Synthesis of C-Glycoside
679
THF (15 mL) under an atmosphere of argon. The mixture was warmed to rt and stirred
for an additional 1 h. At that time the solution was cooled to 0°C and treated with a
mixture of 3N NaOH (2.5 mL) and 30% aqueous H2O2 (2.5 mL) for 30 min. The
mixture was diluted with ether, washed with satd aq NaHCO3 and brine, dried
(Na2SO4), filtered and concentrated under reduced pressure. FCC of the residue
afforded a mixture of 21 and 22 (264 mg, ca. ratio 5:1, 84%) which had identical TLC
mobilities (Rf = 0.25, 10% EtOAc/petroleum ether). For characterization purposes, a
pure sample of 21 was obtained by resubjecting this material to a second chroma-
tography and collection of a later eluting fraction. Compound 21 was isolated as a
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colorless oil; H NMR (300 MHz, CDCl3) d 1.07 [s, 9H, (CH3)3CSi], 1.29, 1.46 [both
s, 3H ea, C(CH3)2], 1.51 (m, 1H, H-1’a), 1.75 (m, 1H, H-1’b), 2.05 (m, 1H, H-4), 3.00
(bs, 1H, D2O ex), 3.32 (m, 1H), 3.37 (s, 3H), 3.41 (m, 1H), 3.55 (m, 2H), 3.60–3.95
(m, 7H), 4.12 (m, 1H), 4.44 (s, 2H), 4.65–4.85 (m, 4H), 5.03 (d, J = 12.0 Hz, 1H),
7.26–7.78 (m, 25H); 13C NMR (75 MHz, CDCl3) d 27.7 (CH3)3CSi, C(CH3)2, 1C),
28.8 [C(CH3)2, 1C], 33.1 (C-1’), 40.5 (C-4), 55.9 (OCH3), 65.4 (C-7’), 71.4, 72.4, 73.5,
74.0, 74.6, 75.5, 76.6, 78.8, 81.2, 82.6 (12C, C-2, 3, 5, 6, 2’, 3’, 4’, 5’ 6’, 3 ꢂ PhCH2),
99.0 (C-1), 109.5 [C(CH3)2], 128.1–139.1 (Ph). HRMS (FAB) m/z calcd for
C54H66O10SiNa [M + Na]+ 925.4321. Found 925.4323. Compound 22 was character-
ized as triol 24 and triacetate 26 (vide infra).
Methyl 4-C-(2,6-anhydro-7-O-tert-butyldiphenylsilyl-1-deoxy-D-glycero-
D-manno-heptitol-1-C-yl)-2,3,6-tri-O-benzyl-4-deoxy- -D-glucopyranoside (23) and
Methyl 4-C-(2,6-anhydro-7-O-tert-butyldiphenylsilyl-1-deoxy-D-glycero-D-allo-hepti-
tol-1-C-yl)-2,3,6-tri-O-benzyl-4-deoxy- -D-glucopyranoside (24).
To a portion of
the mixture of 21 and 22 from the previous step (103 mg, 0.11 mmol) in dry methanol
was added a 1 M solution of HCl in ether (0.7 mL). The reaction was stirred for 1.5
h and then neutralized with a solution of NaOMe in methanol. Removal of the volatiles
followed by FCC of the residue provided triols 23 (65 mg, 66%) and 24 (12 mg, 12%).
Compound 23 was isolated as a clear gum; Rf = 0.50 (50% EtOAc/petroleum ether);
1H NMR (300 MHz, C6D6) d 1.18 [s, 9H, (CH3)3CSi], 1.82 (m, 1H, H-1’a), 1.98 (m,
1H, H-1’b), 2.32 (m, 1H, H-4), 2.75 (s, 1H, D2O ex, OH), 2.92 (s, 1H, D2O ex, OH),
3.22 (s, 3H, OCH3), 3.51 (s, 1H, D2O ex, OH), 3.52 (dd, J = 3.3, 9.9 Hz, partially
hidden by s at d 3.51, 1H), 3.60 (dd, J = 2.6, 8.4 Hz, 1H), 3.72 (m, 2H), 3.82 (m, 4H),
3.93 (dd, J = 6.3, 9.3 Hz, 1H), 4.01 (t, J = 9.6 Hz, 1H), 4.09 (bs, 1H), 4.26 (t, J = 6.2
Hz, 1H), 4.44 (ABq, Dd = 0.06 ppm, J = 11.7 Hz, 1H), 4.49 (ABq, Dd = 0.05 ppm,
J = 12.4 Hz, 1H), 4.74 (d, J = 3.3 Hz, 1H, H-1), 4.87 (ABq, Dd = 0.41 ppm, J = 10.6
Hz, 1H), 7.10–7.76 (m, 25H); 13C NMR (75 MHz, CDCl3) d 27.2 (CH3)3CSi], 33.4 (C-
1’), 40.0 (C-4), 55.4 (OCH3), 62.9 (C-7’), 69.0, 69.1, 70.8, 72.0, 72.9, 73.6, 73.7, 73.8,
74.4, 76.5, 81.3, 82.2, (12C, C-2, 3, 5, 6, 2’, 3’, 4’ 5’ 6’, 3 ꢂ PhCH2), 98.4 (C-1),
127.6–138.4 (Ph). HRMS (FAB) m/z calcd for C51H62O10NaSi [M + N]+ 885.4010.
Found 885.4013.
Compound 24 was isolated as a clear gum; Rf = 0.64 (50% EtOAc/petroleum
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ether); H NMR (500 MHz, C6D6) d 1.16 [s, 9H, (CH3)3CSi], 1.68 (m, 1H, H-1’a), 2.20
(m, 1H, H-1’b), 2.42 (m, 1H, H-4), 2.44 (bs, 1H, D2O ex, OH), 2.58 (d, J = 7.5 Hz, 1H,
D2O ex, OH), 2.93 (d, J = 5.5 Hz, 1H, D2O ex, OH), 3.07 (t, J = 7.3 Hz, 1H), 3.18 (s,
3H, OCH3), 3.60 (m, 3H), 3.80 (m, 3H), 3.88–4.00 (m, 4H), 4.04 (dd, J = 4.5, 11.0 Hz,
1H), 4.42 (ABq, J = 12.0 Hz, Dd = 0.05 ppm, 2H, PhCH2), 4.48 (ABq, Dd = 0.04 ppm,
J = 12.0 Hz, 2H, PhCH2), 4.76 (d, J = 3.0 Hz, 1H, H-1), 4.89 (ABq, Dd = 0.44 ppm,