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  • Wiley-Blackwell  (11)
  • 1985-1989  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Geometry and Conformation of the α-Aminoisobutyric Acid Residue in Simple Derivatives and Dipeptides. Four New X-ray Structural Analyses and a Statistical Analysis from Known Crystal Data (1987)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1987 (1987), S. 1055-1060 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Geometrie und Konformation des α-Aminoisobutyryl-Restes in einfachen Derivaten und Dipeptiden. Vier neue Röntgen-Struktur-Analysen und eine statistische Analyse mit bekannten KristalldatenDie Resultate der Röntgen-Strukturanalysen von zwei α-Aminoisobuttersäure(Aib)-Derivaten, N-Acetyl-α-aminoisobuttersäure-methylester (Ac-Aib-OMe, 1) und N-(Benzyloxycarbonyl)-α-aminoisobuttersäure-benzylester (Z-Aib-OBzl, 2) sowie von zwei terminal blockierten Aib enthaltenden Dipeptiden, N-Acetyl-L-alanyl-α-aminoisobuttersäure-methylester (Ac-L-Ala-Aib-OMe, 3) und N-(Benzyloxycarbonyl)-α-aminoisobutyryl-L-alanin-tert-butylester (Z-Aib-L-Ala-OtBu 4), werden beschrieben. In der asymmetrischen Zelle aller vier Verbindungen befinden sich zwei unabhängige Moleküle. In allen Fällen außer einem (Molekül A von 3) ist der Aib-Rest gefaltet, die Torsionswinkel Θ, ψ (oder Θ, ψτ) fallen in den Bereich der Konformationsenergiekarte, wo α- und 310-Helices liegen. Eine vergleichende statistische Analyse der Bindungslängen, Bindungswinkel und Torsionswinkel aus Kristallstrukturen von 20 Aib-Derivaten und 11 Aib enthaltenden linearen Dipeptiden wurde durchgeführt. Diese liefert genaue Information über die Geometrie und Konformation des Aib-Restes ohne den Einfluß der Restriktionen durch intramolekulare Wasserstoffbrücken, denen längere gefaltete oder helikale Peptide ausgesetzt sind.
    Notes: The results of X-ray diffraction analyses on two α-aminoisobutyric acid (Aib) derivatives, methyl α-(acetylamino)isobutanoate (Ac-Aib-OMe, 1) and benzyl α-[(benzyloxycarbonyl)amino]isobutanoate (Z-Aib-OBzl, 2), and two terminally blocked, Aib-containing dipeptides, methyl α-[(acetyl-L-alanyl)amino]isobutanoate (Ac-L-Ala-Aib-OMe, 3) and tert-butyl α-{[(benzyloxycarbonyl)amino]isobutanoyl}-L-alaninate (Z-Aib-L-Ala-OtBu, 4) are described. In the asymmetric unit of all four compounds two independent molecules were found. In all cases but one (molecule A of 3) the Aib residue is folded, the sets of Φ, ψ (or Φ, ψT) torsion angles falling in the region of the conformational energy map where both α- and 310-helices are found. A correlating statistical analysis of bond lengths, bond angles, and torsion angles from available crystal structures of 20 Aib derivatives and 11 Aib-containing linear dipeptides was also performed to obtain precise information on the geometry and conformation of the Aib residue without the influence of the constraints imposed by the intramolecular hydrogen bonds characterizing higher-order folded and helical peptides.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198719870872
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  • 2
    Electronic Resource
    Electronic Resource
    Molecular and Crystal Structures of Two Terminally Blocked Tripeptides Corresponding to the 3-5 Sequence of the Peptaibol Antibiotics Antiamoebins (1989)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1989 (1989), S. 337-343 
    Details
    ISSN: 0170-2041
    Keywords: Tripeptides ; α-Aminoisobutyric acid ; Peptide antibiotics ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Molekül- und Kristallstrukturen zweier terminal geschützter Tripeptide mit der Sequenz 3-5 der Antiamoebin-Peptaibol-AntibiotikaDie Molekül- und Kristallstrukturen der terminal geschützten Tripeptide α-[(Acetyl-α-aminoisobutanoyl-α-aminoisobutanoyl)-amino]iso-buttersäure-methylester-trihydrat [Ac-(Aib)3-OMe ⋅ 3 H2O, (1)] und α-[(Acetyl-α-aminoisobutanoyl-α-aminoisobutanoyl)amino]-(R)-sec-buttersäure-methylester-monohydrat [Ac-(Aib)2-(R)-Iva-OMe ⋅ H2O, (2)] mit den Sequenzen 3-5 der Antiamoebin-Peptaibol-Antibiotika wurden mittels Röntgen-Diffraktion bestimmt. Während das Peptid 1 in der üblichen β-Turn-Konformation vom Typ III (III′) gefaltet ist, bildet 2 einen für eine Aib-Aib-Sequenz ungewöhnlichen β-Turn vom Typ II. Laut Berechnung ist die Energie letzterer Struktur für ein isoliertes Molekül Ac-(Aib)2-(R)-Iva-OMe wesentlich höher (ΔE 〉 10 kcal/mol) als diejenige der energetisch günstigsten Konformation.
