Convenient amidation of carboxyl group of carboxyphenylboronic acids

The use of catalysts in the activation of carboxyl groups towards nucleophilic attack and the protection of other functional groups by suitable protecting groups are standard and necessary procedures in amide bond formation. In contrast to the usual methods, various new compounds, amides of APTES ((3-aminopropyl)triethoxysilane, 3-triethoxysilylpropylamine) and carboxyphenylboronic acids, as well as the amides of aniline and carboxyphenylboronic acids, were obtained in good yields by a one-step synthesis under mild conditions without using any coupling reagents or additional catalysts.     

Effects of functional group interactions in the chemical ionization mass spectra of some substituted cis-1,3-cyclopentane dicarboxylic acids and their derivatives

Ammonia, isobutane and methane chemical ionization mass spectra have been measured for some substituted cis-1,3-cyclopentane dicarboxylic acids and their derivatives. The relative proton affinities of the different functional groups determine the protonation site in the molecule and thereby greatly affect the fragmentation. Intramolecular catalysis clearly facilitates the elimination of water in cases where functional groups can interact with each other.     

Elimination of water from the carboxyl group of GlyGlyH+

The elimination of water from the carboxyl group of protonated diglycine has been investigated by density functional theory calculations. The resulting structure is identical to the b(2) ion formed in the mass spectrometric fragmentation of protonated peptides (therefore named "b2" in this study). The most stable geometry of the fragment ion ("b2") is an O-protonated diketopiperazine. However, its formation is kinetically disfavored as it requires a free energy of 58.2 kcal/mol. The experimentally observed N-protonated oxazolone is 3.0 kcal/mol less stable. The lowest energy pathway for the formation of the "b2" ion requires a free energy of 37.5 kcal/mol and involves the proton transfer from the amide oxygen of protonated diglycine to the hydroxyl oxygen. Fragmentation initiated by proton transfer from the terminal nitrogen has also a comparable free energy of activation (39.4 kcal/mol). Proton transfer initiating the fragmentation, from the highly basic terminal nitrogen or amide oxygen to the less basic hydroxyl oxygen is feasible at energies reached in usual mass spectrometric experiments. Amide N-protonated diglycine structures are precursors of mainly y(1) ions rather than "b2" ions. In the lowest energy fragmentation channels, proton transfer to the hydroxylic oxygen, bond breaking and formation of an oxazolone ring occur concertedly but asynchronously. Proton transfer to hydroxyl oxygen and cleavage of the corresponding C-O bond take place at the early stages of the fragmentation step, while ring closure to form an oxazolone geometry occurs at the later stages of the transition. The experimentally observed low kinetic energy release is expected to be due to the existence of a strongly hydrogen bonded protonated oxazolone-water complex in the exit channel. Whereas the threshold energy for "b2" ion formation (37.1 kcal/mol) is lower than for the y(1) ion (38.4 kcal/mol), the former requires a tight transition state with an activation entropy, DeltaS++ = -1.2 cal/mol.K and the latter has a loose transition state with DeltaS++ = +8.8 cal/mol.K. This leads to y(1) being the major fragment ion over a wide energy range.     

Chalcogen arsenide clusters of iron with a functional carboxyl group: Synthesis, structures, and thermolysis

The carbonyl clusters [Fe₃(??₃-Q)(??₃-AsR)(CO)₉] (Q = Se and Te; R = meta- and para-HOOCC₆H₄) were obtained from the salts K₂[Fe₃(??₃-Q)(CO)₉] and organoarsenic diiodides RAsI₂ prepared by reducing iodination of arsonic acids RAsO(OH)₂ according to a novel method. The structures of the clusters were identified by X-ray diffraction. The crystal packing motifs of the dimers of the cluster molecules and their relationship with the solubility of the clusters are discussed. The sequential steps of the thermolysis (decarbonylation, decarboxylation, and decomposition of the organic fragment) of the clusters were studied. The presence and location of the carboxyl group does not influence the decarbonylation temperature.     

