Isomers, structure—activity

Much remains to be accomplished in the separation, isolation, and identification of both naturally occurring and synthetic bioactive materials effective in the germination of parasitic weed seeds. Structure-activity studies suffer from the lack of separation of isomers in most synthetic samples. Strigol is an important tool in basic studies on the effect of chemicals on seed germination, but it is highly unlikely that the compound will meet practical field... 

There are two asymmetric carbon atoms and E, Z-isomers in norchrysanthemic acid. So, there exist eight stereoisomers. In order to elucidate the structure activity relationship of metofluthrin stereoisomers, we investigated the synthetic pathways of all stereoisomers of norchrysanthemic acid. 

LSD (4.126) is a rather structure-specific compound. Only the (+)-isomer is active, and alkylamides other than the diethyl derivative, including some cyclic analogs (the pyrro-lidide and morpholide analogs), have very low activity. Lysergic acid does contain the... 

More recendy the cis and trans isomers of the mosquito repellent CIC-4, a mixture of citronella isomers, have been separated by preparative hplc and bioassayed for effectiveness (23). Chiral-phase capillary gas chromatography and mosquito repellent activity of some oxazolidine derivatives of (+)-and (— )-citronellal have been studied to find structure—activity relationships (24). Several 2-alkyl- -acetyloxalidines have been synthesized and tested against mosquitoes, with further efforts using nmr to determine the rotational isomers of the more active N-acetyl-2,2-dimethyloxazolidine (25). 

SCH 50971 (22) and SCH 50972 (23)) which carry the methyl substituent in the 4-position that is tram orientated to the imidazole residue, exhibit a structure-activity relationship similar to that of the trans-2-isomers 20 and 21. Again the dextrorotatory (3i ,4/ )-enantiomer SCH 50971 (22) proved to be the eutomer being more than 10-fold more potent than the corresponding (3S,4S)-antipode SCH 50972 (23) [23],... 

White R, Malpass JR, Handa S, Baker SR, Broad LM, Folly L, Mogg A (2006) Epibatidine Isomers and Analogues Structure-Activity Relationships. Bioorg Med Chem Lett 16 5493... 

To the Court this was an important admission as it rebutted an earlier assertion by the inventor s representatives that structure-activity relationship principles would have completely discouraged skilled artisans from preparing the separate isomers of the racemic mixture (ofloxacin) or from reasonably expecting that one enantiomer would exhibit greater activity than the racemic mixture. The publication also indicated that... 

Numerous studies have examined the structure-toxicity relationships for CDDs. For example, examination of lethality data in guinea pigs revealed that the fully lateral-substituted tetra- to hexachloro-substituted isomers were the most toxic congeners, and the structure-activity relationships were comparable to those observed for their AHH-induction and receptor-binding activities (Eadon et al. 

The //v7/ -t -isomerization of 3-chlorothietane-l-oxide 2a has been studied using ab initio methods <2001JMT235>, where for the prediction of this system s thermodynamics, the M0ller-Plesset perturbation theory has been used. The calculation predicted that in the gas phase the cA-isomer was predominantly present, reaching 85%, and that in solution of polar and nonpolar solvents the concentration of the zA-isomer decreased to 25%. Similar results have been found for 3-methylthietane-l-oxide 2b. For both compounds, transition states have been found to have a quasi-planar structure. Activation energies for compounds 2a and 2b have been computed and they were 49 and 45kcalmol 1 in the gas phase as well as 37 and 33 kcal mol 1 in solution, respectively. For... 

The importance of resolution and determination of absolute configuration cannot be overemphasized. There was, in this writer s opinion, little significant progress in developing useful receptor models prior to the determination of the absolute configurations for the active enantiomers of apomorphine, I, certain N-substituted 5-hydroxy-2-amino-l,2,3,4-tetrahydronaphthalenes, and of 6,7-ADTN (X). It is very common to see structures drawn in the literature with their chiral center shown as a particular absolute configuration, for example similar to that of apomorphine. Yet, in many of these cases there is no evidence as to which isomer is active. The reversed stereochemistry for the active enantiomers of apomorphine and... 

A central question in phosphotransferases and nucleotidyltransferases is the structure of the metal-nucleotide complex which is the true substrate for the enzyme. It is unlikely that all of the possible Mg-ATP complexes could serve as substrates for a given enzyme, but until recently there has been no way to determine which isomer is active. The difficulty is the coordination exchange equilibrium, which is rapidly set up and dynamically maintained in solutions of Mg-ATP. To avoid this problem, metal-nucleotide complexes have been synthesized using coordination exchange-inert metals such as Cr(III) and Co(IIl) in place of Mg(II) [7,60], The resulting complexes are structurally stable and can be separated by chromatographic methods into their coordination isomers and stereoisomers. The isomers can then be investigated as substrates or inhibitors of specific enzymes. 

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