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  • 1
    Electronic Resource
    Electronic Resource
    [18O] Chiral phosphate in d(CpA) and d(TpA): synthesis via phosphate triesters and assignment of configuration (1985)
    s.l. : American Chemical Society
    The @journal of organic chemistry 50 (1985), S. 5314-5323 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00225a062
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  • 2
    Electronic Resource
    Electronic Resource
    Nitrenium- und Carbenium-Ionen bei Umlagerungen in 2-azabicyclischen Systemen (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 1081-1096 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Nitrenium and Carbenium Ions in Rearrangements of 2-Azabicyclic SystemsAn ionic mechanism proceeding in intimate ion pairs is suggested for the rearrangement of N-sulfonyloxy derivatives of 2-azabicyclo[2.2.1]heptane and -hept-5-ene (e.g. 9, 11 → 10, 12). 1Experiments with 18O labelled educts show partial scrambling dependend both on structure of educt and solvent.2In methanol the intermediate carbenium ions (19, 23) react to give methoxy compounds.3MINDO/3-calculations are in agreement with the experiments: aIn the saturated systems the nitrenium ion 20 is a stable intermediate.bThe optimized geometries of the rearranged carbenium ions (21, 23) are consistent with the products obtained in methanol.
    Notes: Bei der Umlagerung von N-Sulfonyloxy-Derivaten des 2-Azabicyclo[2.2.1]heptans und -hept-5-ens (z. B. 9, 11) in bicyclische Systeme mit Stickstoff als Brückenkopfatom (10, 12) sprechen folgende Befunde für einen ionischen Ablauf, der weitgehend über enge Ionenpaare erfolgt: 1Bei Versuchen mit 18O-indizierten Substanzen tritt partielles 18O-Äquilibrieren ein, das von der Struktur der Edukte und vom Lösungsmittel beeinflußt wird.2In Methanol können die intermediären Carbenium-Ionen (19, 23) als Methoxyverbindungen abgefangen werden.3MINDO/3-Rechnungen stimmen damit überein: aIm gesättigten System ist das Nitrenium-Ion 20 stabil.bDie optimierten Geometrien der umgelagerten Carbenium-Ionen (21, 23) entsprechen in beiden Systemen den durch die Abfangversuche ermittelten Strukturen.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160323
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  • 3
    Electronic Resource
    Electronic Resource
    Umlagerung von azabicyclischen Hydroxylamin-Derivaten unter Sauerstoff-Insertion (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 1107-1117 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Rearrangement with Oxygen-Insertion in Azabicyclic Hydroxylamine DerivativesN-Hydroxy-2-azabicyclo[2.2.1]hept-5-ene (1) is rearranged to the oxaazabicyclic compounds 3, 4, and 8 by the reaction with either tosyl or benzoyl chloride. The structure of 3 was proved by X-ray analysis. Experiments with [18O]tosyl chloride as well as products of the intermediate 12 with methanol are consistent with a heterolysis in the intermediate 11 formed by N-tosylation  -  in contrast to the homolytic1) Meisenheimer rearrangement.
    Notes: N-Hydroxy-2-azabicyclo[2.2.1]hept-5-en (1) wird bei der Umsetzung mit Tosyl- und Benzoylchlorid umgelagert zu den Oxaazabicyclen 3, 4 und 8. Die Struktur von 3 wurde durch Röntgenstrukturanalyse bewiesen. Versuche mit [18O]Tosylchlorid sowie die Abfangprodukte mit Methanol sprechen für eine ionische Spaltung in dem durch N-Tosylierung gebildeten Intermediären 11, im Gegensatz zum radikalischen Ablauf der sonst analogen Meisenheimer-Umlagerung.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160325
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  • 4
    Electronic Resource
    Electronic Resource
    MINDO/3-Rechnungen und PE-Untersuchungen zur Reaktionsweise von Azabicyclen (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 1097-1106 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: MINDO/3 Calculations and PE Investigations on the Mode of the Reaction of Azabicyclic CompoundsOn the basis of PE spectra as well as orbital energies and heats of formation calculated by means of the MINDO/3 method the effect of a possible interaction between the nitrogen lonepair and the π electrons in 2-azabicyclo[2.2.1]hept-5-ene (2) and its N-hydroxy derivative 4 is being discussed. MINDO/3 calculations for the corresponding nitrenium ions indicate a possible mechanism for the rearrangement reaction of the O-tosyl derivatives of 4 and for the structure of nitrenium and carbenium ions which should be intermediates for this mechanism.
