- A low-epimerizing peptide coupling reagent based on the rearrangement of a carboxylic-sulfonic mixed anhydride
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A series of peptides has been prepared using an o-hydroxybenzenesulfonyl chloride as the condensation reagent. Experimentally, the coupling is a one pot two-steps reaction: formation and aminolysis of a substituted aryl ester. The first step occurs by an
- Cabaret, Daniel,Wakselman, Michel
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- 15N NMR Spectroscopy. 30 - Structure/Shift Relationships of Oligopeptides and Copolypeptides, Including Gramicidin S.
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The 15N NMR spectra of various oligopeptide derivatives of the Z-X-Y-Y-OMe structure, where X and Y are variable amino acids and Z is the benzyloxycarbonyl group, were measured in several protic and aprotic solvents.The shift difference of the 15N of the
- Kricheldorf, Hans R.
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- 5-Nitro-3H-1,2-benzoxathiole SS-Dioxide, a New Reagent for Coupling in Peptide Synthesis
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Peptides are rapidly prepared and isolated by a two-step, one-pot reaction using 5-nitro-3H-1,2-benzoxathiole SS-dioxide (1), a strained sultone, as a condensation agent.
- Wakselman, Michel,Acher, Francine
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- Zinc-catalyzed amide cleavage and esterification of β- hydroxyethylamides
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Snipping tool: Zn(OTf)2 is an efficient catalyst for selective cleavage of amides bearing a β-hydroxyethyl group on the nitrogen atom. The mechanism involves an N,O-acyl rearrangement and transesterification. This new catalytic system can be applied to sequence-specific peptide bond scission at the amine side of a serine residue. Tf=trifluoromethanesulfonyl. Copyright
- Kita, Yusuke,Nishii, Yuji,Higuchi, Takafumi,Mashima, Kazushi
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supporting information; body text
p. 5723 - 5726
(2012/08/07)
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- Facile amide formation via S -nitrosothioacids
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Here we report a novel amide bond formation strategy from simple thioacid and amine starting materials. The reaction is mediated by unstable but very reactive S-nitrosothioacid intermediates. This fast reaction under mild conditions should be useful in synthesis.(Figure Presented)
- Pan, Jia,Devarie-Baez, Nelmi O.,Xian, Ming
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supporting information; experimental part
p. 1092 - 1094
(2011/04/25)
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- Concise total syntheses of variecolortides A and B through an unusual hetero-Diels-Alder reaction
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A fusion of certain anthraquinones and diketopiperazines is an apt description of the variecolortides, a family of unusual fungal alkaloids. In a new, concise total synthesis of the variecolortides A and B, the natural racemates are obtained highly convergently and almost without protecting-group manipulations. The spirocyclic core is generated in a hetero-Diels-Alder reaction of a 1,4-anthraquinone with a didehydrodiketopiperazine.
- Kuttruff, Christian A.,Zipse, Hendrik,Trauner, Dirk
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supporting information; experimental part
p. 1402 - 1405
(2011/04/21)
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- Reactivity of dehydroamino acids and dehydrodipeptides towards N- bromosuccinimide: Synthesis of β-bromo- and β,β- dibromodehydroamino acid derivatives and of substituted 4-imidazolidinones
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We have developed a modification of our previously reported high-yielding method for the synthesis of N,N-diacyldehydroamino acid derivatives to prepare N-monoprotected dehydroamino acids and dehydrodipeptides. Thus, several dehydroalanine, dehydroaminobutyric acid and dehydrophenylalanine derivatives have been prepared by treating the corresponding L-serine, L-threonine and D,L-3-phenylserine (threo-type) derivatives with 1 equiv. of di-tert-butyl dicarbonate and 4-(dimethylamino)pyridine. The reaction proceeded with the initial formation of an O-tert-butyl carbonate which, by treament with N,N,N′,N′-tetramethylguanidine, underwent β elimination to give the corresponding dehydroamino acid derivative. This two-step method can be carried out as a one-pot procedure and is stereoselective, giving only the Z isomer. The N-monoprotected dehydroamino acids were treated with N-bromosuccinimide and thereafter with triethylamine to afford several β,β-dibromodehydroalanines or β-bromo-, β-alkyl- or β-aryldehydroalanines. The latter were obtained as mixtures of E and Z isomers. An increased stereoselectivity towards the formation of the Z isomer was observed with dehydrophenylalanine and when 4-tolylsulfonyl was used as the N-protecting group. In the case of dehydrodipeptides, the reaction with NBS and triethylamine afforded the corresponding brominated dehydrodipeptides when the N-protecting group was other than 4-tolylsulfonyl. However, when the reagent was a peptide with a dehydroamino acid as the second residue and an N-(4-tolylsulfonyl) group the corresponding 2,2-disubstituted 1-(4-tolylsulfonyl)imidazolidin-4-ones were obtained in good-to-high yields. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
