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    Oligosaccharide analogues of polysaccharides. Part 21. Towards new cellulose I mimics: Synthesis of dialkynyl C-glucosides of peri-substituted anthraquinone
    (2001) Sl M.; Venanzi L.M.
    The bis-C-glucoside 2 has been synthesised as the first representative of a series of templated glucosides and cellooligosaccharides that mimick part of the unit cell of cellulose I. As expected, there are, at best, weakly persistent H-bonds between the two glucosyl residues in (D 6)DMSO and (D 7)DMF solution. The acetylated oct-1-ynitol 7 and deca-1,3-diynitol 12 were prepared from the gluconolactone 5 (Scheme 1). Coupling of 12 to Phi and 2-iodothiophene yielded 13 and 14, respectively, while dimerisation of the benzylated and acetylated deca-1,3-diynitols 10 and 12 afforded the bis-C-glucosyloctatetrayne 15 and the less stable 16, respectively. The 2-glucosylthiophene 17 was obtained by treating the C-silylated deca-1,3-diynitol 9 with Na 2S. Cross-coupling of (trimethylsilyl)acetylene (TMSA) with 1,8-bis(triflyloxy)-9,10-anthraquinone (20) at elevated temperature gave the dialkynylated 21; its structure was established by X-ray analysis (Scheme 2). Sequential coupling of 6 or 7 and TMSA to 20 gave the symmetric dialkyne 21, the mixed dialkynes 23 (from 6) and 25 (from 7), and the symmetric diglucoside 36 (from 7) in modest yields; a stepwise coupling to the acetylated monotriflate 28 proved advantageous. It led to the oct-1-ynitol 29 and the deca-1,3-diynitol 33 that were transformed into the triflates 30 and 34, respectively. Coupling of the triflate 34 to the oct-1-ynitol 7 gave the unsymmetric bis-C-glucoside 35; this was obtained in higher yields by coupling the triflate 30 to the deca-1,3-diynitol 12. Coupling of the bistriflate 20 with either 7 or 12 afforded the symmetric bis-C-glucosides 36 and 37, respectively. Deacetylation (KCN in MeOH) of 35-37 provided the unsymmetric bis-C-glucoside 2 and the symmetric analogues 3 and 4.