40829-66-1Relevant articles and documents
Efficient access to enantiopure γ4-amino acids with proteinogenic side-chains and structural investigation of γ4- asn and γ4-ser in hybrid peptide helices
Jadhav, Sandip V.,Misra, Rajkumar,Singh, Sumeet K.,Gopi, Hosahudya N.
, p. 16256 - 16262 (2013/12/04)
Hybrid peptides composed of α- and β-amino acids have recently emerged as new class of peptide foldamers. Comparatively, γ- and hybrid γ-peptides composed of γ4-amino acids are less studied than their β-counterparts. However, recent investigations reveal that γ4-amino acids have a higher propensity to fold into ordered helical structures. As amino acid side-chain functional groups play a crucial role in the biological context, the objective of this study was to investigate efficient synthesis of γ4-residues with functional proteinogenic side-chains and their structural analysis in hybrid-peptide sequences. Here, the efficient and enantiopure synthesis of various N- and C-terminal free-γ4-residues, starting from the benzyl esters (COOBzl) of N-Cbz-protected (E)-α,β-unsaturated γ-amino acids through multiple hydrogenolysis and double-bond reduction in a single-pot catalytic hydrogenation is reported. The crystal conformations of eight unprotected γ4-amino acids (γ4-Val, γ4-Leu, γ4-Ile, γ4-Thr(OtBu), γ4-Tyr, γ4-Asp(OtBu), γ4- Glu(OtBu), and γ-Aib) reveals that these amino acids adopted a helix favoring gauche conformations along the central Cγi￡ Cβ bond. To study the behavior of γ4- residues with functional side chains in peptide sequences, two short hybrid γ-peptides P1 (Ac-Aib-γ4-Asn-Aib-γ4-Leu- Aib-γ4-Leu-CONH2) and P2 (Ac-Aib- γ4-Ser-Aib-γ4-Val-Aib-γ4-Val- CONH2) were designed, synthesized on solid phase, and their 12-helical conformation in single crystals were studied. Remarkably, the γ4-Asn residue in P1 facilitates the tetrameric helical aggregations through interhelical H bonding between the side-chain amide groups. Furthermore, the hydroxyl side-chain of γ4-Ser in P2 is involved in the interhelical H bonding with the backbone amide group. In addition, the analysis of 87 γ4-residues in peptide single-crystals reveal that the γ4-residues in 12-helices are more ordered as compared with the 10/12- and 12/14-helices. Copyright
Studies toward diazonamide A: Initial synthetic forays directed toward the originally proposed structure
Nicolaou,Snyder, Scott A.,Huang, Xianhai,Simonsen, Klaus B.,Koumbis, Alexandros E.,Bigot, Antony
, p. 10162 - 10173 (2007/10/03)
A brief introduction into the chemistry of diazonamide A (1) is followed by first-generation sequences to access the originally proposed structure for this unusual marine natural product. These explorations identified a route capable of delivering a model compound possessing the complete heteroaromatic core of the natural product, highlighting in the process several unanticipated synthetic challenges which led both to new methodology as well as an improved synthetic plan that was successfully applied to fully functionalized intermediates.
Synthesis and biological activity of new potential agonists for the human adenosine A2A receptor
Bosch, M. Pilar,Campos, Francisco,Niubó, Itziar,Rosell, Gloria,Díaz, J. Luis,Brea,Loza, M. Isabel,Guerrero, Angel
, p. 4041 - 4053 (2007/10/03)
New adenosine derivatives have been synthesized and tested as putative agonists of adenosine receptors. Compounds 2-6 derive from the introduction of several types of substituents (electron donating, electron withdrawing, and halogens) in the para-position of the phenyl ring of the parent compound 1, and compound 7 lacks the hydroxyl group of amino alcohol 1. In radioligand binding assays using recombinant human A1, A2A, A2B, and A3 receptors, all compounds showed very low or negligible affinity for A1 and A2B receptors but compounds 3, 5, and 7 displayed a remarkably potent affinity for the A2A receptor with Ki values of 1-5 nM. Bromo derivative 3 displayed a selectivity A1/A2A = 62 and A3/A2A = 16 whereas the presence of a hydroxyl group (compound 5) improved the selectivity of A 1/A2A and A3/A2A to 120- and 28-fold, respectively. When the methoxy derivative 4 lacks the hydroxyl group on the side chain (compound 7), the binding affinity for A2A is increased to 1 nM, improving selectivity ratios to 356- and 100-fold against A1 and A3, respectively. In Chinese hamster ovary cells transfected with human A2A and A2B receptors, most compounds showed a remarkable activity for the A2A receptor, except chloro derivative 2, with EC50 values ranging from 1.4 to 8.8 nM. The compounds behaved as good A2A agonists, and all were more selective than 5′-(N-ethylcarboxamino)adenosine (NECA), with A2B/A 2A ratios of cAMP accumulation ranging from 48 for compound 2 to 666 for compound 7 while the corresponding A2B/A2A ratio for NECA was only 9. Compounds 1, 3, 5, and 7 also displayed higher selectivities than NECA up to 100-fold in isolated aortas of rat and guinea pig. In guinea pig tracheal rings precontracted by carbachol, compounds 2 and 4 were more potent than adenosine (100-fold) and NECA (10-fold), whereas compounds I and 7 displayed similar effects to NECA. Pretreatment of the tracheal rings with A2, A2A, and A2B receptor antagonists 3,7-dimethyl-L-propargylxanthine, 8-(3-chlorostyryl)caffeine, and alloxazine produced a marked inhibition of the tracheal relaxations induced by compounds 1, 2, and 4, but none of the compounds showed selectivity toward any of the adenosine receptors.
