Compound 10 (160 mg, 0.00024 mol) was dissolved in dry MeOH (2.6 mL) and dry CH2Cl2 (1.6 mL), and NaOMe (1M, 24 μL, 24 μmol) was added. The reaction was monitored by TLC (heptane:EtOAc 1:1 and D:M 5:1). When the reaction was complete, the mixture was neutralized with Duolite C436 until pH 7, filtered and washed with MeOH. The filtered solution was concentrated under reduced pressure. The residue was purified by flash chromatography (Eluent: CH2Cl2:MeOH, 5:1) to give pure 11 (74.1 mg, 75%). 1H NMR in CDCl3 δ 4.72 (d, 2H, J=9.7 Hz, H-1, H-1′), 3.95 (br s, 2H, H-4, H-4′), 3.84 (t, 2H, J=9.8 Hz, H-2, H-2′), 3.74 (dd, 2H, J=11.47 Hz, 7.23 Hz, H-6, H-6′), 3.64 (dd, 2H, J=11.48 Hz, 4.72 Hz, H-6, H6′), 3.60-3.55 (ddd, 2H, 7.15 Hz, 4.67 Hz, 0.93 Hz, H-5, H-5′), 3.36 (dd, 2H, J=10 Hz, 3.05 Hz, H-3, H-3′).
