Enantiomerically Enriched Bicyclic Hydroxamic Acids in One Step from α-Aminohydroxamic Acids and Keto Acids via Cyclocondensation

New enantiomerically enriched bicyclic hydroxamic acids, 1-hydroxy-dihydro-1H-pyrrolo[1,2-a]imidazole-2,5(3H,6H)-diones, have been synthesized by the cyclocondensation of L-α-aminohydroxamic acids with keto acids in a highly chemo- and stereoselective manner. The cis configuration between the amino acid side chain and the methyl group at C7a in 1H-pyrrolo[1,2-a]imidazole-2,5-dione was unambiguously established by X-ray crystallographic analysis. This method could also be applied to the cyclocondensation with o-formylbenzoic acid, giving a tricyclic hydroxamic acid in a good yield.

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The Synthesis of Cyclic Amino Acids

Several cyclic amino acids (1-4) were synthesized from glycine. Isocyanate ester was prepared as the key intermediate and reacted with dibromoalkanes to afford the target compounds.     

Synthesis of Boc-Amino Tetrazoles Derived from α-Amino Acids

A simple route for the synthesis of Boc-protected tetrazole analogs of amino acids starting from N ^α-Boc amino acids has been described. The [2 + 3] cycloaddition of Boc-α-amino nitrile and sodium azide in the presence of a catalytic amount of zinc bromide yielded the desired tetrazoles in good yields and purity. All the compounds obtained have been characterized by ¹H and ¹³C-NMR and mass spectral studies.     

Synthesis of a new Class of Chiral β—Mercaptoalcohols from Amino Acids

The syntheses of three new optically active β-mercaptoalcohols,(R)-1,1-diphenyl-2-mercapto-3-methyl-1-butanol,(R)-1,1-diphenyl-2-mercapto-4-methyl-1-pentanol,and (R)-1,1-diphenyl-2-mercapto-1-benzenepropanol from the corresponding amino acids are described.The enantiomeric excesses of these β-mercaptoalcohols were determined by ^1H NMR as their (S)-mandeloyl derivatives.     

Diastereoselective α—Alkylation of β—Amino Esters：Preparation of Novel α—Substituted β—Amino Esers from α—Amino Acids

Enantiomerically pure α-substituted β-amino esters were prepared from natural L-α-amino acids through Arndt-Eistert homologation and diastereoselective α-alkylation.     

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.     

Reactions of (Arene) Tricarbonylchromium Complexes with Anions from Schiff Bases of α-Amino Esters: Synthesis of α-Aryl Amino Acids

We report here a convenient synthesis of α-substituted aryl amino acids: Schiff bases 1 derived from α-amino esters were arylated with halogeno aryl chromium tricarbonyl complex to produce, after oxydation or hydrolysis, α-aryl amino esters 4.     

Synthesis of Novel Dendrimers Containing Amino Acids and Peptides

Dendrimers are known for their well-defined, regular, highly branched architectures with a large number of functional groups1. Recently, dendrimers have been widely researched in different fields, such as molecular light havesting, catalysts, liquid cryst…     

The Simple Synthesis of Chiral Polyazaoxacoronands Derived from α-Amino Acids

Abstract

Bisamidation of oxaloyl chloride using L-amino acid methyl ester hydrochlorides afforded chiral diesters. The following reactions of diesters with 2,2-(ethylene-dioxy)diethylamine, afforded tetramides possessing C₂ symmetry. Coupling of N-hydroxysuccinimide ester of N-benzyloxycarbonyl-L-alanine with 1,5-diamino-3-oxapentane, followed by cleavage of protecting groups, afforded an optically active diamine, which was transformed consequently into tetramide via the reaction with diglycolic acid dimethyl ester under high pressure conditions.     

Simple and Mild One-Pot Synthesis of Dipeptidyl Ureas via Carbamoyl Azides of α-N-Protected Amino Acids

A simple and mild one-pot synthesis of potentially bioactive α-N-protected dipeptidyl ureas is reported. The procedure involves the reaction between the carbamoyl azide of an α-N-protected amino acid and an α-amino acid methyl ester. The reaction is fast (3 h at 45 °C), regardless of the nature of both the reagents, and racemization free. The reported protocol represents a valid alternative to existing methods.

