dM-Dim for carboxylic acid protection

The 1,3-dithian-2-yl-methyl (Dim) and its analogous groups including dimethyl-Dim (dM-Dim) can provide a new dimension of orthogonality for carboxylic acid protection. They can be deprotected under nearly neutral oxidative conditions. In this paper, the protection of carboxylic acid with dM-Dim, deprotection of dM-Dim ester with sodium periodate, stability of dM-Dim protected carboxylic acid under acidic and basic conditions, and selective deprotection of dM-Dim protected carboxylic acids in the presence of tertiary butyl and methyl esters are presented.     

Fe-catalyzed thioesterification of carboxylic esters

Second nature: Starting from shelf-stable aryl esters and thiols, a variety of carboxylic acid esters were transformed into the corresponding thioesters with no racemization of labile stereocenters. The method was successfully applied in a native chemical-ligation-type peptide formation, which suggests that the thiol may act as a co-catalyst for future 1,2-additions of pronucleophiles to carboxylic esters.     

Urea-tetrahydrobenzoxanthene receptors for carboxylic acids

Hydrogen-bonding receptors for carboxylic acids have been prepared based on a cis tetrahydrobenzoxanthene skeleton. X-ray diffraction study of one of these compounds revealed that the cleft is suitable for establishing strong linear hydrogen bonds with the oxygen of a water molecule. Complexes that set only three H-bonds with the guests showed no chiral recognition with amino acid derivatives. However, suitable functionalization of the receptor provided a fourth H-bond with certain amino acid derivatives, leading to significant enantioselective complexation in this case.     

Esterification of polymeric carboxylic acids

Polymers containing pendant carboxyl groups have been essentially completely esterified with little apparent change in molecular weight by the use of one of the following reagents: (1) trialkyl orthoesters, (2) dimethylformamide dialkyl acetals, (3) tertiary amines followed by alkyl halides, (4) quaternary ammonium hydroxide followed by alkyl halides. The use of some of these methods permits preparation of certain polymers that were previously not readily accessible.     

Iron-catalysed green synthesis of carboxylic esters by the intermolecular addition of carboxylic acids to alkenes

Iron triflate, in situ-formed from FeCl3 and triflic acid, or FeCl3 and silver triflate efficiently catalyse the intermolecular addition of carboxylic acids to various alkenes to yield carboxylic esters; the reaction is applicable to the synthesis of unstable esters, such as acrylates.     

Measurement of the reactive and available solid-supported carboxylic,N-hydroxysuccinylated carboxylic,and aldehydo groups

We describe new colorimetric methods for the determination of the reactive and available solid-supported carboxylic,N-hydroxysuc cinylated carboxylic, and aldehydo groups under conditions usually applied for the coupling of biomolecules. The methods involve the reaction of the solid-supported functional groups with tyramine or cysteine, and the subsequent titration of the ligand coupled onto the solid supports using the commercially available bicinchoninic acid/copper protein assay reagent (BCA). The titration is based on the ability of these ligands to reduce Cu²⁺ to Cu⁺, which forms a chelate complex with bicinchoninic acid absorbing at 562 nm. The quantita tion is finally carried out through standard curves obtained using tyramine or cysteine solutions of known concentrations. The values obtained by the assays developed for several solid supports carrying carboxylic, NHS-ester, and aldehydo groups were well correlated with those obtained by other literature methods or provided by the manu facturers. All of the proposed methods are simple, more sensitive than other relevant literature methods, and require only commericially available reagents.     

Solvent-free biocatalytic amidation of carboxylic acids

Lipase-catalyzed enantioselective amidation was performed by reacting the racemic amine with aliphatic acids in nonsolvent system. The reaction equilibrium was shifted towards amide synthesis by the removal of water under reduced pressure. This methodology avoids the use of activating agents and hazardous solvents.     

Silver-catalyzed decarboxylative halogenation of carboxylic acids

Decarboxylative halogenation of carboxylic acids catalyzed by silver carbonate is reported. ortho-Nitrobenzoic acids react with copper(II) chloride or bromide in DMF/DMSO at 130-140 °C leading to the corresponding aryl halides in moderate to good yields.     

An expeditious hydroxyamidation of carboxylic acids

Capitalizing on in situ activation with the cyclic phosphonic anhydride PPAA (1), the conversion of carboxylic acids into hydroxamic acids has been reduced to an experimentally simple one-pot operation that addresses the issue of polyacylation without resorting to a large excess of hydroxylamine or to protection. Scope and selectivity were satisfactory with a wide range of substrates, including α,β-unsaturated acids and hydroxyacids.     

Microbial deracemization of alpha-substituted carboxylic acids

An enzyme system of Nocardia diaphanozonaria JCM 3208 catalyzes the inversion of the chirality of various alpha-substituted carboxylic acids, such as 2-phenylpropanoic acid and 2-phenoxypropanoic acid derivatives, via a novel deracemization reaction.     

Oxidative coupling of carboxylic acid dianions

The conditions, scope, and stereochemical consequences of a versatile approach to succinic acid derivatives are described.     

Immobilization of carboxylic proteinases on amino-Silochrome

Summary Highly purified porcine pepsin and aspergillopepsin A immobilized on amino-Silochrome have been obtained. The enzymatic properties of these insoluble derivatives have been studied.All-Union Scientific-Research Institute of the Genetics and Breeding of Industrial Microorganisms, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 373–379, May–June, 1978.     

Capillary chromatography of polyfluorinated carboxylic esters

Retention indices and dI/dT values were obtained for members of six homologous and six pseudohomologous series of polyfluorinated saturated carboxylic esters on capillary columns with OV-101 or XE-60 as stationary phase. There was a nonlinear dependence of retention indices of fluorinated fatty acid esters on carbon chain length of homologs with m, n=1–6. A universal correlation equation was shown to describe the chromatographic behavior of polyfluorinated carboxylic esters.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1740–1745, August, 1991.     

Substituted hydrazides of hydroxy carboxylic acids

Under the action of concentrated sulfuric acid, a series of -alkyl--arylhydrazides of diarylglycolic acids is converted into 1-alkyl-1,2,3,4-tetrahydrocinnolin-3-ones. The reaction takes place through the intermediate formation of a halochromic salt.For Communication LXV, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 6, pp. 844–846, June, 1970.     

Photo-oxidation of unsaturated ferrocenyl-substituted carboxylic acids

In aqueous solution (pH 9) containing N₂O, the unsaturated acids $\text{trans}$-FcCHCH(CH₂)nCO₂H (n = 0 and 1) and FcCCCO₂H each undergo photo-oxidation, upon illumination with u.v. light of wavelength 240-250 nm, giving dipolar ferricenium species which may be chemically reduced back to the original acids. The mechanism of photo-oxidation, which is inhibited by ethanol, appears to be similar to that previously proposed for saturated ω-ferrocenylalkanoic acids.