scholarly journals Semisynthetic analogues of insulin. The use of N-substituted derivatives of methionine as acid-stable protecting groups

1977 ◽  
Vol 165 (3) ◽  
pp. 479-486 ◽  
Author(s):  
Derek J. Saunders ◽  
Robin Offord
Keyword(s):  
Protecting Groups ◽  
Amino Groups ◽  
Fat Cell ◽  
Selective Protection ◽  
Acid Cleavage ◽  
Active Ester ◽  
Cleavage Step ◽  
Cell Test ◽  
Derivatives Of ◽  
Acid Stable

1. We describe the use of benzyloxycarbonylmethionine and ethoxycarbonylmethionine for the selective protection of the amino groups of glycine-A1 and lysine-B29 of pig insulin. We have used the Edman method to remove residues from the N-terminal and of the B-chain of the NA1NB29-di-protected derivatives. The benzyloxycarbonyl group shows slight but noticeable lability in the acid-cleavage step, but the ethoxycarbonyl group remained intact even after five cycles of degradation. 2. We have prepared the following truncated forms of insulin via the di(ethoxycarbonylmethionyl) derivative: des-PheB1-insulin;des-(PheB1-ValB2)-insulin; des-(PheB1-ValB2-AsnB3)-insulin;des- (PheB1-ValB2-AsnB3-GlnB4)-insulin; des-(PheB1-ValB2-AsnB3 -GlnB4-HisB5)-insulin. 3. Insulin was re-synthesized from the di-protected des-PheB1-insulin by reaction with an active ester of t-butoxycarbonyl-l-phenylalanine. The product after deprotection crystallized, and the immunoreactivity of the crystalline material was identical with that of the native protein. 4. We have prepared the following analogues of insulin in a similar manner: [l-AlaB1]insulin; [l-ValB1]insulin; [l-TyrB1]insulin; [m-F-l-PheB1]insulin; [o-F-l-PheB1]-insulin; [o-F-l-PheB2]des-PheB1-insulin. All had between 34 and 62% of the activity of insulin in the fat-cell test. 5. We have also investigated the use of the benzyol, toluene-p-sulphonyl, p-nitrobenzyloxycarbonyl and 2,4-dinitrophenyl groups for the N-protection of the methionine active esters. Each should have had some particular advantage over the benzyloxycarbonyl and ethoxycarbonyl groups, but all proved in practice to have disadvantages that more than outweighed anything in their favour.

scholarly journals Useful access to enantiomerically pure protected inositols from carbohydrates: the aldohexos-5-uloses route

2016 ◽  
Vol 12 ◽  
pp. 2343-2350 ◽  
Author(s):  
Felicia D’Andrea ◽  
Giorgio Catelani ◽  
Lorenzo Guazzelli ◽  
Venerando Pistarà
Keyword(s):  
Aldol Condensation ◽  
Biomimetic Synthesis ◽  
Protecting Groups ◽  
Reaction Conditions ◽  
Enantiomerically Pure ◽  
Selective Protection ◽  
Inductive Effects ◽  
State Models ◽  
Derivatives Of ◽  
Mechanism Of The Reaction

The intramolecular aldol condensation of aldohexos-5-ulose derivatives of the D-xylo and L-ribo stereoseries has been studied. Only one of the four possible inososes was isolated from both stereoseries in reasonable yields (30–38%). The results obtained, together with the previous findings for the L-arabino and L-lyxo stereoseries, allowed for the rationalisation of a mechanism of the reaction based on open-transition-state models and electron-withdrawing inductive effects. Complementary reductions of the intermediate inososes were possible by changing the reaction conditions, and two isomeric inositol derivatives were obtained with complete stereoselection from each inosose. The presented approach permits us to control the configuration of three out of the six stereocentres of the inositol frame and gives access to seven of the nine inositols. Noteworthy, for the D-xylo derivative, the two-step sequence (condensation followed by reduction with NaBH(OAc)3) represents the biomimetic synthesis of myo-inositol. Furthermore, the sugar-based pathway leads directly to enantiomerically pure selectively protected inositols and does not require any desymmetrisation procedure which is needed when myo-inositol and other achiral precursors are employed as starting materials. As an example of application of the method, the indirect selective protection of secondary inositols’ hydroxy functions, by placing specific protecting groups on the aldohexos-5-ulose precursor has been presented.