    Notes: The molecular and crystal structures of the terminally blocked tripeptides methyl α-[(acetyl-α-aminoisobutanoyl-α-aminoisobutanoyl)amino]isobutanoate trihydrate [Ac-(Aib)3-OMe ⋅ 3 H2O, (1)] and methyl α-[(acetyl-α-aminoisobutanoyl-α-aminoisobutanoyl)amino]-(R)-sec-butanoate monohydrate [Ac-(Aib)2-(R)-Iva-OMe ⋅ H2O, (2)], representing the 3-5 sequence of the peptaibol antibiotics antiamoebins, were determined by X-ray diffraction. While peptide 1 is folded in the common type-III (III′) β-bend conformation, peptide 2 forms a type-II β-bend, an unusual observation for an -Aib-Aib- sequence. A conformational energy computation analysis showed that the energy of this latter structure for an isolated Ac-(Aib)2-(R)-Iva-OMe molecule is significantly higher (ΔE 〉 10 kcal/mol) than that of the lowest-energy conformation.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198919890159
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular and crystal structures of three monothiated analogues of the terminally blocked ala-aib-ala sequence of peptaibol antibiotics (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 747-761 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular and crystal structures of three monothiated analogues of the blocked L-Ala-Aib-L-Ala sequence of peptaibol antibiotics, t-Boc-L-Ala-Aib-ψ(CSNH)-L-Ala-OMe, Ac-L-Ala-Aib-ψ(CSNH)-L-Ala-OMe, and Ac-ψ(CSNH)-L-Ala-Aib-L-Ala-OMe, determined by x-ray diffraction analyses, are reported. In all cases the peptide chain is folded with ϕ,ψ angles close to or slightly distorted from those expected for a type II β-bend conformation. However, the 4 → 1 H-bond distance falls within the accepted limits only for Ac-L-Ala-Aib-ψ(CSNH)-L-Ala-OMe. The structures are compared with those already published for their two oxygenated analogues.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360270504
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  • 4
    Electronic Resource
    Electronic Resource
    Vibrational circular dichroism of polypeptides, V. A study of 310-helical-octapeptides (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 79-89 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have measured vibrational CD spectra in the 3600-1250 cm-1 region of two monodisperse, protected octapeptides, which form right-handed 310-helices in CDC13 solution. The spectra are similar in sign pattern to those obtained for right-handed α-helices in solution but are smaller in magnitude and, additionally, provide evidence of some line-shape differences. The delineation of this type of ordered conformation was accomplished by means of 1H-nmr. Such a solution structure is consistent with the x-ray crystal structure of one of these molecules.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250107
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  • 5
    Electronic Resource
    Electronic Resource
    Self-association and solubility of peptides: Solvent-titration study of Nα-protected C-terminal sequences of substance PThis is part 136 of the Linear Oligopeptides series. For part 135, see Bismara, C., Bonora, G.M., Toniolo, C., Becker, E.L., and Freer, R.J. (1985) Int. J. Pept. Protein Res. (in press). (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 281-289 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Self-association of Nα-protected peptides related to C-terminal sequences of substance P in methylene chloride was disrupted by adding increasing amounts of various polar organic solvents. This process was monitored by the disappearance of the amide I C=O stretching band (1630 cm-1) of strongly intermolecularly H-bonded molecules in the irabsorption spectra. The effects induced by main-chain length, incorporation at position 9 of a residue promoting folding (α-aminoisobutyric acid), the nature of solvent, and peptide concentration were established. A corollary 1H-nmr investigation provided detailed information on the NH protons involved in the self-association process as H-bonding donors. The increasing propensity to aggregate exhibited by these peptides is paralleled by a decrease in their solubility. The impact of these results on the synthesis of substance P short sequences is briefly outlined.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250209
