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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 217-222 
    ISSN: 0947-3440
    Keywords: Amino acids, α-branched ; Highly hindered amides ; Hydrolysis of amino acid amides ; Anchimeric effect ; Phenylalanine, 2-ethyl-, 2-i-propyl- and 2-cyclohexylmethyl- ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiopure 5,5-disubstituted t-butyl 2-t-butyl-3-methyl-4-oxoimidazolidine-1-carboxylates readily available by diastereoselective double alkylation of the parent compound (Boc-BMI) can be converted to α-branched α-amino acids with two bulky substituents (PhCH2/Et, PhCH2/i-Pr, PhCH2/CH2C6H11) in four simple steps: hydrolysis to the amino acid amides, N-benzoylation, cleavage of the amino acid amide group, and debenzoylation (Scheme 3, products 6-10, overall yields 〉50%). This procedure constitutes an extension of the scope of amino acid synthesis from (R)- and (S)-Boc-BMI.
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  • 2
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By conventional peptide-coupling methods (C to N direction; mixed anhydride, bis(2)-oxooxazolidin-3-yl)phosphinoyl chloride (Bop-Cl), or dicyclohexylcarbodiimide (DCC), 2-amino-2-methyl-3-(methylamino)-propionic acid and 2-amino-2-ethyl-3-(methylamino)propionic acid ( = 2-amino-2-[(methylamino)methyl]butanoic acid) are incorporated in the central position of tri-, penta-, and heptapeptides (see 3-7, 21, and 22). The fragment coupling of the β -amino group of the diamino-acid moiety in a tetrapeptide led to partial epimerization, and thus, two epimeric heptapeptide derivatives were actually obtained (7 and epi-7). The final deprotection to the free heptapeptide (involving a Me3SiI cleavage of BocNH and MeOCONH, a saponification with NaOH, and HPLC purification) gave both the desired product (isopeptide 21), with the β -amino group inside the peptide backbone, and a product (peptide 22) of transpeptidation, with the α-amino group of the diamino acid incorporated and a (methylamino)methyl group as the side chain. Peptide 22 is completely converted to the isopeptide 21 by prolonged treatment with base. The heptapeptide 21 was analyzed by elaborate 2QF-COSY and NOESY NMR measurements in H2O/CD3OD at -5° (Table, Fig.); there is no indication for β -sheet or helical structures, a fact which was also confirmed by CD measurements.
    Additional Material: 1 Tab.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1185-1206 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Both enantiomers of tert-butyl 2-(tert-butyl)-5,5-dimethyl-4-oxoimidazolidine-1-carboxylate (11; Bbdmoic) were prepared from L-alanine (Schemes 1 and 2). The parent heterocycle, 2-tert-butyl-5,5-dimethylimidazolidin-4-one (12; from 2-aminoisobutyramide, H-Aib-NH2, and pivalaldehyde) was also available in both enantiomeric forms by resolution with O,O′-dibenzoyltartaric acid. The compound (R)- or (S)-11 was used as an auxiliary, but also as a chiral Aib building block in a dipeptide synthesis. The 3-propanoyl derivative 13 of (R)-11 was used for the preparation of enantiomerically pure 2-methyl-3-phenylpropanoic acid (enantiomer ratio (e.r.) 99.5:0.5), by benzylation of the Zn-enolate (→ 14; Scheme 3). Oxidative coupling of the bis-enolate derived from heptanedioic acid and (S)-11 (→ 23) and methanolysis of the auxiliary gave dimethyl trans-cyclopentane-1,2-dicarboxylate (26) with an e.r. of 93:7 (Scheme 5, Fig. 5). The 3-(Boc-Gly)-Bbdmoic derivative 29 was doubly deprotonated and, after addition of ZnBr2 alkylated with alkyl, benzyl, or allyl halides to give the higher amino-acid derivatives with excellent selectivities (e.r. 〉 99.5:0.5, Schemes 6 and 7). Michael additions of cuprates to [(E)-MeCH=CHCO]-Bbdmoic 36 occurred in high yields, but high diastereoselectivities were only observed with aryl cuprates (diastereoisomer ratio (d.r.) 99:1 for R = Ph, Scheme 8). Finally, 3-(Boc-CH2)-Bbdmoic 17 was alkylated through the ester Li-enolate with primary and secondary alkyl, allyl, and benzyl halides with diastereoselectivities (ds) ranging from 91 to 98%, giving acetals of Boc-Aib-Xxx-O(t-Bu) dipeptides (Scheme 4). The effectiveness of Bbdmoic is compared with that of other chiral auxiliaries previously used for the same types of transformations.