Organic functional group analysis via gas chromatography. I. Microdetermination of carboxyl groups

Summary A gas-chromatographic procedure for the microdetermination of carboxyl groups by decarboxylation is described. The sample is heated in the presence of quinoline and cupric carbonate in a closed vessel; the carbon dioxide formed is then driven into the gas chromatograph. The peak-height on the chromatogram varies linearly with the amount of carboxylic acid in the sample. The method is rapid, simple, and accurate.

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Zusammenfassung Ein gaschromatographisches Verfahren für die Mikrobestimmung von Carboxylgruppen durch Decarboxylierung wurde beschrieben. Die Probe wird in Gegenwart von Chinolin und Kupfer(II)-carbonat in einem geschlossenen Gefäß erhitzt. Das freigesetzte Kohlendioxid wird in einen Gaschromatographen geleitet. Die Höhe der Zacken des Chromatogrammes entspricht der Menge an Carbonsäure in der Probe. Die Methode ist rasch, einfach und genau.

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Résumé On décrit un procédé chromatographique en phase gazeuse pour le microdosage des groupes carboxyliques par décarboxylation. On chauffe l'échantillon avec de la quinoléine et du carbonate de cuivre-II, dans un récipient fermé et l'on fait arriver le gaz carbonique qui se forme, dans l'appareil de chromatographie en phase gazeuse. La hauteur du pic sur le chromatogramme varie linéairement avec la quantité d'acide carboxylique de l'échantillon. La méthode est rapide, simple et précise.

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Dedicated to Prof. Dr.A. A. Benedetti-Pichler on the occasion of his 70th birthday.     

The synthesis of tetrafluoro-sulphobenzoic acids and their derivatives

The tetrafluorosulphobenzoic acids 1,2-HO₂C.C₆F₄.SO₃H (I) and 1,4-HO₂C.C₆F₄.SO₃H (II) have been synthesised [1] by oxidation of respectively 4,5,6,7-tetrafluorobenzo [b] thiophen- 2-carboxylic acid (III) [2] and 4-mercaptotetrafluorobenzoic acid (IV) [3].By-products were obtained when (III) was oxidised with either trifluoroperacetic acid or potassium permanganate.A number of reactions of these intermediates have been investigated and the products characterized, eg reaction of (I) with SoCl₂ gave tetrafluoro-1,2-sulphobenzoic acid cyclic anhyride (V). Although no significant change was observed when (II) was similarly treated reaction of (II) with DMF/SOCl₂ gave 1,4-Cl.C₆F₄.COCl. The diacid fluorides 1,2-FOC.C₆F₄.SO₂F (VI) and 1,4-FOC.C₆F₄.SO₂F (VII) were obtained when (I) and (II) respectively were reacted with sulphur tetrafluoride. The use of excess SF₄ gave 1,2- or 1,4- [F₃C.C₆F₄.SO₂F].     

Conformation of some carboxylic acids and their derivatives

The conformation in the crystalline state of some aliphatic carboxylic acids and their derivatives has been analysed. This analysis, based upon the results of structure determinations by means of X-ray diffraction, seems to support the concept that the conformation of a molecule is governed chiefly by intramolecular interactions.     

Organocatalytic asymmetric synthesis of alpha,alpha-disubstituted alpha-amino acids and derivatives

It is shown that racemic oxazolones are excellent reagents for the synthesis of chiral quaternary amino acids and its derivatives by the diastereo- and enantioselective nucleophilic addition to alpha,beta-unsaturated aldehydes catalyzed by diarylprolinol silyl ethers. The scope of this new organocatalytic reaction is demonstrated for different oxazolones having aromatic and alkyl groups at the reactive carbon atom and different aromatic and aliphatic substituted alpha,beta-unsaturated aldehydes, for which the stereoselective reaction proceeds with good yield, moderate to good to very high diastereoselectivity, and very high enantioselectivity. The potential of the reaction is shown for the synthesis of optically active alpha,alpha-disubstituted alpha-amino acids, alpha-quaternary proline derivatives, amino alcohols, lactams, and tetrahydropyranes. Furthermore, we have calculated by DFT-methods the transition-state structures that account for both the diastereo- and enantioselectivity observed for the addition of oxazolones to the alpha,beta-unsaturated aldehydes. For one class of compounds, the stereoselectivity is controlled by a hydrogen-bonding interaction of the enolate-form of the oxazolone with an ortho-hydroxy-phenyl substituent of the alpha,beta-unsaturated aldehyde, whereas the benzhydryl-protecting group in the oxazolone determines the diastereo- and enantioselectivity in a more general manner for both aromatic and aliphatic alpha,beta-unsaturated aldehydes.     