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  • 6
    Electronic Resource
    Electronic Resource
    A novel peptide conformation: First unequivocal observation of the oxy-analog of a β-bendThis paper is part 157 of the Linear Oligopeptides series; for part 156 see Ref. 1. (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 2237-2253 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The x-ray diffraction analysis of the N-benzyloxycarbonyl homo-tripeptide from α-amino-isobutyric acid has shown the occurrence of an incipient 310-helix characterized by one type-III (or type-III′) β-bend followed by one oxy-analog of the same type of β-bend. This represents the first unequivocal observation of the latter conformation, where the O - H group of the COOH moiety present at the C-terminus of the peptide main chain plays the role of the hydrogen-bonding donor. These results have been compared with those of the same peptide in its monohydrate form and of its methyl ester derivative, the x-ray diffraction structures of which are also described here.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360251203
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  • 7
    Electronic Resource
    Electronic Resource
    High-Resolution solid-state 13C-nmr of peptides: A study of chain-length dependence for 310-helix formation (1988)
    New York : Wiley-Blackwell
    Biopolymers 27 (1988), S. 1607-1617 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-resolution solid-state 13C-nmr spectra of two series of fully protected oligopeptides, Z-(Aib)n-OMe (n = 3-8) and Z-(Aib)n-L-Leu-(Aib)2-OMe (n = 0-5), were recorded to gain insight into main-chain length dependence for 310-helix formation. We found that all the oligopeptides examined adopt an incipient or a fully developed 310-helical structure, as judged from the characteristic splitting of the Cβ signals as well as the conformation-dependent displacements of the Cα and C=O peaks.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360271006
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  • 8
    Electronic Resource
    Electronic Resource
    (Cholestanyloxycarbonyl)benzyl esters as peptide substituents: Conformational properties of fully protected oligo-L-lysines with C-terminal (cholestanyloxycarbonyl)benzyl and benzyl ester moieties (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 350-358 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This study involves L-lysine oligo peptides, protected at the N-terminus by the Nps and at the ε-amino functions by Boc groups. Two series were prepared from dimer to octamer, one containing the p-[(cholestan-3β-yloxy)carbonyl]benzyl, the other one the benzyl ester group at the C-terminus. Conformational analyses were performed by IR absorption. The occurrence of the intermolecular β-structure in the solid state and in CH2Cl2 solution was demonstrated for the highest oligomers. The relative stabilities of the self-associated species were determined by adding a variety of polar solvents to the CH2Cl2 solutions. The cholestanyl-containing peptides have a lower propensity to self-aggregate than the benzyl-ester analogues. Self-aggregation and decreasing solubility run in parallel. It was also directly shown that soluble urea derivatives may disrupt intermolecular H-bonds in CH2Cl2, a point of practical interest, particularly in solid-phase peptide synthesis.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19860690214
