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  • 1
    Electronic Resource
    Electronic Resource
    Nucleosides. Part LVIPart LV: [1].. Aminolysis of carbamates of adenosine and cytidine (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1267-1280 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 2-(4-nitrophenyl)ethoxycarbonyl(npeoc) group, introduced 1984 as protecting group for exocyclic amino functions of nucleic-acid bases, reacts with amines under mild conditions to urea derivatives. Treatment of 2′,5′-di-O-acetyl-N6-[2-(4-nitrophenyl) ethoxycarbonyl]cordycepin (3) with NH3/MeOH overnight at room temperature affords cordycepin (4) and N6-carbamoylcordycepin (5). Preliminary investigations towards the elucidation of the reaction mechanism indicate that the aminolysis proceeds via an addition-elimination or an isocyanate mechanism, depending on the reaction conditions. The phenoxycarbonyl (phoc) group at N6 or N4 was chosen to study the mild conversion of carbamates with aromatic amines into ureas of adenosine and cytidine, respectively.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770509
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  • 2
    Electronic Resource
    Electronic Resource
    Nucleotides. Part XLVIPart XLV: [1].. The synthesis of phospholipid conjugates of antivirally active nucleosides by the improved phosphoramidite methodology (1996)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 79 (1996), S. 426-438 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of the improved phosphoramidite strategy for the synthese of oligonucleotides using β-eliminating protecting groups to phospholipid chemistry offers the possibility to synthesize phospholipid conjugates of AZT (6) and cordycepin. The synthesis of 3′-azido-3′-deoxythymidine (6) was achieved by a new isolation procedure without chromatographic purification steps in an overall yield of 50%. Protected cordycepin ( = 3′-de-oxyadenosine) derivatives, the N6,2′-bis[2-(4-nitrophenyl)ethoxycarbonyl]cordycepin (12) and the N6,5′-bis[2-(4-nitrophenyl)ethoxycarbonyl]cordycepin (13) wre prepared by known methods and direct acylation of N6-[2-(4-nitrophenyl)ethoxycarbonyl]cordycepin (9), respectively. These protected nucleosides and the 3′-azido-3′-de-oxythymidine (6) reacted with newly synthesized and properly characterized lipid-phosphoramidites 21-25, catalyzed by 1H-tetrazole, to the corresponding nucleoside-phospholipid conjugates 26-38 in high yield. The deprotection was accomplished via β-elimination with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in aprotic solvents to give analytically pure nucleoside-phospholipid diesters 39-51 as triethylammonium or sodium salts. The newly synthesized compounds were characterized by elemental analyses and UV and 1H-NMR spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19960790210
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    Paper (German National Licenses)
    Fulltext
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