Carboxylic acids, functional derivatives

The next several chapters deal with the chemistry of various oxygen-containing functional groups. The interplay of these important classes of compounds—alcohols, ethers, aldehydes, ketones, carboxylic acids, and derivatives of carboxylic acids— is fundfflnental to organic chemistry and biochemistry. 

The transformation of the hydrophobic periphery composed of bromo substituents into a hydrophilic wrapping of carboxylic acid functions was achieved by reacting 31 with (i) n-butyllithium and (ii) carbon dioxide. The polymer-analogous transformation provides water soluble, amphiphilic derivatives of 31 which constitute useful covalently bonded unimolecular models for micellar structures. 

The transformation of the terminal bromo substituents to carboxylic acid functions with (i) n-butyl lithium (ii) carbon dioxide, provides water soluble derivatives of 47 which are interesting as models for unimolecular micelles. 

Silyl-derived linker 36 was prepared in three steps from a silyl ether of serine and incorporated for Fmoc/tBu-based assembly of protected gly-copeptide blocks (Scheme 11) [42]. The a-carboxylic acid function of serine was protected as an allyl ester. Deprotection by a Pd(0) catalyst in the presence of dimedone liberated the carboxylic acid in order for subsequent... 

With regard to carboxylic derivatives, there is generally little difference in chemical shift among the various trifluoroacetic acid derivatives, as exemplified by the examples in Scheme 5.25. Also, the effect of moving the CF3 farther from the carboxylic acid function is similar... 

Complexone-like derivatives. Cyclic systems containing attached carboxylic acid functions such as (105) and (106) have been synthesized. 

E. Jacobson in 1882 fused phthalic anhydride with quinoline bases obtained from coal tar, which also contained quinaldine (136). He thus received quinophthalone (137). Quinophthalone derivatives bearing sulfonic or carboxylic acid functions represent suitable anionic dyes. Derivatives carrying basic side chains containing quarternary nitrogen, on the other hand, provide cationic dyes. The compounds are used especially as disperse dyes [1]. 

The most simple way to introduce carboxylic acid functionalities onto hyperbranched polyesteramides is to modify the hydroxyl functions with suitable diacid derivatives. The modification can either be done in melt or in solution. 

The main fluorescent pH indicator probes are based on fluorescein and therefore it is important to understand the pH-dependent ionic equilibria of it and its derivatives, hi aqueous solutions above pH 9 the phenolic and carboxylic acid functional groups in the molecule are almost totally ionised (Figure 3.14). Upon acidification of the dianion, firstly, protonation of the phenolic group occurs (pK 6.4) to yield the monoanion followed by the carboxylic acid (pA < 5), giving the neutral species of fluorescein. On further acidification the fluorescein cation pK 2.1) is generated. In strongly acidic environments fluorescein is non-fluorescent, only the mono-anion and di-anions are fluorescent, with quantum yields of 0.37 and 0.93, respectively. The pH-dependent absorption spectrum of fluorescein exhibits a blue-shift and... 

Dithiin, 1,4-benzodioxin, and its 2-substituted derivatives can be readly deprotonated and trapped with electrophiles although the reaction is more problematic with 1,4-dioxin. Oxanthrene and phenoxathiin are cleaved with lithium <1996CHEC-II(6)447>. A more recent example deals with the metallation at C-3 of the 1,4-benzodioxane 60 bearing a carboxylic acid function at C-2, with lithium diisopropylamide (EDA) and subsequent quench with iodomethane. The corresponding 3-methylated benzodioxane 61 was isolated in 70% yield (Equation 6) <2000EJM663>. 

The use by Langlois of an amidoalcohol (79,80) is an unusual strategy for the construction of a-amino acids. More commonly, the required amine and carboxylic acid functionalities are carried into the cycloaddition in the dipolarophile, as a homochiral alkenyl a-amino acid derivative. Importantly, this introduces a second... 

Acrylic Acid Propenoic Acid Benzoic Acid Carboxylic Acids Carboxylic Acids and Derivatives Carboxylic Acids with Other Functional Groups Carboxylic Acids with Other Functional Groups Dichlorophenoxyacetic Acid 2,4-d Cesium... 

In an effort to explore the chemistry of pyrrolodiazines and their quatemized salts (see Section 6.2.2.2), Alvarez-Builla and co-workers prepared a series of pyrrolo[l,2-c]pyrimidines via methodology developed in their laboratory <99JOC7788>. Cyclocondensation of tosylmethyl isocyanide with substituted pyrrole-2-carboxaldehydes 17 produced pyrimidine derivatives 18 sifter removal of the tosyl group. The key to this procedure was the use of tosylmethyl isocyanide, which provided a relatively easily removed tosyl group in comparison to the more problematic decarboxylation of a carboxylic acid functionality. 

Several derivatives have been prepared by acid-catalyzed cyclization of 4-hydrazinopyridines containing a carboxylic acid function. For example, cyclization in dilute acids of 130125 or 131a (R = H, Ar)19,126-128 gave the 3-hydroxypyrazolo[4,3-c]pyridines 132 (R1 = Ar, R2 = H) or N-oxides 133... 

The taurine residue can also be found as an amide derivative of the 26-carboxylic acid function in the 3p,5a,6p,15a-polyhydroxylated steroids 328 and 329, which were obtained from the starfish Myxoderma platyacanthum [245]. The structures of both compounds were determined from spectral data and chemical correlations. The bile of the sunfish Mola mola has been shown to contain a new bile acid conjugated with taurine (330) together with sodium taurocholate. Compound 330 was identified as sodium 2-[3a,7a, 11 a-trihydroxy-24-oxo-5P-cholan-24-yl]amino]ethane-sulfonate on the basis of its physicochemical data and chemical transformations [246]. 

Closely related to these compounds are the carolisterols A-C (331-333), which were isolated from deep-water starfish Styracaster caroli [247]. Carolisterols A-C are characterized by a polyhydroxycholanic acid moiety in which the 24-carboxylic acid function is found as an amide derivative of D-cysteinolic acid. Z)-cysteinolic acid has been found in fish, alga, and other marine organisms [248]. 

By this definition, an amide, RCONH2, but not a ketone, RCOCH3, is a functional derivative of a carboxylic acid. Several derivatives of carboxylic acids are given in Table 18-3, and methods for preparation of these derivatives are summarized in Tables 18-6 and 18-7 at the end of the chapter. 

Succinate esters serve as examples of derivatives that exhibit less than optimal pH-hydrolysis rate behavior owing to their increased reactivity in water as a result of intramolecular catalysis of hydrolysis by the terminal carboxylic acid functionality (Anderson and Taphouse, 1981 Anderson etal., 1984 Damen etal., 2000). Since intramolecular catalytic effects are quite sensitive to geometric factors and distances separating the interactive groups (Anderson and Conradi, 1987), intramolecular catalysis by a terminal ionizable group should be easily controlled by varying the alkyl chain length. 

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