Enantioselective Synthesis of Amino Acids Based on Nucleophilic Reactions of Enolates

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Asymmetric Synthesis of Highly Enantiomerically Enriched (S)(-)-β-Bisabolene

(S)-β-Bisabolene, (S)-1, was synthetized by a synthetic route in which (S)-4-methyl-3-cyclohexene carboxylic acid, (S)-10, which was the key intermediate, was prepared via a highly diastereoselective TiCl₄-catalyzed Diels-Alder reaction between isoprene and the acrylate of commercial (R)-pantolactone, followed by hydrolysis. Compound (S)-10 was then converted into ketone (S)-13 using two different procedures. The best one of these, as regards the degree of stereospecificity, involved the reaction of (S)-10 with 2 equiv of 4-methyl-3-penten-1-yllithium, 14, in the presence of CeCl₃, and gave (S)-13 having ca. 84% ee. The Zr-promoted methylenation of this ketone afforded highly enantiomerically enriched (S)-1.     

Initiation of Protein Synthesis with Non-Canonical Amino Acids In Vivo

By transplanting identity elements into E. coli tRNA^fMet, we have engineered an orthogonal initiator tRNA (itRNA^Ty2) that is a substrate for Methanocaldococcus jannaschii TyrRS. We demonstrate that itRNA^Ty2 can initiate translation in vivo with aromatic non-canonical amino acids (ncAAs) bearing diverse sidechains. Although the initial system suffered from low yields, deleting redundant copies of tRNA^fMet from the genome afforded an E. coli strain in which the efficiency of non-canonical initiation equals elongation. With this improved system we produced a protein containing two distinct ncAAs at the first and second positions, an initial step towards producing completely unnatural polypeptides in vivo. This work provides a valuable tool to synthetic biology and demonstrates remarkable versatility of the E. coli translational machinery for initiation with ncAAs in vivo.     

A Facile Synthesis of N-Phosphoryl Amino Acids Containing Hydroxy Group

three kinds of N-(diisopropyloxyphosphoryl) amino acids containing hydroxyl group were prepared in high yield by using diisopropyl phosphite as the phosphorylating agent, sodium hypochlorite as the chlorinating agent and tetrabutyl ammonium bromide as the phase transfer catalyst in basic aqueous media.     

Polyenolates of Unsaturated Carboxylic Acids in Synthesis. Synthesis of Unsaturated α-Amino Acids and β-Hydrazing Acids

Regioselective reaction of lithium diene-and triene-diolates 1 and 2 with O-diphenylphosphinyl hydroxylamine affords unsaturated α-amino acids 3 and 4. Addition to DEAD leads selectively to γ-hydrazino unsaturated acids 5 and 6.     

Synthesis of α-N-Ethylamino Acids and their Derivatives

 A new synthesis of α-N-ethylamino acids starting from α-amino acids using hexafluoroacetone as protecting and activating agent is described. The hexafluoroacetone-protected N-ethylamino acid derivatives obtained are activated lactons. Therefore, they can be directly transformed without the need of an additional activation step with various nucleophiles into the corresponding carboxylic acid derivatives.     

Diastereoselective Synthesis of Enantiopure Cyclic α-Aminophosphonic Acids

A new and efficient route for the synthesis of cyclic aminophosphonic acids by the reaction of dialkylchlorophosphites with β-aldiminoalcohols has been described.     

Synthesis of Chiral Nitrones from N‐Fmoc Amino Acids and N‐Fmoc Dipeptides

Abstract

In this work is presented a synthetic procedure for the preparation of chiral nitrones from N‐Fmoc protected amino acids and dipeptides. The nitrone functional group can replace the carboxyl unit of amino acid and peptide systems and can be inserted into the peptide chain. The introduction of the 1,3‐dipole in peptide segments can improve the solubility and the stability toward enzymatic degradation.     

A Method for Preparing Phosphinic Acids from Hypophosphites: III. Synthesis of α-Hydroxy Phosphinic Acids

A one-pot method is proposed for preparing unsymmetrical -hydroxy phosphinic acids from ammonium hypophosphite. Bis(trimethylsilyl) phosphonites formed in situ on addition of bis(trimethylsilyl) hypophosphite to activated unsaturated compounds are brought without isolation into the Abramov reaction with an aldehyde or ketone. A series of new -hydroxy phosphinic acids are obtained.