    Notes: Aufgrund von PE-Spektren sowie aufgrund nach der MINDO/3-Methode berechneter Orbitalenergien und Bildungsenthalpien wird der Effekt einer möglichen Wechselwirkung zwischen dem freien Elektronenpaar des Stickstoffs und den π-Elektronen in 2-Azabicyclo[2.2.1]hept-5-en (2) und im N-Hydroxy-Derivat 4 diskutiert. MINDO/3-Rechnungen für die entsprechenden Nitrenium-Ionen geben Hinweise auf den Mechanismus der Umlagerung der O-Tosylderivate von 4 und auf die Struktur der intermediär auftretenden Nitrenium- und Carbenium-Ionen.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160324
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  • 5
    Electronic Resource
    Electronic Resource
    Phosphoramidites of Chiral (Rp)-and (Sp)-Configurated d(T[P-18O]-A): Synthesis, Configurational Assignment, and Use as Dimer Blocks in Oligonucleotide Synthesis (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 2119-2127 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The N,N-diisopropylphosphoramidites 10a and 10b of appropriately protected chiral diastereoisomers of d(T[P-18O]-A) (8a and 8b, resp.), chiral by virtue of the isotope 18O at the P-atom, have been synthesized. The 18O-isotope was incorporated by oxidation of the phosphite triester 3 with H2[18O]/I2. Separation of the diastereoisomers was accomplished by flash chromatography of the O-3′-deprotected phosphate triesters 5a/b. The absolute configuration at the chiral P-atom was deduced from the methylation products of the fully deprotected diastereoisomers 8a and 8b. Phosphinylation of 5a and 5b yielded the configurationally pure phosphoramidites 10a and 10b, respectively, which were then employed in solid-phase synthesis to yield the self-complementary oligomers d(G-A-G-T-(Rp)-[P-18O]-A-C-T-C) (13) and d(G-A-G-T-(SP)-[P-18O]-A-C-T-C) (14), respectively.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680805
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  • 6
    Electronic Resource
    Electronic Resource
    N6-(Carbamoylmethyl)-2′-deoxyadenosine, a rare DNA Constituent: Phosphoramidite Synthesis and Properties of Palindromic Dodecanucleotides (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1649-1660 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N6-(Carbamoylmethyl)-2′-deoxyadenosine (1), a modified nucleoside occurring in bacteriophage Mu, was synthesized by two different routes. Glycinamide was introdued by nucleophilic displacement of(2,4,6,-triisopro-pylphenyl)sulfonyloxy or ethylsulfinyl groups at C(6) of the purine moiety. Compound 1 was converted into the protected phosphoramidite 6b and employed in solid-phase synthesis of the self-complementary oligonucleotides 7-14. Replacement of 2′-deoxyadenosine by 1 led to a strong decrease of the Tm values of the oligomers d(A-T)6 (7) and d(A-T-G-A-A-G-C-T-T-C-A-T)(10), respectively. As the oligemer 10 contains the recognition site d(A-A-G-C-T-T) of the endodeoxyribonuclease Hind III, it was subjected to sequence-specific hydrolysis experiments. Replacement of the first or second Ad by 1 prevented enzymatic phosphodiester hydrolysis (results with 11 and 12). In contrast, slow hydrolysis was observed if the less bulky N6-methyl-2′-deoxyadenosine replaced the second Ad residue (results with 14).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700622
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