- Solid-phase synthesis of a β-dodecapeptide with seven functionalized side chains and CD-spectroscopic evidence for a dramatic structural switch when going from water to methanol solution
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An all-β3-dodecapeptide with a protected N-terminal thiol-anchoring group and with seven side chains has been synthesized in multi-mg amounts by the manual solid-phase technique, applying Fmoc methodology and the Wang resin. The sequence is β-H
- Schreiber, Juerg V.,Seebach, Dieter
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- Homologation of α-amino acids to β-amino acids: 9-Fluorenylmethyl chloroformate as a carboxyl group activating agent for the synthesis of Nα-protected aminoacyldiazomethanes
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An efficient and stereospecific homologation of urethane-protected α-amino acids to β-amino acids by Arndt-Eistert approach using an equimolar mixture of Fmoc-/Boc-/Z-α-amino acid and 9-fluorenylmethyl chloroformate for the acylation of diazomethane synth
- Kantharaju,Suresh Babu, Vommina V.
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p. 2152 - 2158
(2007/10/03)
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- Conformationally homogeneous cyclic tetrapeptides: Useful new three-dimensional scaffolds
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The most commonly recognized motifs in protein-protein interactions are γ and β turns, which are defined by three to four contiguous amino acids in a peptide sequence. Cyclic tetrapeptides thus represent minimalist turn mimetics, but their usefulness is c
- Glenn, Matthew P.,Kelso, Michael J.,Tyndall, Joel D. A.,Fairlie, David P.
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p. 640 - 641
(2007/10/03)
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- Syntheses and CD-spectroscopic investigations of longer-chain β-peptides: Preparation by solid-phase couplings of single amino acids, dipeptides, and tripeptides
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The synthesis and CD-spectroscopic analysis of eleven water-soluble β-peptides composed of all-β3 or alternating β2- and β3-amino acids is described. Different approaches for the efficient syntheses of longer-chain β-pepti
- Arvidsson, Per I.,Frackenpohl, Jens,Seebach, Dieter
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p. 1522 - 1553
(2007/10/03)
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- Synthesis of β-amino acids: 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyl-uronium tetrafluoroborate (TBTU) for activation of Fmoc-/Boc-/Z-α-amino acids
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A new and efficient method for the homologation of urethane protected α-amino acids to its β-homomers by the Arndt-Eistert method using TBTU as a coupling agent is described. Several Fmoc-/Boc-/Z-protected α-amino diazoketone derivatives have been obtaine
- Patil, Basanagoud S.,Vasanthakumar, Ganga-Ramu,Suresh Babu
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p. 3089 - 3096
(2007/10/03)
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- Synthesis of Fmoc-/Boc-/Z-β-amino acids via Arndt-Eistert homologation of Fmoc-/Boc-/Z-α-amino acids employing BOP and PyBOP
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A simple and efficient protocol for Arndt-Eistert chain homologation of Fmoc-/Boc-/Z-α-amino acids using BOP or PyBOP as a coupling agent to the corresponding β-amino acids, synthesizing the key intermediate α-diazoketones as crystalline solids in good yield is described.
- Vasanthakumar,Babu, V. V. Suresh
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p. 1691 - 1695
(2007/10/03)
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- A convenient method for the synthesis of β-amino acids via the Arndt-Eistert approach using p-toluenesulphonyl chloride as a carboxylic group activating agent
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A simple method for the synthesis of Z-/Boc-/Fmoc-protected β-amino acids by the Arndt-Eistert approach employing p-toluenesulphonyl chloride for the activation of the carboxyl group of Nα-protected amino acid is described. The method is rapid and gave good yields with opitical purity.
- Vasanthakumar, Ganga-Ramu,Suresh Babu, Vommina V.
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p. 651 - 657
(2007/10/03)
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- Peptide folding induces high and selective affinity of a linear and small β-peptide to the human somatostatin receptor 4
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β-Peptides with side chains in the 2- and 3-positions on neighboring residues (of (S) configuration) are known to fold and form a turn (similar to an α-peptidic β-turn). Thus, we have synthesized an appropriately substituted β-tetrapeptide derivative to mimic the hormone somatostatin in its binding to the human receptors hsst1-5, which is known to rest upon a turn containing the amino acid residues Thr, Lys, Trp, and Phe. The N-acetyl-peptide amide Acβ3-HThr-β2-HLys-β3 -HTrp-β3-HPhe-NH2 (1) indeed shows all characteristics of the targeted turnmimic: Lys CH2 groups are in the shielding cone of the Trp indole ring (by NMR analysis, Figure 2) and there is high and specific nanomolar affinity for hsst4 receptor (Table 1). In contrast, the isomer 2 bearing the Lys side chain in 3-, rather than in the 2-position, has a 1000-fold smaller affinity to hsst4. The syntheses of the required Fmoc-protected β-amino acids (8-11, 17) are described (Schemes 1-3). Coupling of the β-amino acids was achieved by the manual solid-phase technique, on Rink resin.
