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Keywords:

  • asymmetric synthesis;
  • C-glycosides;
  • mannopyranosides;
  • protecting groups;
  • stereoelectronic effects

The reported physical data in reference [25] are from a by-product. The physical data for compound 3 are the following:

TLC (petroleum ether/ethyl acetate 1:1): Rf=0.20; [α]D=−13.8 (c=1.1, chloroform); 1H NMR (250 MHz, CDCl3): δ=0.12 (s, 3 H), 0.15 (s, 3 H), 0.83 (s, 6 H), 0.85 (s, 3 H), 0.88 (s, 3 H), 1.61 (sept, 6.8 Hz, 1 H), 1.96 (s, 3 H), 3.21 (dt, J=10.3, 7.8 Hz, 1 H), 3.53 (m, 1 H), 3.60 (dd, J=9.5, 8.3 Hz, 1 H), 3.70 (m, 2 H), 3.81 (s, 3 H), 3.90 (dd, J=10.3, 8.3 Hz, 1 H), 4.17 (dd, J=12.8, 5.8 Hz, 1 H), 4.27 (dd, J=12.8, 9.5 Hz, 1 H), 4.51 (s, 2 H), 5.06 (d, J=8.0 Hz, 1 H), 5.19 (m, 2 H), 5.65 (d, J=7.8 Hz, 1 H), 5.90 (m, 1 H), 6.88 (d, J=8.5 Hz, 2 H), 7.26 ppm (d, J=8.5 Hz, 2 H); 13C NMR (62.5 MHz, CDCl3): δ=−3.53, −1.82, 18.52, 20.04, 23.61, 24.77, 34.03, 55.26, 59.19, 70.61, 72.96, 73.19, 73.34, 73.62, 80.28, 94.89, 113.84, 116.94, 129.29, 129.95, 135.16, 159.28, 170.10 ppm.

Furthermore, the desilylation step c in the transformation of compound 7 to 6 requires addition of acetic acid to be successful.

  • 1
    Angew. Chem. Int. Ed. 2002, 41, 2972–2974, DOI: 10.1002/1521-3773(20020816)41:16<2972::AID-ANIE2972>3.0.CO;2-4