    Additional Material: 5 Ill.
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potentiometric study of the complexation of 1,4,7-triazacyclononane-l-acetic acid (1) with Cu2+ (I = 0.5 (KNO3), T = 25°) indicates the presence of the species [Cu(1)], [Cu(1)OH], [Cu(1)2], and [(Cu(1))2OH], the stability constants of which are determined. The two complexes [Cu(1)]ClO4 and [(Cu(1)2)OH]ClO4 were also characterized by X-ray structure analysis. In both cases, the Cu2+ ion is in a distorted square-pyramidal arrangement, penta-coordinated by the three N-atoms of the macrocycle, an O-atom of the carboxylate, and an additional O-atom either from a second carboxylate or from an OH-, acting as a bridge between two metal centres.
    Additional Material: 3 Ill.
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  • 5
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The first topic to be treated in this paper is the nonradioactive DNA fingerprinting by means of in-gel hybridization with digoxigenated (CAC)5. Besides the fact that timeconsuming Southern blotting can be avoided, the dried agarose is an excellent matrix to produce background-free nonradioactive DNA fingerprints. There is no tendency of either the oligonucleotide probe or the antibody towards unspecific binding to the dried agarose. Prehybridization and blocking steps are therefore superfluous. Furthermore, we will discuss what effect the degree of crosslinking of the antibodyenzyme conjugates has. The second topic concerns the isolation and characterization of locus-specific probes from a human (CAC)5 fingerprint. The isolation and characterization of one variable probe, by screening complete genomic libraries, is described and discussed. This probe is compared to a hypervariable single-copy probe, isolated from a size-enriched genomic library. The sequence of the repeat flanking locus-specific probe is presented and a semi-specific, adaptor-mediated polymerase chain reaction was designed to amplify (CAC)n/(GTG)n flanking sequences.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electrophoresis 12 (1991), S. 153-158 
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Mouse DNA fingerprints were obtained by HaeIII digestion of genomic DNA and ingel hybridization with the (GATA)4 oligonucleotide probe. In order to obtain locusspecific probes that hybridize with only one fragment of the (GATA)4 DNA fingerprint, a genomic library of size-selected inserts was constructed using a system of direct subcloning from the phage clones. During the cloning procedure, the phage as well as the plasmid insert DNAs changed primarily within their repetitive DNA but also within adjacent nonrepetitive sequences, as was demonstrated for several clones by in-gel hybridization with the (GATA)4 probe as well as by sequence analysis. Isolated subclones varied within their (GATA)n repeats, resulting in different insert lengths. Several “metastable” as well as stable (GATA)4-positive subclones could be isolated. Also, vector sequences were affected by alterations during the cloning process. These phenomena are discussed within the context of possible mechanisms for cloning artifacts.
    Additional Material: 5 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Plant/Operations Progress 7 (1988), S. 127-135 
    ISSN: 0278-4513
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The modeling of evaporation and dispersion from chemical spills has been an active area. The available models span the range of very simple calculational methods, for quick response at the time of accidents, to more complex transient models that predict the results of hypothesized events. Conservative assumptions are often used in all of these models in place of more accurate and more complicated computational techniques.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 211 (1882), S. 234-248 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 93 (1960), S. 2951-2965 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eine ganze Reihe von Carotinoid-Aldehyden mit 20-40 C-Atomen wurden in Naturprodukten aufgefunden, dazu Mono- und Bisdehydrolycopin.
    Additional Material: 4 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 283 (1956), S. 88-95 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Das von GLEMSER und EINERHAND als Ni3O2(OH)4 formulierte höhere Nickelhydroxyd besitzt eine ungeordnete Schichtenstruktur mit rhombisch deformierten Schichten und einem mittleren Abstand der Nickelionen, der zwischen demjenigen von Ni(OH)2 und β NiOOH liegt. Sein Homogenitätsbereich erstreckt sich bis zu der Zusammensetzung NiOOH.Die Oxydation von Nickelhydroxyd erfolgt streng topochemisch, dabei kann unter Erhaltung des Gitters die Zusammensetzung unter Umständen NiOOH werden. Nebstdem findet Kontraktion der Schichten unter Bildung der Gitter von Ni3O2(OH)4 und evtl. β NiOOH statt.Die Oxydationsprodukte von Nickelhydroxyd sind bei gleicher Zusammensetzung verschieden von den durch Oxydation von Nickelionen in alkalischem Milieu erhaltenen.
    Additional Material: 4 Ill.
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