A Simple Method of Preparation of Labelled Peptides Possessing Antibiotic Properties

1971 ◽  
Vol 26 (5) ◽  
pp. 451-453 ◽  
Author(s):  
Miloš Havránek ◽  
Karel Vereš
Keyword(s):  
Amino Acid ◽  
Free Amino ◽  
Polymyxin B ◽  
Substantial Part ◽  
Peptide Antibiotics ◽  
Amino Groups ◽  
Simple Method ◽  
Protected Amino Acid ◽  
Active Ester ◽  
Derivatives Of

Preparation of derivatives of peptide antibiotics polymyxin B and colistin- substituted on free amino groups by aminoacyl residues is described. The first procedure is based on the condensation of the antibiotic with active ester of a suitably protected amino acid. The second one makes use of Woodward’s reagent by condensation of the antibiotic with a protected amino acid. The following compounds were prepared: glycyl-14C-polymyxin B and glutaminyl-polymyxin B and glycylcolistin, also under conditions suitable for a radioactive synthesis. All the preparations preserve a substantial part of the biological activity comparable with polymyxin B and colistin.

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.

[1-β-Mercaptopropionic acid, 8-norarginine]vasopressin and [1-β-mercaptopropionic acid, 8-D-norarginine]vasopressin. Two analogs with strong biological effects

1979 ◽  
Vol 44 (4) ◽  
pp. 1179-1186 ◽  
Author(s):  
Milan Zaoral ◽  
František Brtník ◽  
Martin Flegel ◽  
Tomislav Barth ◽  
Alena Machová
Keyword(s):  
Biological Effects ◽  
Disulfide Bridge ◽  
Protecting Groups ◽  
Pressor Effect ◽  
Amino Groups ◽  
Mercaptopropionic Acid ◽  
Antidiuretic Effect ◽  
Carbodiimide Method

[1-β-Mercaptopropionic acid, 8-norarginine]vasopressin (L8, D8; I, II) was prepared by condensation of β-benzylthiopropionyl-tyrosyl-phenylalanyl-glutaminyl-asparaginyl-S-benzylcysteine with Nγ-benzyloxycarbonyl-α,γ-diaminobutyryl-glycine amide (L2, D2) by the azide or carbodiimide method, respectively, removal of the benzyloxycarbonyl residue, guanidination of γ-amino groups, removal of protecting groups, closing of the disulfide bridge, and electrophoretic purification. I has an almost 2 times higher antidiuretic effect than DDAVP and a 3 times higher pressor effect than AVP. II has 20-25% of the antidiuretic effect of DDAVP and 16 IU/mg of the pressor effect.

Coupling of Steroid O-(Carboxymethyl)oxime Derivatives with Single-Protected α,ω-Diaminoalkanes

1999 ◽  
Vol 64 (12) ◽  
pp. 2035-2043 ◽  
Author(s):  
Vladimír Pouzar ◽  
Ivan Černý ◽  
Pavel Drašar
Keyword(s):  
Trifluoroacetic Acid ◽  
Protecting Groups ◽  
Oxime Group ◽  
Amino Groups ◽  
New Approach ◽  
Terminal Amino ◽  
Oxime Derivatives

New approach to the synthesis of steroid oximes bearing O-substituents with terminal amino groups was described. The easily accessible steroid O-(carboxymethyl)oximes were reacted with single-protected Boc-α,ω-diaminoalkanes to give corresponding amide intermediates. From them the Boc protecting groups were cleaved with trifluoroacetic acid to afford the desired steroid derivatives with terminal amino groups. The procedure was succesfully tested on steroids with O-(carboxymethyl)oxime group in positions 7 and 17. The decomposition of target products was observed during deprotection of substituted 19-oximes.

