Scheme 2.

Synthesis of 1. Reagents and conditions: (a) BF₃:Et₂O, 4 Å MS, CH₂Cl₂, −30 °C, 2 h, 77%; (b) 0.5 M MeONa, THF-MeOH, RT, 1 h; (c) PhCH(OMe)₂, CSA, DMF, RT, 17 h, 56% (2 steps); (d) BnBr, NaH, DMF, RT, 2 h; (e) 70% aq. TFA, CH₂Cl₂, RT, 4 h; (f) (i) Dibromantin, TEMPO, CH₃CN, RT, 2.5 h; (ii) CH₃I, NaHCO₃, DMF, RT, 16 h, 82% (4 steps); (g) TMSOTf, 4 Å MS, CH₂Cl₂, −20 °C, ~2 h, 58% (+ β-anomer 20%); (h) LiOH, H₂O₂, THF-MeOH, 16 h, 82%; (i) SO₃:C₅H₅N, C₅H₅N, 55 °C, 2 h, 76%; (j) H₂, 10% Pd/C, tBuOH-H₂O, 60 h, 100%; (k) SO₃:C₅H₅N, NaOH, RT, 16 h, 57%.