- Ferreira, Paula M. T.,Monteiro, Luis S.,Pereira, Goreti,Ribeiro, Liliana,Sacramento, Joana,Silva, Liseta
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p. 5934 - 5949
(2008/09/17)
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- Protein backbone modification by novel C(α)-C side-chain scission
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α-Ketoamide (-NH-CO-CO-) units in intact peptides are generated from Ser/Thr residues via Ru(VIII)-catalyzed C(α)-C side-chain scission. Facets associated with this novel α-carbon modification have been probed with 75 peptides chosen to represent every possible peptide environment. The reactions were carried out at room temperature with in situ generated Ru(VIII) in biphasic (CH3CN/CCl4/pH 3 phosphate buffer, 1:1:2 v/v) medium. Whereas Ser/Thr residues placed at the C-terminal end in peptides undergo N-C bond scission leading to des-Ser/Thr peptide amides - thus acting as Gly equivalents in simulating the α-amidating action of pituitary enzymes - those located at the N-terminal or nonterminal or even at the C-terminal position (protected as amide) were found to undergo oxidative C-C bond scission (involving C(α) and C side-chain bond), resulting in the generation of α-ketoamide (-NH-CO-CO-) units in the intact peptide backbone. The difference in the products arising from C(α)-C side-chain scission of Ser/Thr esters and amides is rationalized on the basis of a common mechanism involving either oxaloesters [PeP-NH-CO-COX; X = OMe] or oxalamides [X = NH2 or NH-Pep] arising from the oxidation of initially formed carbinolamide intermediates [Pep-NH-CH(OH)-COX], wherein, while the former are shown to undergo hydrolysis to terminal amides [Pep-NH2], the oxalamides are found to be stable to hydrolysis. Ancillary noteworthy findings are those of peptide bond scission when contiguous Ser-Ser/Thr-Thr residues are present and the oxidative cleavage at C-terminal Tyr/Trp sites generating des amides. The oxidative methodology presented here is mild, simple, and practical and proceeds with chiral retention. The insensitivity of a large number of amino acid residues, such as Gly, Ala, Leu, Asn, Gln, Asp, Glu, Pro, Arg, Phe, Lys, Val, and Aib, and N-protecting groups, such as Boc, Z, and Bz, toward Ru(VIII) under the experimental conditions should make this methodology practical and useful. Sulfur-containing amino acids Cys and Met get oxidized to sulfones in the products.
- Ranganathan,Vaish,Shah
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p. 6545 - 6557
(2007/10/02)
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- Peptide Synthesis with Benzo- and Naphthosultones
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6-Nitro- and 6,8-dinitronaphth-1,2-oxathiole S,S-dioxides (7b and 7c) have been prepared from the parent naphthosultone 7a and compared with 5-nitrobenz-3H-1,2-oxathiole S,S-dioxide (1b) as coupling reagents for peptide synthesis.Nucleophilic attack of a carboxylate salt on these strained five-membered sultones leads to activated esters 3 and 9 which rapidly react with amines (except in the case of 9c).The rate constant for the formation of ester 9b is higher than that of 3b.Amides or peptides are formed in slightly better yields with the naphthosultone 7b than with the benzosultone 1b.The naphthosultones are also preferred over the benzosultones from the point of view of amount of 5(4H)-oxazolone formation from N-benzoyl amino acids and the degree of racemization.However the rate of alkaline hydrolysis of 7b is slower than that of 1b.All these results may be rationalized by a better intramolecular acyl transfer reaction in the more rigid mixed anhydride intermediate 8b.There is no dependence on in the rate equation for aminolysis of esters 3b and 9b by benzylamine in THF, acetonitrile, or DMF and the aminolysis is probably anchimerically assisted by a neighbouring S=O group.Esters 3b are more selective acylating agents for primary amino groups in the presence of secondary ones than esters 9b and this observation is exploited in a synthesis of maytenine by selective acylation of spermidine.
- Acher, Francine,Wakselman, Michel
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p. 4133 - 4138
(2007/10/02)
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