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 Role of capping in peptide synthesis

2020 ◽  
Vol 11 (4) ◽  
pp. 5225-5228
Author(s):  
Deepshikha Verma ◽  
Pillai V N R ◽  
Giriraj Tailor
Keyword(s):  
Peptide Synthesis ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Protecting Groups ◽  
Amino Groups ◽  
Peptide Chemistry ◽  
Fmoc Spps ◽  
Reliable Methods ◽  
Important Test

Protecting groups like Fmoc and coupling both steps are essential to monitoring the Fmoc SPPS (Solid Phase Peptide Synthesis) reaction completion. Reliable methods are used to detect the unreacted number of amino groups for monitoring these two essential reaction steps of coupling and cleavage. The ability to detect the complete coupling, incomplete coupling or failure of coupling we use many colour tests in the laboratory and based on this the Fmoc peptide chemistry allows the control of the completion of the Fmoc cleavage. The most important test used is the Kaiser test and highly recommended to monitor the coupling and cleavage steps. If the result of colour tests is positive after coupling, then the second coupling should be performed. Then again use the colour test to detect the level of coupling. If the result is still slightly positive, repeat coupling with the smaller modification of reagents such as used PyBOP instead of HOBT AND HOAT. These colour tests help in revealing the presence of unreacted amino-functional groups. Thus, we need to block these free N-terminal of amino- acids which help in avoiding the making of deletion of sequence.

scholarly journals Appendix: Synthesis of N-acylglutathione derivatives by dimethylaminopyridine catalysis

1982 ◽  
Vol 207 (2) ◽  
pp. 329-332 ◽  
Author(s):  
Claudius D'Silva ◽  
Amina Al-Timari ◽  
Kenneth T. Douglas
Keyword(s):  
General Procedure ◽  
Amino Groups ◽  
Derivatives Of

A general procedure, involving 4-dimethylaminopyridine-catalysed acylation of the amino groups in the appropriate S-blocked glutathione, is reported for the preparation of N-blocked derivatives of glutathiones.

Protecting Groups

2008 ◽  
Author(s):  
Jie Jack Li ◽  
Chris Limberakis ◽  
Derek A. Pflum
Keyword(s):  
Low Temperature ◽  
Organic Synthesis ◽  
Secondary Alcohol ◽  
Primary Alcohol ◽  
Protecting Groups ◽  
Silyl Ether ◽  
Benzyl Ether ◽  
Protecting Group ◽  
Selective Protection ◽  
Death Taxes

In his book, Protecting Groups, Philip J. Kocieński stated that there are three things that cannot be avoided: death, taxes, and protecting groups. Indeed, protecting groups mask functionality that would otherwise be compromised or interfere with a given reaction, making them a necessity in organic synthesis. In this chapter, for each protecting group showcased, only the most widely used methods for protection and cleavage are shown. Also, this section is not comprehensive and only addresses some of the most common blocking groups in organic synthesis. For a thorough review of protecting groups, the reader should consult the following references: (a) Wuts, P. G. M.; Greene, T. W.; Protective Groups in Organic Synthesis, 4th ed.; Wiley: Hoboken, NJ, 2007; (b) Kocienski, P. J. Protecting Groups, 3rd edition.; Thieme: Stuggart, 2004. In this section, the formation and cleavage of eight protecting groups for alcohols and phenols are presented: acetate; acetonides for diols; benzyl ether; para-methoxybenzyl (PMB) ether; methyl ether; methoxymethylene (MOM) ether; tert-butyldiphenylsilyl (TBDPS) silyl ether; and tetrahydropyran (THP). Acetate is a convenient protecting group for alcohols—easy on and easy off. Selective protection of a primary alcohol in the presence of a secondary alcohol can be achieved at low temperature. The drawback of this protecting group is its incompatibility with hydrolysis and reductive conditions.

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