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.

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.

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.

Some 2-substitution derivatives of 5-(4-oxo-6-hydroxy-3,4-dihydro-5-pyrimidinyl)pentanoic acid

1983 ◽  
Vol 48 (1) ◽  
pp. 304-311 ◽  
Author(s):  
Jiří Křepelka ◽  
Jan Beneš ◽  
Vladimír Pouzar ◽  
Jaroslav Vachek ◽  
Jiří Holubek
Keyword(s):  
Nitrile Group ◽  
Antineoplastic Activity ◽  
Carboxyl Group ◽  
Positional Isomers ◽  
Pentanoic Acid ◽  
Pharmacological Tests ◽  
Derivatives Of

Condensation of triethyl ester of 1,1,5-pentanetricarboxylic acid (XI) with substituted guanidines XXII - XXIX gave acids II - IX, which were converted into esters XI - XIX. The acid II and the ester XI were obtained as mixtures of positional isomers. Analogously, condensation of the triester XXI with dicyanodiamide gave rise to acid X, whose nitrile group, under conditions of esterification of a carboxyl group, produced iminoether XX. In pharmacological tests for antineoplastic activity the compounds prepared exhibited weaker efficacy than 5-(2-amino-6-hydroxy-4-oxo-3,4-dihydro-5-pyrimidinyl)pentanoic acid (I), employed as standard.

Synthesis of new maleimide derivatives of daunorubicin and biological activity of acid labile transferrin conjugates

1997 ◽  
Vol 7 (5) ◽  
pp. 617-622 ◽  
Author(s):  
Felix Kratz ◽  
Ulrich Beyer ◽  
Peter Schumacher ◽  
Michael Krüger ◽  
Heike Zahn ◽  
...  
Keyword(s):  
Biological Activity ◽  
Derivatives Of ◽  
Acid Labile

Bis(ether) derivatives of tetrakis(2-hydroxyphenyl)ethene — Direct synthesis of (E)- and (Z)-bis(2-hydroxyphenyl)-bis(2-methoxyphenyl)ethene via the McMurry olefination reaction

2006 ◽  
Vol 84 (10) ◽  
pp. 1250-1253 ◽  
Author(s):  
Mee-Kyung Chung ◽  
Paul Fancy ◽  
Jeffrey M Stryker
Keyword(s):  
Supramolecular Chemistry ◽  
Direct Synthesis ◽  
Protecting Groups ◽  
Tert Butyl ◽  
Orthogonal Protection ◽  
Protection Strategies ◽  
Titanium Trichloride ◽  
Sterically Hindered ◽  
Derivatives Of

The direct synthesis of sterically hindered, partially etherified derivatives of tetrakis(2-hydroxyphenyl)ethene is reported by using the McMurry reductive olefination reaction on a range of differentially substituted 2,2′-dialkoxy benzophenone substrates. Three orthogonal protection strategies are demonstrated, incorporating β-silylethyl, 3-butenyl, and tert-butyl protecting groups, respectively, into the starting benzophenones. The latter proved most efficient, with both the McMurry coupling and deprotection steps occurring concomitantly under the McMurry conditions to directly yield the desired bis(2-hydroxyphenyl)-bis(2-methoxyphenyl)ethene as a 1:1 mixture of E- and Z-diastereoisomers.Key words: preorganized polyaryloxide ligands, McMurry olefination, titanium trichloride, supramolecular chemistry, tetrakis(2-hydroxyphenyl)ethene, 2,2′-disubstituted benzophenone.

scholarly journals The Reaction of Derivatives of D-Xylal and D-Arabinal with Hydrogen Chloride and Hydrogen Bromide.

1969 ◽  
Vol 23 ◽  
pp. 2083-2094 ◽  
Author(s):  
Klaus Bock ◽  
Inge Lundt ◽  
Christian Pedersen ◽  
Tord Holme ◽  
Alf A. Lindberg ◽  
...  
Keyword(s):  
Hydrogen Chloride ◽  
Hydrogen Bromide ◽  
Derivatives Of

Di-t-Butyl Phosphorobromidate. A New Selective Phosphorylating Agent Containing Acid-Labile Protecting Groups

Synthesis ◽  
1977 ◽  
Vol 1977 (09) ◽  
pp. 623-625 ◽  
Author(s):  
Tadeusz GAJDA ◽  
Andrzej ZWIERZAK
Keyword(s):  
Protecting Groups ◽  
Acid Labile

scholarly journals Pyrimidine N-oxides. IV. The N,N'-dihydroxy derivatives of phenobarbital and veronal

1982 ◽  
Vol 35 (4) ◽  
pp. 795 ◽  
Author(s):  
W Cowden ◽  
NW Jacobsen
Keyword(s):  
Protecting Groups ◽  
Derivatives Of

5-Ethyl-1,3-dihydroxy-5-phenylbarbituric acid (N,N'-dihydroxyphenobarbital) and 5,5-diethyl-1,3-dihydroxybarbituric acid (N,N'-dihydroxyveronal) have been prepared by the condensation of 1,3-dibenzyloxyurea with ethylphenylmalonyl dichloride and diethylmalonyl dichloride respectively, followed by the removal of the benzyl protecting groups from the intermediate dibenzyloxy derivatives.

4,5-Seco-4,6-cyclosteroids. III. Observations on the course of reductive rearrangement of 6β-Bromo-4β,5-epoxy-5β-cholestan-3β-ol

1969 ◽  
Vol 22 (4) ◽  
pp. 807 ◽  
Author(s):  
DJ Collins ◽  
JJ Hobbs ◽  
RJ Rawson
Keyword(s):  
Hydrogen Bromide ◽  
High Yield ◽  
Lithium Aluminium Hydride ◽  
Experimental Conditions ◽  
Lithium Aluminium ◽  
Reaction Proceeds ◽  
Derivatives Of

It has been shown that reductive rearrangement of 6β-bromo-4β,5-epoxy- 5β-cholestan-3β-ol (I) to 4,5-seco-4,6-cycle-6β-cholestane-3β,5α-diol (IXa) with lithium aluminium hydride in tetrahydrofuran proceeds via 6β-bromo-5β-cholestane-3β,5-diol (IIa). Relevant reactions of the latter and the corresponding 3-ketone are discussed. ��� Similar conversion of the 3-epimer of (I) into 4,5-seco-4,6-cyclo- 6β-cholestane-3α,5α-diol (XIIIa) in high yield indicates that reductive rearrangement of the 6β-bromo-5β-hydroxy moiety proceeds without participation of the 3-aluminate complex. Some derivatives of (XIIIa) are described. ��� Experimental conditions required for the conversion of (I) into (IXa) are defined. ��� Combined evidence indicates that the reaction proceeds in a concerted manner by essentially base-catalysed, 1,3-elimination of hydrogen bromide from diol (IIa) with 4,5-bond migration to give the formal intermediate 3β-hydroxy-4,5-seco-4,6-cyclo-6β-cholestan-5-one (VI), further reduced to (IXa).

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