- Gademann,Kimmerlin,Hoyer,Seebach
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p. 2460 - 2468
(2007/10/03)
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- β3-Amino acids by nucleophilic ring-opening of N-nosyl aziridines
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N-Nosyl aziridines can be easily prepared from 1,2-amino alcohols derived from α-amino acids. Nucleophilic ring-opening of N-nosyl aziridines with cyanide ions followed by hydrolysis of the corresponding nitriles lead to N-nosyl β3-amino acids, which can be readily converted into a variety of derivatives bearing adequate functionality for peptide synthesis. The proposed methodology is simple, efficient, and amenable to large-scale preparations.
- Farràs, Jaume,Ginesta, Xavier,Sutton, Peter W,Taltavull, Joan,Egeler, Frank,Romea, Pedro,Urpí, Fèlix,Vilarrasa, Jaume
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p. 7665 - 7674
(2007/10/03)
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- Convenient and simple synthesis of N-{[(9H-fluoren-9- yl)methoxy]carbonyl}-(Fmoc) protected β-amino acids (=homo-α-amino acids) employing Fmoc-α-amino acids and dicyclohexylcarbodiimide(DCC) mixtures
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A simple approach for the homologation of α-amino acids to β-amino acids by the Arndt-Eistert method employing Fmoc-α-amino acid and N, N1- dicyclohexylcarbodiimide (DCC) mixture for the acylation of diazomethane, synthesizing the key intermediates Fmoc-α-amino acyldiazomethanes as crystalline solids is described.
- Ananda,Suresh Babu
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p. 418 - 423
(2007/10/03)
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- Preparation of N-Fmoc-Protected β2- and β3-Amino Acids and Their Use as Building Blocks for the Solid-Phase Synthesis of β-Peptides
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N-Fmoc-Protected (Fmoc = (9H-fluoren-9-ylmethoxy)carbonyl) β-amino acids are required for an efficient synthesis of β-oligopeptides on solid support. Enantiomerically pure Fmoc-β3-amino acids (β3: side chain and NH2 at C(3)(=C(β))) were prepared from Fmoc-protected (S)- and (R)-α-amino acids with aliphatic, aromatic, and functionalized side chains, using the standard or an optimized Arndt-Eistert reaction sequence. Fmoc-β2-Amino acids (β2 side chain at C(2), NH2 at C(3)(=C(β))) configuration bearing the side chain of Ala, Val, Leu, and Phe were synthesized via the Evans' chiral auxiliary methodology. The target β3-heptapeptides 5-8, a β3- pentadecapeptide 9 and a β2-heptapeptide 10 were synthesized on a manual solid-phase synthesis apparatus using conventional solid-phase peptide synthesis procedures (Scheme 3). In the case of β3-peptides, two methods were used to anchor the first β-amino acid: esterification of the ortho-chlorotrityl chloride resin with the first Fmoc-β-amino acid 2 (Method I, Scheme 2) or acylation of the 4-(benzyloxy)benzyl alcohol resin (Wang resin) with the ketene intermediates from the Wolff rearrangement of amino-acid-derived diazo ketone 1 (Method II, Scheme 2). The former technique provided better results, as exemplified by the synthesis of the heptapeptides 5 and 6 (Table 2). The intermediate from the Wolff rearrangement of diazo ketones 1 was also used for sequential peptide-bond formation on solid support (synthesis of the tetrapeptides 11 and 12). The CD spectra of the β2- and β3-peptides 5, 9. and 10 show the typical pattern previously assigned to an (M) 31 helical secondary structure (Fig.). The most intense CD absorption was observed with the pentadecapeptide 9 (strong broad negative Cotton effect at ca. 213 nm); compared to the analogous heptapeptide 5, this corresponds to a 2.5 fold increase in the molar ellipticity per residue!
- Guichard, Gilles,Abele, Stefan,Seebach, Dieter
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p. 187 - 206
(2007/10/03)
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- Synthesis of Fmoc-β-homoamino acids by ultrasound-promoted wolff rearrangement
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A highly efficient protocol for Amdt-Eistert chain elongation of the base-labile fluorenylmethoxycarbonyl (Fmoc) protected α-amino acids by Ag+- catalyzed, ultrasound-promoted Wolff rearrangement of the corresponding α- diazo ketones at room temperature is described. The enantiomeric purity of the products was examined by capillary zone electrophoresis with chiral buffer systems.
- Müller, Annett,Vogt, Carla,Sewald, Norbert
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p. 837 - 841
(2007/10/03)
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- Convenient and stereospecific homologation of N-fluorenyl-methoxycarbonyl-α-amino acids to their β-homologues
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A very simple approach to the enantioselective homologation of α-amino acids is presented which is based on the formation of N-Fmoc-aminoacyldiazomethanes with nearly quantitative yields and on the complete retention of both chiral configuration and N-ter
- Leggio, Antonella,Liguori, Angelo,Procopio, Antonio,Sindona, Giovanni
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p. 1969 - 1971
(2007/10/03)
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