N-Nitroso-L-4-hydroxyproline as a precursor of intermediates for peptide synthesis

1971 ◽  
Vol 24 (6) ◽  
pp. 1277 ◽  
Author(s):  
FHC Stewart
Keyword(s):  
Peptide Synthesis ◽  
Protecting Groups ◽  
Practical Application ◽  
Acid Labile ◽  
Coupling Components

The N-nitroso derivative of L-4-hydroxyproline has been converted into various esters and other intermediates intended for use as coupling components in peptide synthesis. The preparative approach involved selective acidic cleavage of nitroso in the presence of different carboxyl-protecting groups, including the acid-labile 2,4,6- trimethylbenzyl moiety. Practical application of the new intermediates was illustrated by representative syntheses of crystalline protected L- 4-hydroxyproline peptides.

Use of N-2-cyanoethylglycine derivatives in the synthesis of peptides of N-2-carboxamidoethylglycine, an isomer of glutamine

1971 ◽  
Vol 24 (6) ◽  
pp. 1267 ◽  
Author(s):  
FHC Stewart
Keyword(s):  
Hydrogen Bromide ◽  
Nitrile Group ◽  
Protecting Groups ◽  
Derivatives Of ◽  
Acid Labile ◽  
Protected Peptides ◽  
Coupling Components

Derivatives of N-2-cyanoethylglycine have been employed as coupling components in the synthesis of protected peptides. The nitrile group in N-2-cyano-ethylglycine is readily hydrated by hydrogen bromide treatment with formation of N-2-carboxamidoethylglycine, which is an isomer of glutamine. This reaction, conducted on cyanoethyl intermediates with simultaneous cleavage of appropriate acid-labile protecting groups, was utilized to prepare several free peptides containing N-2-carboxamidoethylglycine residues.

scholarly journals Applications of Propargyl Esters of Amino Acids in Solution-Phase Peptide Synthesis

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
Ramesh Ramapanicker ◽  
Rohit Gupta ◽  
Rajendran Megha ◽  
Srinivasan Chandrasekaran
Keyword(s):  
Amino Acids ◽  
Peptide Synthesis ◽  
Free Amino ◽  
Solution Phase ◽  
The Other ◽  
Protecting Groups ◽  
Carboxyl Group ◽  
Neutral Reagent ◽  
Acid Labile ◽  
Propargyl Ester

Propargyl esters are employed as effective protecting groups for the carboxyl group during solution-phase peptide synthesis. The propargyl ester groups can be introduced onto free amino acids by treating them with propargyl alcohol saturated with HCl. The reaction between propargyl groups and tetrathiomolybdate is exploited to deblock the propargyl esters. The removal of the propargyl group with the neutral reagent tetrathiomolybdate ensures that most of the other protecting groups used in peptide synthesis are untouched. Both acid labile and base labile protecting groups can be removed in the presence of a propargyl ester. Amino acids protected as propargyl esters are employed to synthesize di- to tetrapeptides in solution-phase demonstrating the possible synthetic utilities of the methodology. The methodology described here could be a valuable addition to currently available strategies for peptide synthesis.

Phenyl-EDOTn derivatives as super acid labile carboxylic acid protecting groups for peptide synthesis

2008 ◽  
Vol 49 (20) ◽  
pp. 3304-3307 ◽  
Author(s):  
Albert Isidro-Llobet ◽  
Mercedes Álvarez ◽  
Fernando Albericio
Keyword(s):  
Carboxylic Acid ◽  
Peptide Synthesis ◽  
Protecting Groups ◽  
Super Acid ◽  
Acid Labile

Hafnium(IV) Chloride Catalyzes Highly Efficient Acetalization of Carbonyl Compounds

2019 ◽  
Vol 16 (6) ◽  
pp. 913-920 ◽  
Author(s):  
Israel Bonilla-Landa ◽  
Emizael López-Hernández ◽  
Felipe Barrera-Méndez ◽  
Nadia C. Salas ◽  
José L. Olivares-Romero
Keyword(s):  
Microwave Heating ◽  
Reaction Times ◽  
Protecting Groups ◽  
Catalyst Loading ◽  
Selective Protection ◽  
Highly Efficient ◽  
Aldehydes And Ketones ◽  
High Yields ◽  
Novel Catalyst ◽  
Acid Labile

Background: Hafnium(IV) tetrachloride efficiently catalyzes the protection of a variety of aldehydes and ketones, including benzophenone, acetophenone, and cyclohexanone, to the corresponding dimethyl acetals and 1,3-dioxolanes, under microwave heating. Substrates possessing acid-labile protecting groups (TBDPS and Boc) chemoselectively generated the corresponding acetal/ketal in excellent yields. Aim and Objective: In this study. the selective protection of aldehydes and ketones using a Hafnium(IV) chloride, which is a novel catalyst, under microwave heating was observed. Hence, it is imperative to find suitable conditions to promote the protection reaction in high yields and short reaction times. This study was undertaken not only to find a novel catalyst but also to perform the reaction with substrates bearing acid-labile protecting groups, and study the more challenging ketones as benzophenone. Materials and Methods: Using a microwave synthesis reactor Monowave 400 of Anton Paar, the protection reaction was performed on a raging temperature of 100°C ±1, a pressure of 2.9 bar, and an electric power of 50 W. More than 40 substrates have been screened and protected, not only the aldehydes were protected in high yields but also the more challenging ketones such as benzophenone were protected. All the products were purified by simple flash column chromatography, using silica gel and hexanes/ethyl acetate (90:10) as eluents. Finally, the protected substrates were characterized by NMR 1H, 13C and APCI-HRMS-QTOF. Results: Preliminary screening allowed us to find that 5 mol % of the catalyst is enough to furnish the protected aldehyde or ketone in up to 99% yield. Also it was found that substrates with a variety of substitutions on the aromatic ring (aldehyde or ketone), that include electron-withdrawing and electrondonating group, can be protected using this methodology in high yields. The more challenging cyclic ketones were also protected in up to 86% yield. It was found that trimethyl orthoformate is a very good additive to obtain the protected acetophenone. Finally, the protection of aldehydes with sensitive functional groups was performed. Indeed, it was found that substrates bearing acid labile groups such as Boc and TBDPS, chemoselectively generated the corresponding acetal/ketal compound while keeping the protective groups intact in up to 73% yield. Conclusion: Hafnium(IV) chloride as a catalyst provides a simple, highly efficient, and general chemoselective methodology for the protection of a variety of structurally diverse aldehydes and ketones. The major advantages offered by this method are: high yields, low catalyst loading, air-stability, and non-toxicity.

Selective acid hydrolysis of 2,4,6-trimethylbenzyl esters and its application in peptide synthesis

1966 ◽  
Vol 19 (8) ◽  
pp. 1511 ◽  
Author(s):  
FHC Stewart
Keyword(s):  
Acid Hydrolysis ◽  
Peptide Synthesis ◽  
Trifluoroacetic Acid ◽  
Ester Group ◽  
Protecting Groups ◽  
Alkaline Conditions ◽  
Hydrolysis Of

Experiments with various N-acylamino acid 2,4,6-trimethylbenzyl esters have shown that the ester group is cleaved selectively by cold trifluoroacetic acid without affecting benzyloxycarbonyl, formyl, or phthaloyl amino-protecting groups present. The possible value of this selective behaviour in peptide syntheses where the use of alkaline conditions would be detrimental is illustrated by the synthesis of certain dipeptide derivatives.

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