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  • 9
    Electronic Resource
    Electronic Resource
    Konformationsübergänge zwischen enantiomeren 310-HelicesProfessor Manfred Rothe zum 60. Geburtstag gewidmet (1987)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 99 (1987), S. 1180-1182 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19870991114
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  • 10
    Electronic Resource
    Electronic Resource
    Activated Amino Acids - Structures of [α-(Phthalimido)isobutyric] Anhydride, pentachlorophenyl α-(tert-Butyloxycarbonylamino)isobutanoate, and Pentachlorophenyl α-(Benzyloxycarbonylamino)isobutanoate (1986)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1809-1822 
    Details
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Aktivierte Aminosäuren - Strukturen von [α-(Phthalimido)isobuttersäure]anhydrid, α-(tert-Butyloxycarbonylamino)isobuttersäure-pentachlorphenylester und α-(Benzyloxycarbonylamino)isobuttersäure-pentachlorphenylester[α-(Phthalimido)isobuttersäure]anhydrid [(Pht-Aib)2,O, 1] kristallisiert in der Raumgruppe P21/n mit a = 10.293(4), b = 26.511(6), c = 9.192(4) Å, β = 113.9(3)° und Z = 4 (R-Faktor für 1246 beobachtete Reflexe 0.067). Die Anhydridgruppierung ist deutlich nicht planar und besitzt die Typ-a-Konformation (trans-trans), wie sie für Monochloressigsäureanhydrid gefunden wurde. - α-(tert-Butyloxycarbonylamino)isobuttersäure-pentachlorphenylester (Boc-Aib-OPcp, 2) kristallisiert in der Raumgruppe P22/c mit a = 6.375(3), b = 32.801(6), c = 9.367(4) Å, β = 94.9(3)° und Z = 4 (R-Faktor für 1781 beobachtete Reflexe 0.0535). Die Urethangruppe ist in der für N-urethangeschützte Aib-Derivate ungewöhnlichen cis-Konformation. Die Ebene des Pentachlorphenylrings steht senkrecht auf der Ebene der Estergruppe. Die Molekule von 2 bilden Dimere, die von intermolekularen N—H…O=C(Urethan)-Wasserstoffbrückenbindungen zusammengehalten werden. - α-(Benzyloxycarbonylamino)isobuttersäure-pentachlorphenylester (Z-Aib-OPcp, 3) kristallisiert in der Raumgruppe C2/c mit a = 27.841(6), b = 6.224(3), c = 24.335(6) Å, β = 106.3(3)° und Z = 8 (R-Faktor für 2375 beobachtete Reflexe 0.047). Im Gegensatz zum Boc-Derivat 2 besitzt der aktivierte Ester 3 eine trans-Urethanbindung.
    Notes: [α-(Phthalimido)isobutyric] anhydride [(Pht-Aib)2O, 1] crystallizes in the space group P21/n with a = 10.293(4), b = 26.511(6), c = 9.192(4) Å, β = 113.9(3)°, and Z = 4 (R value for 1246 observed reflections 0.067). The anhydride moiety is significantly nonplanar and its conformation is of type a (trans-trans), as found for monochloroacetic anhydride. - α-(tert-Butyloxycarbonylamino)isobutyric acid pentachlorophenyl ester (Boc-Aib-OPcp, 2) crystallized in the space group P21/c with a = 6.375(3), b = 32.801(6), c = 9.367(4) Å, β = 94.9(3)°, and Z = 4 (R value for 1781 observed reflections 0.0535). The urethane group adopts the cis conformation, an unusual observation for a N-urethane-protected Aib derivative. The plane of the pentachlorophenyl ring is perpendicular to that of the ester group. The molecules 2 form dimers via intermolecular N—H…O=C(urethane) hydrogen bonds. - α-(Benzyloxycarbonylamino)isobutyric acid pentachlorophenyl ester (Z-Aib-OPcp, 3) crystallizes in the space group C2/c with a = 27.841(6), b = 6.224(3), c = 24.335(6) Å, β = 106.3(3)° and Z = 8 (R value for 2375 observed reflections 0.047). In contrast to the Boc derivative 2 the activated ester Z-Aib-OPcp 3 has a trans urethane bond.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.198619861101
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