X-phenoxyacetic acids

The earliest successful biological QSAR correlating plant growth regulating activity of X-phenoxyacetic acids utilized Hammett sigma constants for electronic effects and pi-constants for hydrophobicity. Pi (designated by lower case Tt) for the most common substituents was taken as the difference in the... 

The addition of suitable precursors (e.g., phenylacetic acid, phenoxyacetic acid) in the fermentation medium of P. chrysogenum allows the formation of specific penicillins (G, V, F, K, X) with nonpolar side chains < 1995JAN1195, 1998MI2001, 1999MI173>. Penicillins are the only /3-lactam products formed, while fermentation of Cephalosporium acremonium produces penicillin N (D-a-aminoadipyl side chain) together with cephalosporin derivatives (CHEC-11(1996), section 1.20.6.1) <1996CHEC-II(1B)623>. 

Model Parent Compound Series. Experimental partition coefficient data for a variety of substituted benzenes and seven other related parent compound series (phenoxyacetic acid, phenylacetic acid, benzoic acid, benzyl alcohol, phenol, aniline, nitrobenzene) were reported in 1964 by Fujita et al. (II). The ir values (see Equation 3) derived for individual substituents in each of the above-mentioned parent compound series have since been frequently used (with varying degrees of success) by many investigators to approximate tt values for the corresponding substituents in other related parent compounds for which no experimental partitioning data are available. For example, Hansch and Deutsch (26), in a correlation study of structure—activity relationships in cholinesterase inhibitors, used tr values derived for aromatic ring substituents (X) in the phenoxyacetic acid series... 

Partition coefficients are of extreme value in medicinal chemistry as they may be related to drug transfer across membranes and binding at active centres. The parameter logP models various kinds of transport between aqueous and lipid phases and P is defined as the partition coefficient of a substance between water and n-octanol. The free energy of the transport process is often linearly related to standard hydro-phobic parameters (re) for substituents (X) determined from Px values for substituted phenoxyacetic acids and that for the parent acid Ph (Equation 16). 

The substituent X has a tr value defined from the partitioning of substituted phenoxyacetic acids between n-octanol and water. Thus tt for the parent (x = H) is defined as zero. Both w and log P (Table 17) may be used as parameters, the former in a restricted series of substituted phenyl groups and the latter in more general correlations. 

Trillas, M., Pujol, M. and Domenech, X., 1996, Photocatalyzed degradation of phenol, 2,4-dichlorophenol, phenoxyacetic acid and 2,4-dichlorophenoxyacetic acid over supported TiOz in a flow system. J. Chem. Tech. Biotech., 67(3) 237-242. 

Figure 5.1. Relationship between pKg values of substituted benzoic acids and their equivalent acetic acid and phenoxyacetic acid derivatives, o = o-substituted benzoic acids against o-substituted phenoxyacetic acids, x = m- and p-substituted benzoic acids against the corresponding phenoxyacetic acids. = p-substituted benzoic acids against a-substituted acetic acids.

Lovenberg, Buchanan, and Rabinowitz (65) tested the response of ferredoxin to mercury compounds. Two mercurial reagents used, p-mer-curibenzoate (PCMB) and o-((3-hydroxymercuri-2-methoxypropyl)car-bamyl)phenoxyacetate (sodium mersalyl) reacted rapidly with ferredoxin and caused a bleaching of the visible spectrum and a concomitant loss of biological activity. C. pasteurianum ferredoxin was titrated with PCMB as described by Boyer (24) and the results showed that 20 moles of PCMB reacted with 1 mole of ferredoxin. In another determination, 2 moles of PCMB reacted with 1 mole of sodium sulfide. Since ferredoxin contained 7 moles of inorganic sulfide and 8 moles of half-cystine residues, 22 (7 x 2 = 14 14 + 8 = 22) moles of PCMB would be expected to react with 1 mole of ferredoxin. These data, summarized in Table 8, are consistent with the existence of two types of sulfur in ferredoxin. This conclusion was supported by the presence of half-cystine residues in ferredoxin after inorganic sulfide had been removed by acid hydrolysis, as well as results of sulfur analyses, which showed an amount of sulfur greater than could be attributed to half-cystine residues. 

---