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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 268-276 
    ISSN: 0899-0042
    Keywords: absolute configuration ; peptidomimetics ; retro-inverso modifications ; 2-aminocyclopentanecarboxylic acid ; nuclear magnetic resonance (NMR) ; nuclear Overhauser effect ; bioactive peptides ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A modern method is reported for the assignment of absolute configuration for peptidomimetics in bioactive peptides by use of 1H-NMR parameters in solution. Four peptide systems incorporating either retro-inverso modifications or 2-aminocyclopentanecarboxylic acid (2-Ac5c) as a peptidomimetic for proline are discussed. (1) Two 14-membered cyclic dermorphin analogs Tyr-c[D-A2bu-Phe-gPhe-(S and R)-mLeu] with a reverse amide bond between gPhe and mLeu residues where gPhe denotes a gem-diamino analog of Phe and mLeu refers to a malonyl analog of Leu. (2) Two cyclic hexapeptides related to somatostatin, c[gSar6-(S and R)-mPhe7-D-Trp8-Lys9-Thr10-Phe11], with a reverse amide bond between the gSar and mPhe residues where the gSar and mPhe denote the gem-diamino and malonyl analogs of the Sar and Phe residues, respectively. The superscript numbers refer to positions in native somatostatin. (3) Cyclic hexapeptide somatostatin analogs containing 2-Ac5c [trans-(1S,2S)-2-Ac5c, trans-(1R,2R)-2-Ac5c, cis-(1R,2S)-2-Ac5c, and cis-(1S,2R)-2-Ac5c] in place of proline c[(2-Ac5c)6-Phe7-D-Trp8-Lys9-Thr10-Phe11]. (4) Morphiceptin related analogs incorporating a cis-2-Ac5c residue as shown in Tyr-cis-2-Ac5c-Phe-Val-NH2. The methodology described in this investigation could be applied to a wide variety of peptide systems.
    Additional Material: 7 Ill.
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  • 2
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isoproterenol analogues 4a and 4b, synthesized as mixtures of Diastereoisomers, were shown to possess very potent β-adrenoceptor agonistic activity. Therefore, the four possible diastereoisomers of 4a have been synthesized and tested for inotropic activity. The (6R, 2′R)-diastereoisomer turned out to be the most interesting one. Consequently, also (6R,2′R)-4b has been prepared and tested. For the diastereoselective synthesis, three variants have been elaborated: (i) coupling of epoxides 12 with amines 27 (Scheme 6); (ii) coupling of the activated glycol 17 with the amine 22 (Scheme 8); (iii) diastereoselective hydrogenation of the amino ketone 31 (Scheme 7). Both (6R,2′R)-4a and (6R,2′R)-4b show long lasting positive inotropic activity after intravenous as well as oral administration and are at least three times as potent as rac-isoproterenol. In the anesthetized dog, a good separation of positive inotropic and positive chronotropic effects is observed. In conscious dogs, however, heart rate and contractile force increase to the same extent (possibly due to reflex tachycardia).
    Additional Material: 2 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 10 (1998), S. 28-34 
    ISSN: 0899-0042
    Keywords: collagen ; nuclear magnetic resonance (NMR) ; nuclear Overhauser effect (NOE) ; stereospecific assignment ; triple-helix ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An improved model-based method for the stereospecific assignment of prochiral centers in collagen-like triple-helical molecules is introduced. Using the concepts of reporter atoms and of ensemble NOEs, the proposed methodology extracts the stereochemical information contained in the chiral elements of triple-helices and transfers it to prochiral centers with nondegenerate proton resonances. The improved approach has been successfully validated using -(Gly-Pro-Hyp)n- triple-helices for which the stereospecific assignment was previously obtained with established techniques. We have applied our stereochemical characterization to novel peptoid containing triple-helices for which existing methods of stereospecific assignment can not be used for all the prochiral centers. In our approach, several different NOE measurements are employed to make a given stereospecific assignment. The multiple NOE comparisons allow internal cross checks, which reduce the chance of erroneous assignments caused by experimental artifacts including spin diffusion and bias from anisotropic rotational motions. In addition, the multiple NOE comparisons are useful in overcoming problems associated with resonance overlap often encountered in the 1H-NMR spectra of collagen-like molecules. Our stereochemical analysis is anticipated to improve the precision and accuracy of the characterization of collagen-like triple-helices through a better correlation of structures with their 1H-NMR spectra. Chirality 10:28-34, 1998. © 1998 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 705-714 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational behavior of POE-bound model peptides Boc-(L-Ala)2-X-Y-(L-Ala)2-NHPOE (X - Y = L-Pro-Gly (I), Gly-L-Ile (II); NHPOE = aminopoly(oxyethylene)) as well as of the repetitive hexapeptide of elastin, Boc-L-Val-L-Ala-L-Pro-Gly-L-Val-Gly-A-NHPOE-M (III) (A = photosensitive 3-nitro-4-(bromomethyl)benzoyl group; NHPOE-M = aminopoly(oxyethylane) monomethyl ether) has been studied by means of 1H-NMR and CD spectroscopy. Compounds I and III form a β-turn with Pro and Gly in positions i + 1 and i + 2, respectively, while an aggregated state for II, has been identified. The results are in good agreement with published prediction codes giving experimental evidence for the dominance of short-range interactions to establish secondary structure in solution.
    Additional Material: 4 Ill.
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