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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 585-590 
    ISSN: 0170-2041
    Keywords: Cyclization methods ; Neuropeptide Y ; Coupling reagents ; Cyclopeptide ; Peptide synthesis ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The short-cut analog of neuropeptide Y (NPY), NPY 1YESK-Ahx-25RHYINKITRQRY-NH2, was synthesized on the amide anchor 5-(4-aminomethyl-3,5-dimethoxyphenoxy)valeric acid (ADPV) attached to polystyrene/1% divinylbenzene by using the 9-fluorenylmethoxycarbonyl/tert-butyl (Fmoc/tBu) strategy. Side-chain-to-side-chain cyclization of residues Glu2 to Lys30 of this linear heptadecapeptide amide was carried out by using different activating reagents under high-dilution conditions of the free peptide. The use of diphenylphosphoryl azide (DPPA) with the addition of triethylamine gave the highest yield of cyclic peptide. Replacing the tertiary amine by dipotassium hydrogen phosphate as an insoluble inorganic base did not improve the cyclization. Complete cyclization was achieved within four hours by using 2-(1H-benzotriazol-1-yl) -1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU) in combination with 1-hydroxybenzotriazol (HOBt) as activating agent, but the separation from excess TBTU resulted in lower yields. Reactions were monitored by HPLC and kinetic investigations were made. The identity and purity of the final product were proven by various analytical methods including atmospheric pressure ionization mass spectrometry (API-MS). The receptor binding constant of the cyclic analog was found to be comparable to that of NPY.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 497-501 
    ISSN: 0170-2041
    Keywords: Cyclopeptides ; Cyclization of peptides ; Peptide synthesis ; Coupling reagents ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the synthesis of cyclic hexapeptides the cyclization step was examined by using different procedures for activation. Three coupling methods were tested for “head-to-tail” cyclization of the resin-cleaved peptides in solution: (1) DPPA/NaHCO3; (2) TBTU/HOBt/DIEA and (3) HBTU/HOBt/DIEA. The best results were obtained by using TBTU. Reaction rates were 5 to 70 times faster with the TBTU procedure compared to the DPPA activation and generally complete conversions to cyclopeptides were observed. The kinetics of the cyclizations under high dilution conditions were monitored by HPLC. During the synthesis of the linear peptides the formation of an aminosuccinimide was observed. This by-product was characterized by electrospray MS and NMR.
    Additional Material: 4 Ill.
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  • 3
    ISSN: 0170-2041
    Keywords: Aborycin ; Peptides ; Antibiotics ; Streptomyces griseoflavus TÜ 4072 ; HIV ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The screening for growth inhibitors against Bacillus subtilis revealed a peptide antibiotic produced by Streptomyces griseoflavus TÜ 4072. Very high yields of the antibiotic named aborycin were obtained by cultivation in a medium containing soybean meal and sucrose. Isolation from the mycelium was carried out by a combination of extraction and gel chromatography. Preparative HPLC yielded the uniform antibiotic. The structure elucidation was based on GC amino acid analysis on a chiral phase, automated Edman degradation, electrospray tandem mass spectrometry and two-dimensional NMR (TOCSY, ROESY, HSQC, HMBC). Aborycin represents a 21-peptide that is cyclized from the side chain of Asp9 to the N-terminus of Cys1. Two disulfide bonds Cys1 to Cys13 and Cys7 to Cys19 form a tricyclic structure consisting exclusively of protein amino acids. The peptide antibiotic aborycin was found to be identical with a HIV protease inhibitor isolated recently from Streptomyces SP 9440.
    Additional Material: 3 Ill.
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  • 4
    ISSN: 0570-0833
    Keywords: Antibiotics ; Peptides ; Lantibiotics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lantibiotics are polycyclic peptide antibiotics containing intrachain sulfide bridges, formed from the thioether groups of the amino acids lanthionine and β-methyllanthionine. They also contain α,β-unsaturated amino acids such as didehydroalanine and didehydroaminobutyric acid. A knowledge of the lantibiotic biosynthetic steps and the enzymes involved makes possible a gene technological construction of analogous highly modified polypeptides. To the family of lantibiotics belong nisin, an important food preservative, epidermin, a highly specific therapeutic agent against acne, a series of enzyme inhibitors, as well as immunologically interesting active peptides. Lantibiotics are produced by ribosomal synthesis, starting from inactive precursor proteins (prelantibiotics). The latter are post-translationally converted into the active peptide antibiotics through enzymic modifications. The modifying enzymes effect dehydrations at the serine and threonine residues and stereospecific additions of the cysteine thiol groups to the resulting α,β-unsaturated double bonds, which lead to the formation of several sulfide bridges. Upon subsequent proteolytic cleavage of the leader peptide, the biologically active lantibiotic is formed. Conformational analyses of the lantibiotics, as well as of their prepeptides, enables one to obtain information about the mechanism and steps of the biosynthesis. Antibodies against synthetic prepeptide sequences, and modern instrumental methods for the analysis of peptides, allow structural elucidation of the biosynthetic intermediates.
    Additional Material: 21 Ill.
    Type of Medium: Electronic Resource
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