The reactions of aroylpyruvic acids and their derivatives witho-aminophenyldiphenylmethanol

Aroylpyruvic acids and their methyl esters react witho-aminophenyldiphenylmethanol to form 4-aryl-2-[2-(1-hydroxydiphenylmethyl)phenylamino]-4-oxobut-2-enoic acids and their esters. The α-enamino acids obtained undergo intramolecular heterocyclization in the presence of Ac₂O to affort substituted 4,5-dihydrobenzo[e][1,4]oxazepin-3(1H)-ones. The reaction of 5-arylfuran-2,3-diones witho-aminophenyldiphenylmethanol leads to products of decyclization, 2-(1-hydroxydiphenylmethyl)phenylamides of 4-aryl-2-hydroxy-4-oxobut-2-enoic acid, which upon heating in AcOH or Ac₂O yield 3-aroylacetyl-1,1-diphenyl-1H-benzo[d][1,3]oxazines. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2317–2319, November, 1998.     

Synthesis of new monoterpene sulfonic acids and their derivatives

The oxidation of monoterpene thiols with chlorine dioxide afforded new water-soluble sulfonic acids and their derivatives (sulfonothioates and sulfonyl chlorides). The reaction of terpene thiols with ClO₂ gave the corresponding trisulfides. Sulfonothioates with a pinane skeleton showed antibacterial and antifungal activity.     

Biological activity of selected boronic acids and their derivatives

A series of substituted phenylboronic acids and benzoxaboroles were evaluated for their antimicrobial activity. Antibacterial and antifungal action activity of several compounds was tested against Escherichia coli 67, Staphylococcus aureus 209‐p, Mycobacterium luteum VCM B‐868, Aspergillus niger VCM F‐1119 and Candida tenuis VCM Y‐70. Substituted phenylboronic acids have low biological activity against all the investigated species. Benzoxaboroles reveal higher biological activity in comparison with the corresponding acids. The highest activity was observed for small benzoxaborole molecules, and the unsubstituted benzoxaborole has only slightly lower biological activity as compared with the 5‐fluoro‐substituted one (AN2690). The compound possessing two oxaborole fragments has very high biological activity towards Mycobacterium luteum and both investigated fungi. Copyright © 2012 John Wiley & Sons, Ltd.     

Homochiral 4-hydroxy-5-hexenoic acids and their derivatives and homologues from carbohydrates

Efficient routes to chiral 4-hydroxy-5-hexenoic acids and lactones from d-gluconic acid-δ-lactone and l-mannonic acid-γ-lactone are described. In this approach, the starting lactones are converted to 2,6-dibromo compounds that readily undergo zinc mediated elimination to generate the terminal alkene group in concert with 2-deoxygenation. The integrity of the remaining stereocenters is preserved during the reaction. The related important pharmaceutical intermediates (S)-3-hydroxy-4-pentenoic acid and (S)-1,3-dihydroxy-4-pentene were also prepared from 2-deoxyribose via the corresponding aldonolactone.     

Syntheses of N-phenylaminomethylenediphosphonic and -diphosphinic acids and their derivatives

Russian Journal of General Chemistry -     

New method for the synthesis of thioglycidic acids and their derivatives

Conclusions A new method was described for the preparation of thioglycidic acids and their derivatives.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1788–1794, August, 1973.     

土槿皮酸类化合物的质谱研究

本文系统地研究了土槿皮甲酸、乙酸和丙酸及其衍生物的质谱.通过质谱-结构关系的分析、高分辨质谱及亚稳数据的测定,阐明了它们在电子轰击下的裂解反应机制.