3- Methoxyphenoxyacetic acid

The activity of methoxyphenoxyacetic acids with 4-allyl and 4-isoaiIyl substituents increases compared to the parent compounds, but they exhibit definite antiauxin action. 

A number of other useful highly acid-labile handles are also available. Most of these linkers are formed by introducing electron-donating substituents into the benzyl groups that serve as the peptide-resin anchor. The first handle of this type, 4-hydroxymethyl-3-methoxyphenoxyacetic acid (HMPA), 3, was introduced by Sheppard and Williams [22,23]. A closely related and more widely used alternative is 4-(4-hydroxymethyl-3-methoxyphenoxy) butyric acid [24-26] (HMPB), 4. 

Figure 22 GC chromatogram of TMAH intrainjector derivatized phenoxy acids. Peaks 1 =2-phenoxypropionic acid 2=p-fluor-ophenoxyacetic acid 3=2-methylphenoxyacelic acid 4=3-me-thylphenoxyacetic acid 5=4-melhylphenoxyacetic acid 6= 2-formylphenoxyacetic acid 7=2,5-dimethylphenoxyacetic acid 8=2-(4-chlorophenoxy)propionic acid 9=2,4-dimethylphenoxy-acetic acid 10=2-methoxyphenoxyace1ic acid 11=4-phenox-ybutyric acid 12=3-melhoxyphenoxyacetic acid 13= 4-methoxyphenoxyacetic acid 14=2-(4-chloro-2-methyl-phenoxy)propionic acid 15 = 4-chloro-2-methylphenoxyacetic acid 16 = 2,4-dichlorophenoxypropionic acid 17 = iodophenoxy-xyacetic acid 18 = a-(2,4,5-trichlorophenoxy)propionic acid 19 = 2,4,5- trichlorophenoxyacetic acid. (Reproduced with permission from Brondz I and Olsen I (1992) Intra-injector formation of methyl esters from phenoxy acid pesticides. Journal of Chro-matogreiphy 598 309-312.)...

The advantages of using triphase catalytic reaction are that it easily recovers the catalyst and purifies the product and reactant. Hence, Ae reuse, stability and degradation of the catalyst must always be considered. Resins with onium groiqis may be used for extended periods or repeated cycles only if the catalyzed reactions occur under sufficiently mild conditions to avoid degradation. The number of active site maintained constant up to SO, and then decreased dramatically as the temperature increased (Table 2). Figure 2 shows the relationship of the yield of 4-methoxyphenoxyacetic acid butyl ester and the reaction time for the reuse of resin. The reactivity of the reuse resin was lower than that of the resin for first reaction. 

Fig 2 Plot of yield of 4-methoxyphenoxyacetic acid butyl ester on the reaetion time. Resin (45- 60mesh) = 1.5g, KOH(7M)=50 cm CH3OCH6H4CH2COOH = 0.03mol, 1-Br(C4H9) = 0.073 mol. 

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