 23 (10) ◽  
pp. 2015 ◽  
Author(s):  
R Bognar ◽  
JW Clark-Lewis ◽  
A Liptakne-Tokes ◽  
M Rakosi
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Fractional Crystallization ◽  
Catalytic Hydrogenation ◽  
Optically Active ◽  
Sulphonic Acid ◽  
Trans Configuration ◽  
Optical Isomers ◽  
Nuclear Magnetic Resonance Spectra ◽  
Magnetic Resonance Spectra

(�)-2,4-cis-4-Aminoflavan obtained by reduction of 4-oximinoflavan has been resolved into enantiomeric forms by fractional crystallization of its amine salts with (+)-camphor-10-sulphonic acid and with (-)-di-O-benzoyltartaric acid. The pairs of diastereoisomeric salts thus separated were converted into (+)- and (-)-2,4-cis-4-aminoflavan hydrochlorides, from which the free bases and the optically active N-acetyl and N-benzoyl derivatives were prepared. N.m.r. data unequivocally establish the 2,4-cis configuration of all these 4-substituted flavan derivatives. 3-Aminoflavanone prepared by the Neber rearrangement of 4-oximinoflavan, and also by controlled catalytic hydrogenation of 3-oximinoflavanone, is shown from N.M.R. data on suitable derivatives to have the 2,3-trans configuration.

scholarly journals Chiral Shielding in Nuclear Magnetic Resonance Spectroscopy

1979 ◽  
Vol 32 (6) ◽  
pp. 1375
Author(s):  
PJ Stiles
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Resonance Spectroscopy ◽  
Nuclear Magnetic Resonance Spectroscopy ◽  
Active Species ◽  
Optically Active ◽  
Magnetic Shielding ◽  
Resonance Spectroscopy ◽  
Optical Isomers ◽  
Chiral Species

A novel van der Waals shielding mechanism is discussed which contributes to the magnetic shielding non-equivalence of optical isomers of one chiral species in the presence of a second optically active species. It is more direct than standard mechanisms which invoke stereospecific association of the interacting molecules but appears to be of marginal experimental significance.

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