Preparation of hydrazides of amino acids and peptides

A new method of synthesizing hydrazides of amino acids and peptides is considered which involves the hydrazinolysis of the silyl esters of the corresponding compounds. A number of hydrazides of derivatives of amino acids and peptides has been obtained in high purity with yields close to quantitative. The physicochemical characteristics of the compounds synthesized are given.All-Union Scientific-Research Institute of the Technology of Blood Substitutes and Hormones Preparations, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 684–686, September–October, 1979.     

Preparation of hydrazides of amino acids and peptides

A new method of synthesizing hydrazides of amino acids and peptides is considered which involves the hydrazinolysis of the silyl esters of the corresponding compounds. A number of hydrazides of derivatives of amino acids and peptides has been obtained in high purity with yields close to quantitative. The physicochemical characteristics of the compounds synthesized are given.     

Site-specific modification of amino acids and peptides by aldehyde-alkyne-amine coupling under ambient aqueous conditions

A highly efficient method for the direct, site-specific functionalization of amino acids and peptides, under ambient conditions, is described. In aqueous, nearly solvent-free conditions, copper(I) chloride catalyzed the aldehyde-alkyne-amine (A(3)) coupling of amino acids to form dipropargylated products in moderate to excellent yields. The propargylamine functionality provides a convenient handle for further structural modifications, demonstrated by a subsequent one-pot deprotection and "click" reaction and a solution-phase peptide coupling.     

Cyclization under mild conditions of cysteine containing peptides

Cyclization of di- and tripeptides containing cysteine as N-terminal residue is reported. The preferred cyclization patterns and the nature of the products (diketopiperazine, aza-cyclol, peptide thiolactone) are discussed.     

Studies on amino acids and peptides—I : Synthesis of N-benzyloxycarbonylendo-thiodipeptide esters

N-Benzyloxycarbonylendothiodipeptide esters, 3, are synthesized without racemization from the corresponding N-benzyloxycarbonyldipeptide esters, 2, using 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane 2,4-disulfide, 1, as thionation reagent. The benzyloxycarbonyl amino-protecting group (Z) is removed from 3 by using HBr-AcOH.     

Morpholinization of aminoacyloxy acids and hydroxyacylamino acids and their esters under mass spectrometry conditions

Summary 1. Free hydroxyacylamino acids and their methyl esters, and also free aminoacyloxy acids, morpholinize under mass spectrometry conditions.2. In the mass spectrometry of methyl esters of aminoacyloxy acids and tert-butyl esters of aminoacyloxy acids and hydroxyacylamino acids no morpholinization takes place. These compounds behave similarly to the esters of acylated peptides and depsipetides.Khimiya Prirodnykh Soedinenii, Vol. 3, No. 5, pp. 325–327, 1967     

Preparation of trimethylsilyl derivatives of amino acids and peptides for peptide synthesis

Russian Chemical Bulletin -     

Nucleophilicities of amino acids and peptides

The kinetics of the reactions of amino acids with stabilized diarylcarbenium ions (Ar(2)CH(+)) have been studied photometrically in aqueous solution at variable pH. In the range of 10.5 < pH < 12, the amino acids react much faster than the competing nucleophiles hydroxide and water. Though the pK(aH) values of the amino acids vary by almost four units, the nucleophilic reactivities of all primary amino groups differ by less than a factor of 4. The secondary amino group of proline is 10(2) times more reactive, and the thiolate site in cysteine exceeds the reactivities of the primary amino groups by a factor of 10(4). Nucleophilicity parameters N as defined by the correlation log k(20 degrees C) = s(N + E) have been determined in order to include amino acids into the most comprehensive nucleophilicity scales presently available, which provide a direct comparison of n-, pi-, and sigma-nucleophiles.     

Preparation of differentially substituted 3,6-diaminopyridazines under mild conditions

Although desirable from a medicinal chemistry perspective, the differentially substituted 3,6-diaminopyridazine moiety is a highly challenging target using current literature approaches. Recent methods of Ullmann-type couplings are evaluated and a mild route to prepare these structures from iodide precursors is presented.     

Infrared spectra of amino acids and peptides

Summary The ionization constants of glycine, glycylglycine, DL--alanine, and -alanine have been determined from their IR spectra.Khimiya Priodnykh Soedinenii, Vol. 3, No. 2, pp. 197–201, 1967     

Organophosphorus analogs of amino acids and peptides

A method for obtaining phosphorus analogs of homoproline was developed, and the complexing properties of these compounds were studied. An effective method for obtaining optically active 1-aminoalkylphosphonic acids that is based on the stereoselective enzymatic hydrolysis of their N-acyl derivatives is proposed. New approaches to the synthesis of phosphonopeptides using privalyl chloride as the condensing agent, silylated amino phosphonic acids as the amino components of peptide synthesis, and the proteinase papain as the stereoselective catalyst for the formation of the peptide bond were developed.Institute of Bioorganic Chemistry and Petrochemistry, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 3, pp. 288–293, May–June, 1991. Original article submitted February 8, 1991.     

Enantioselective synthesis and enantiomeric amplification of amino acids under prebiotic conditions

A plausible origin of biomolecular homochirality is advanced, where alpha-methyl amino acids found on meteorites transfer their chirality in the synthesis of normal amino acids. This asymmetry can be amplified to nearly homochiral levels, thus providing the necessary prerequisite for life to start on this planet and elsewhere in the universe.