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  • Organic Chemistry  (2)
  • Fullerenes  (1)
  • 1990-1994  (3)
  • 1993  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Structures and relative stabilities of silicon-containing buckminsterfullerenes: An AM1 computational study (1993)
    Springer
    Journal of cluster science 4 (1993), S. 173-183 
    Details
    ISSN: 1572-8862
    Keywords: Fullerenes ; silaballs ; heteroclusters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A computational study of 60-atom clusters having the general formula @C60-n Si n (n=1, 2, and 12) is presented. Based on total energies and calculated enthalpies of formation, the incorporation of silicon into buckminsterfullerene frameworks is destabilizing, but not prohibitively so. The synthesis of these “silaballs” by controlled pyrolysis of C6H6 mixed with compatible organosilicon compounds is considered. For the @C58Si2 system theortho (Si-Si bonded) isomer is less stable by about 40 kcal/mol than others in which the heteroatoms are separated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702717
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  • 2
    Electronic Resource
    Electronic Resource
    Carbocyclic Analogs of Nucleosides. Part 3Part 2: [1].. Synthesis of a new sulfone analog of cyclic adenosine 3′,5′-monophosphate (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 248-258 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The novel uncharged analog 2 of adenosine 3′,5′ -monophosphate (1) was prepared in its racemic form. To increase membrane permeability, the phosphate diester monoanion group of 1 was replaced by a dimethylene sulfone unit ( = methanosulfonylmethano group), and the 2′-OH group was removed. To decrease lability against acid-catalyzed depurination, the ring O-atom was replaced by a CH2 group. All three modifications are also expected to increase the stability of analog 2 towards enzymatic degradation. The carbocyclic skeleton of 2 was constructed from trinorbornenecarbaldehyde 3 (see Scheme 1-3), and the adenine precursor 6-chloropurine was introduced in the carbocyclic unit via an SN2 reaction based on Mitsunobu chemistry (Schemes 4 and 5).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760118
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  • 3
    Electronic Resource
    Electronic Resource
    Carbocyclic Analogs of Nucleosides. Part 4.Part 3: [1]. Preparation of enantiomerically pure analogs of purine nucleosides for the synthesis of sulfone-linked oligonucleotide analogs (1993)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 76 (1993), S. 826-841 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclopentane derivatives bearing a 3-(hydroxymethyl) group, a 4-(2-hydroxyethyl) functionality, and a nucleoside base are carbocyclic variants of nucleoside analogs previously described as building blocks for the preparation of oligonucleotide analogs having dimethylene sulfone (= methanosulfonylmethano) linking groups replacing the phosphodiester linking units found in natural oligonucleotides. These carbocyclic nucleoside analogs (e.g. 17 and 20) are stable to both acid-catalyzed depurination and base-catalyzed hydrolysis, in contrast with most non-ionic analogs of oligonucleotides. Furthermore, they can be prepared with complete control over the stereochemistry at the ‘anomeric’ center. A procedure is given for preparing these purine-nucleoside analogs via the construction of an enantiomerically pure carbocyclic skeleton (Schemes 1-3), followed by a Mitsunobu-type reaction to introduce the purine-base derivatives (Scheme 4). Furthermore, preliminary results for the coupling of these analogs to yield nucleoside dimers (e.g. 26) are also reported (Scheme 5).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19930760207
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