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An efficient and straightforward approach for the coupling of Nα-protected hydroxamic acids with an amino component in the presence of iodine is delineated. The reaction is mediated by the formation of unstable but reactive acyl nitroso intermediates. The peptide hydroxamic acids were found to be useful substrates in coupling reactions. [ABSTRACT FROM AUTHOR]

An efficient procedure for the synthesis of 3,5-disubstituted isoxazoles via reaction of in situ generated nitrile oxides with acetylenes employing readily preparable copper(0) nanoparticles is described. A variety of in situ generated nitrile oxide and acetylenic substrates were engaged in the study and found to undergo in short duration affording respective isoxazoles in excellent yield. Several amino acid-derived isoxazoles were also prepared in high yield. Consistent activity of the recovered catalyst was found to be almost same up to three cycles. [ABSTRACT FROM AUTHOR]

Thioacids derived from N-protected amino or dipeptide and tripeptide acids undergo facile N-acylation with aromatic amines to afford N-protected amino or peptide aryl amides in good to excellent yields and enantiopurities. The method also furnishes difficult-to-prepare N-Fmoc amino acid 4-nitroanilides in good yields. This simple oxidative Nα-acylation of thioacids with aromatic amines proceeds in the presence of iodine, 1-hydroxybenzotriazole and N,N-diisopropylethylamine at room temperature in tetrahydrofuran. [ABSTRACT FROM AUTHOR]

Propanephosphonic acid anhydride (T3P®) is a prevailing coupling and dehydrating agent with many desirable properties which render it a reagent of choice for a plethora of reactions and, befittingly, its application in organic synthesis is rapidly increasing. Since its introduction as a peptide coupling agent in 1980, the realm of applications of T3P has expanded. Currently its use is found in a broad range of reactions, including condensation, functional group transformation, heterocycles preparation, rearrangements, and catalysis. It offers several advantages over traditional reagents, such as high yield, chemical and optical purity, broad functional group tolerance and easy work-up. The reagent is attractive for large-scale synthesis as well, and particularly so for multi-kilogram scale preparations of drug molecules. This article reviews the hitherto reported applications of T3P as a reagent in organic synthesis. Focus is also placed on the use of T3P for large-scale synthesis. [ABSTRACT FROM AUTHOR]

A simple and efficient method is described for the synthesis of thio-, dithio- and selenothiocarbamate-linked peptidomimetics. The nucleophilic addition of enantiopure Nα-protected amino alkyl thiols to isocyanates, isothiocyanates or isoselenocyanates obtained from amino acid esters proceeds smoothly in the presence of catalytic amount of DMAP. The protocol was further extended for the synthesis of N,N'-orthogonally protected thio-, dithio- and selenothiocarbamate-linked peptidomimetics. The reaction is mild, free from racemization, and the products were obtained in good yield. [ABSTRACT FROM AUTHOR]

We report herein an efficient protocol for the synthesis of N-urethane-protected α-amino/peptide thioacids from their corresponding acids mediated by EDC and Na2S. The fast reaction under mild conditions enabled the process to be completed in shorter duration with good yield circumventing column purification. The chemistry is compatible with a wide variety of urethane protecting groups, side-chain functionalities, and sterically hindered amino acids. [ABSTRACT FROM AUTHOR]

Non-Schotten-Baumann conditions are described for the hydantoin-free synthesis of peptide ester isocyanates using activated zinc dust as a non-basic HCl scavenger. Also, the procedure gives no N-acylated products in the case of the conversion of amino acid and peptide amides into isocyanates. [ABSTRACT FROM AUTHOR]

A simple and efficient protocol for the synthesis of Nβ-Fmoc/Z-amino alkyl thiols is described. The approach uses sodium pyrosulfite-mediated hydrolysis of isothiouronium salts resulting from the reaction between N-protected aminoalkyl iodides and thiourea. N-Protected taurines were prepared through performic acid oxidation of the thiols and the products were further utilized for the synthesis of dipeptidosulfonamides. [ABSTRACT FROM AUTHOR]

Synthetically useful Nβ-Fmoc amino alkyl isonitriles are prepared conveniently from Nβ-Fmoc amino alkyl thioformamides via a cyanogen bromide mediated dehydrosulfurization. The reaction is fast, clean, and yields are good. [ABSTRACT FROM AUTHOR]

A facile one-pot procedure for the synthesis of urea-linked peptidomimetics and neoglycopeptides under Curtius rearrangement conditions employing Deoxo-Fluor and TMSN3 is described. The method is efficient and circumvents the isolation of acyl azide and isocyanate intermediates. The rearrangement of the in situ generated acyl azide via the acyl fluoride was carried out under ultrasonication followed by amine capture to insert a urea bond. The protocol worked well with all the common N-urethane-protected amino acids and also with a sugar-6-acid. [ABSTRACT FROM AUTHOR]

The article presents three chemical equations for the synthesis of Nα protected amino and peptide acid aryl amides via iodine-mediated oxidative acylation of Nα protected amino and peptide thioacids, published in a 2013 issue of the journal "Synthesis."

The known Ugi 5-centre 3-component reaction (U-5C-3CR) is restricted to the synthesis of peptidomimetic methyl esters such as (V), caused by the lesser reactivity of other alcohols compared to methanol (IV) during solvolysis of the cyclic intermediate. [ABSTRACT FROM AUTHOR]

One-pot click chemistry of N(α)-Boc-bromomethylketones, NaN3 and propiolic acid affords N-Boc protected 1,4-disubstituted 1,2,3-β-ketotriazole acids in good to excellent yield. The use of CuI as catalyst and DMSO as solvent leads the click reaction to efficient, practical and column-free preparation of the title compounds. The utility of the resulting unnatural amino acids as building blocks to prepare triazole possessing peptidomimetics is also delineated.

Synthesis of Nα-protected amino acyl azides starting from corresponding acids via the carbonyldiimidazole (CDI) activation is described. The protocol is extended for a one-pot preparation of ureido peptides that circumvents the isolation of acyl azide and isocyanate intermediates. The reaction was accomplished without using any additives and base. The protocol is simple, clean, high yielding and free from racemization.

We report a one pot synthesis of Fmoc amino acid derived 4-amino-thiazole derivatives and thiazole linked N-orthogonally protected dipeptidomimetics by the condensation of N(alpha)-Fmoc alpha-halomethylketones with thiourea and Boc/Z-alpha-amino acid thioamides via modified Hantzch protocol. Side chain modified Fmoc amino acids containing 4-amino thiazole moiety have also been synthesized following the similar protocol.