Pyrolysis of Amino Acid Derived Stabilised Ylides as a Route to Chiral Acetylenic Amines and Amino Acids and Gaba Analogues

Abstract

We recently reported the pyrolysis of stabilised ylides as a method for overall conversion of carboxylic acids to homologous acetylenic esters and terminal alkynes.^1,2 This has now been applied successfully to amino acids. A wide range of alkoxycarbonyl protected amino acids have been converted to the stable crystalline ylides 1. These have been fully characterised, and upon FVP, eliminate Ph₃PO to afford the protected acetylenic amino acids 2 in good yield and without significant racemisation. Subsequent reactions of these extremely versatile intermediates have been used to gain access to a wide variety of chiral amine and amino acids of great interest as potential selective enzyme inhibitors and components for modified peptide structures.     

Improved Yields in the Synthesis of Spin‐Labeled Fatty Acids

Abstract

Paramagnetic amide side products (6a–g) have been isolated from the reaction mixture in the synthesis of spin‐labeled fatty acids of the doxyl type. After their hydrolysis to the corresponding acid, 7, the overall yield of spin‐labeled fatty acids is significantly increased compared with published procedures.     

Synthesis of Novel Galactopyranosyl‐Derived Spiro Barbiturates

Abstract

Malonic acid undergoes condensation readily with ureas to yield barbituric acids 2, which on bromination give 5,5‐dibromobarbituric acids 3. Reaction of α‐D‐galactose with these 5,5‐dibromo barbituric acids afforded 2,3‐α‐D‐galactopyrano‐1,4‐dioxo‐7,9‐diaza‐spiro[4,5]deca‐6,8,10‐triones 4. The structures of the products have been assigned on the basis of ¹H NMR, ¹³C NMR, FAB‐MS, optical activity, and elemental analysis. The title compounds are found to have antibacterial and antifungal activities.     

The Quantitative Determination of some Phenolic Acids In Delphinium Formosum by HPLC

ABSTRACT

Some phenolic acids from the flowers of Delphinium formosum have been determined quantitatively by reversed-phase high-performance liquid chromatography with diode-array detection. A comparative study was performed by extracting the following phenolic acids: p-hydroxy benzoic, p-coumaric, caffeic, protocatechuic and vanillic acids with four different methods. The results were supported with recovery studies.     

Directed molecular recognition: furfurylamine appended ditopic receptor for succinic acid

A furfurylamine appended ditopic receptor (R1) for dicarboxylic acids has been designed and synthesised. The association constants (K_a) between receptors and dicarboxylic acids have been determined using UV–vis and NMR titration techniques. The binding constant (K_a) of succinic acid with R1 was observed maximum, which implies the optimum chain length selectivity for succinic acid. Theoretical calculation and molecular modelling using Gaussian 03 program also support the optimised receptor's cavity for succinic acid.     

Synthesis of Azetidin-2-Ones from Imines and Acids Using Trichloroacetonitrile-Triphenylphosphine Reagent

A one step synthesis of azetidin-2-ones (3a-j) has been described by the reaction of imines (1) with acids (2) in presence of trichloroacetonitrile, triphenylphosphine and triethylamine.     

Thin-Layer Chromatography of Bile Alcohols,Bile Acids and Conjugated Bile Acids

Abstract

Thin-layer chromatography of bile alcohols, bile acids and bile acid conjugates has been reviewed. Particular emphasis has been placed on the separation of the glycine and taurine conjugated bile acids as a class and as individual compounds, and on the isolation of bile alcohols and C₂₇ bile acids diastereo-isomeric at C-25.     

A ChemiluminesClent Precolumn Labelling Reagent for High-Performance Liquid Chromatography of Amino Acids

Abstract

A chemiluminescent tag for precolumn derivatization of amino acids has been developed. The tag, 4-isocyanatophthalhydrazide, couples with 17 amino acids tested, including proline and hydroxyproline, in less than ten minutes. Twelve derivatized amino acids have been separated and detected with an average detection limit of 10 femptomoles per 20 μL injection.     

HPLC-Analysis of PTH-Amino Acids

Abstract

Some of the problems that affect the usefulness of HPLC-analysis of PTH-amino acids have been examined. Four different C₁₈-reversed phase packings have been tested, together with different mobile phases. The separation problems of the Met/Val-group, the Phe/Leu/Ile/Lys-group and of the basic amino acids His and Arg on the reversed phase packings have been examined and solutions to some of the problems have been demonstrated. The sensitivity of the quantitative analysis of amino acids from a hydrolysate was determined.     

