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  • 1
    Electronic Resource
    Electronic Resource
    Nucleophile Ringöffnung von 1-Nitro-1-cyclopropancarbonsäure-arylestern mit sterisch geschützter, aber elektronisch wirksamer Carbonyl- und Nitrogruppe. Ein neues Prinzip der Aminosäuresynthese (1990)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1990 (1990), S. 195-201 
    Details
    ISSN: 0170-2041
    Keywords: Cyclopropanes, nucleophilic ring opening of ; Pimelic acid, 6-amino-3-aza- ; β-Turns in peptides ; Peptides ; Amino acids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nucleophilic Ring Opening of Aryl 1-Nitro-1-cyclopropanecarboxylate with Sterically Protected, but Electronically Effective Carbonyl and Nitro Group. A New Principle of Amino Acid SynthesisThe readily available [2,6-di-(tert-butyl)-4-methoxyphenyl] 1-nitro-1-cyclopropanecarboxylate (4) is ring-opened by nucleophilic attack of the amino groups of (S)-α-amino acid esters (products 20-26). Reduction of the nitro group gives rise to derivatives 27-30 of 2,4-diaminobutanoic acid which are connected with a second amino acid through the nitrogen in position 4 (2-substituted 6-amino-3-azaheptanedioic acids). In two cases, these were converted into enantiomerically and diastereomerically pure Freidinger's γ-lactam dipeptides (31, 32), which have previously been shown to mimic a peptide β-turn.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199019900133
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation of Achiral and of Enantiopure Geminally Disubstituted β-Amino Acids for β-Peptide Synthesis (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1-15 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; Peptides ; Stereoselectivity ; Chirality ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---While geminally disubstituted α-amino acids are helix-inducing residues in α-peptides, gem-disubstituted β-amino acids are predicted not to fit into any of the three major secondary structures of β-peptides recognized to date [the 314 helix, the 12/10/12 helix, and the pleated sheet (Figure 1)]. In order to be able to synthesize and structurally identify β-peptides containing such building blocks, or consisting entirely of them, and in order to establish the chirality of secondary structures they may form, achiral and chiral gem-disubstituted β-amino acids must be readily available. The methods of preparation of 3-amino carboxylic acids with two carbon substituents at the 2- or 3-position (β2,2-/β3,3-amino acids, Figure 2) are reviewed. While there are numerous essentially classical routes to achiral and rac-β-amino acids of this type (Schemes 1-4), their EPC synthesis is currently the subject of investigations. These include the nucleophilic addition to (R)- or (S)-N-sulfinimines (Schemes 6-10) and other Mannich-type transformations (Schemes 19-22), stereoselective alkylations of various chiral hydropyrimidines (Schemes 11, 12, 18), of esters or amides of 2-cyano-alkanoic acids (Schemes 13, 14, 16), and of Li2 derivatives of non-racemic N-protected 3-amino-alkanoates (Scheme 17), as well as sequences of reactions involving enantiopure gem-disubstituted succinic acid derivatives and a Curtius degradation (Schemes 23-26). Oligomers of the achiral gem-disubstituted compounds 1-(aminomethyl)-cyclopropane and -cyclohexane carboxylic acid have already been shown to form 8- and 10-membered hydrogen-bonded rings, respectively (Figure 5), which provide novel motifs for the possible construction of turns, links, or steps in β-peptidic chains.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation of (R)- and (S)-2-alkyl-2-amino-3-(methylamino)propanoic and other 2,3-diaminoalkanoic acid derivatives from a chiral imidazoline (1991)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1991 (1991), S. 1323-1336 
    Details
    ISSN: 0170-2041
    Keywords: Imidazolidine, chiral, building block for amino acids ; Ethylenediamines, enantioselective synthesis of ; Carbamates, lithiated ; Cuprate Michael additions ; αβ-Diaminopropanoic acids, α-branched ; β-Lactams ; Amino acids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: t-Butyl 2-t-butyl -3-methyl-4-oxo-1-imidazolidinecarboxylate (Boc-BMI, 1) is deoxygenated (→3), reductively carboxylated (→10, 11), converted to an imidazolinedicarboxylate 31 and subjected to a 1,2-carbonyl-group transposition (→34), The new chiral building blocks thus obtained are used to synthesize derivatives of (i) 1,2-ethylenediamines (type4-11), of diaminopropanols (8, 16- 18) via the lithiated carbamate F, (ii) of 2-alkyl-2,3-diaminopropanoic acid (20-26, 30) via the enolate H, (iii) of higher 2,3-diaminoalkanoic acids (see 32, 33) via the Michael acceptor 31, and (iv) of simple α-(methylamino) acids (type 35) via the enolate of 34. A number of free α,β-diaminocarboxylic acids with a tertiary stereogenic center in the αposition is prepared (37-39). Some of these diamino acids are cyclized to β-lactams (41-43) bearing an alkyl and a phenylsulfonylamido group in the 2-position.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.1991199101227
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