A 2-D dysprosium glutarate exhibiting slow magnetic relaxation and luminescent properties

Abstract

A 2-D dysprosium glutarate [Dy₂(glu)₃(phen)₂]_n (1, glu?=?glutarate, phen =1,10-phenanthroline) has been synthesized from the hydrothermal reaction of DyCl₃, glutaric acid, and phen ligand. Compound 1 displays a classical 2-D (4,4) grid structure constructed by the linkages of Dy³⁺ ions and three types of glutarate ligands. Compound 1 shows slow magnetic relaxation and luminescent properties. Although some lanthanide glutarates have been reported, they do not exhibit slow magnetic relaxation properties. Compound 1 offers the only example of a dysprosium coordination polymer with field-induced single-molecule magnets (SMMs) based on aliphatic dicarboxylic acids in the absence of ancillary aromatic carboxylic acids.     

Thia- and Sulfonyl-Calix[4]Arene Methylphosphonous Acids: Synthesis,Structure, and Amino Acids Binding

Abstract

Thia- and sulfonyl-calix[4]arene methylphosphonous acids have been synthesized by hydrolysis of corresponding alkyl esters. Host-Guest complexation of the thiacalix[4]arene tetrakis-methylphosphonous acid with a series of 12 amino acids has been investigated by HPLC and molecular modeling methods. Stability constants of the complexes are within 530—10,140 M^?1 in water contained solution.     

BIOLOGICALLY ACTIVE THIONES DERIVED FROM PYRIDAZINONES

Abstract

A number of pyridazin-3-thione (II), some hydrazinopyridazine derivatives (III) and its Schiff base (IV) have been prepared. α-(3-thiopyridazinyl)-β-aroylpropionic acids (VI) have also been synthesised. Structural evidences are discussed. The antibacterial activity of these compounds has been studied.     

MIXED ANHYDRIDES OF DIALKYLPHOSPHINOUS ACIDS AND DIALKYL HYDROGEN PHOSPHITES,AND THE ISOMERIC MONOXIDES

Abstract

The three isomers possible for oxidized 1,1-dialkyl-2,2-dialkoxydiphosphines, R₂(O)P–P(OR')₂ 1, R₂P–O–P(OR')₂ 2, and R₂P–P(O)(OR')₂ 3, have been synthesized. Irreversible transformations of 1 to 2 and 2 to 3 have been found and the rearrangement patterns, the role of electrophilic and nucleophilic catalysts are discussed. The fact that 3 is more stable than 1 is attributed to higher donor activity of the ligands attached to the four-coordinate phosphorus in 3. Acid chlorides have been shown to attack the phosphorus atom of ambident anions of trivalent phosphorus acids (the products are 1 and 3) whereas the acids proper react with the acid halides at the oxygen atom, to give 2.     

Zur Synthese von fungizid wirksamen Isocamphanderivaten: Synthesen in der Isocamphanreihe, 34. Mitt.

Summary Some esters of isocamphenilanic acid (4) have been prepared and tested for their fungicidal and insecticidal activity. Esters of various acids with isocamphanyl ethylalcohol (5) have also been synthesized and included in the fungicidal/acaricidal/insecticidal screening programme. All esters bear a geminal dimethyl group at C-3 of the bicyclus which is important because of its shielding effect.

     

Thin Later Chbomatography of Amino Acids on Tin(IV) Arsenosilicate Cation Exchanger in Some Buffer Solutions

Abstract

Inorganic ion exchanger tin(IV) arsenosillcate (TAS) has been used in the thin layer chromatographic study of 24 amino acids in various buffer solutions as the mobile phases. On the basis of the differential movement, some important binary separations of amino acids have been achieved, particularly those of basic fro acidic or neutral amino acids.     

New Derivatives of 1,2-Alkadienephosphonic Acids

Abstract

The preparations of new cyclic derivatives of 1,2-alkadienephosphonic acids have been reported and the reactions of these compounds with bromine have been investigated.     

Synthesis of Ureido-Linked Glycosylated Amino Acids from N α-Fmoc-Asp/Glu-5-oxazolidinones and Their Application to Neoglycopeptide Synthesis

A simple route for the synthesis of ureido-linked glycosylated amino acids has been described. The key step involves the reaction of isocyanates derived from N ^α-Fmoc-Asp/Glu-5-oxazolidinones 1 with glycosyl amines followed by hydrolysis. The resulting ureido-linked glycosylated amino acids have been incorporated into peptides. The overall procedure is simple, high-yielding, and involves fewer steps.     

Synthesis of Monocyclic β‐Lactams via Cyclodehydration of β‐Amino Acids Using POCl3

Abstract

β‐Lactams 2 have been synthesized through a convenient use of POCl₃ via cyclodehydration of β‐amino acids 1.     

DIMETHYL METHYLPHOSPHONATE AS METHYLATING REAGENT

Abstract

The methylating properties of dimethyl methylphosphonate have been investigated. Aromatic mono- and polycarboxylic acids were converted into their methyl esters by heating with dimethyl methylphosphonate. Similarly phenols or amines gave their respective O- or N-methyl derivatives. The sodium salts of sulfinic acids also reacted yielding sulfones in high yield.