Fluorous tag-assisted synthesis of complex oligosaccharides by the Boons group.55,56 Part A: Reagents and conditions (a) HO(CH2)5NH2, NaHCO3, H2O/THF (4/1, v/v), rt, 1 h, 86%; (b) Ac2O, DMAP, THF, rt, 1 h; (c) NaH, BnBr, DMF, rt, 12 h; (d) MeONa, MeOH, rt, 2 h, 80% for three steps; (e) TfOH, tol/Dioxane (1/3, v/v), rt, 15 min, (75%, α/β = 3/1); (f) TEA/DCM (1/4), rt, 4 h, 100%; (g) TfOH, DCM, −20 °C, 15 min, (72%, α only); (h) AcOH, NH2NH2, DCM/MeOH (1/1, v/v), rt, 2 h, 86%; (i) py.SO3, DMF, rt, 5 h, 75%; (j) LiOH, H2O2, THF, rt, 18 h, 82%; (k) 1M PMe3, 0.1M NaOH, THF, rt, 5 h, 78%; (l) py.SO3, TEA, 0.1M NaOH, MeOH, CF3CH2OH, 0 °C → rt, 18 h, 87% or/Ac2O, MeOH, TEA, 0 °C → rt, 1 h, 886%; (m) Pd/C, H2, MeOH/H2O (1/1, v/v), 0.1% AcOH, rt, 12 h; (n) Pd(OH)2/C, H2, H2O, 0.1% AcOH, rt, 12 h. Part B: Reagents and conditions (a) NIS, TfOH, DCM, −25 °C, 30 min, 89%; (b) DDQ, DCM : H2O =10 : 1, rt, 2 h, 82%; (c) Tf2O, TMB, DTBMP, −40 °C → rt, then 10% TFA in DCM, rt, 1 h; 87%, α only; (d) TfOH, DCM, −25 °C → rt, 3 h,71%, α : β > 20 : 1; (e) DDQ, DCM : H2O =10 : 1, rt, 2 h, 77%; (f) Tf2O, TMB, DTBMP, −40 °C → rt, then 10% TFA in DCM, rt, 1 h, 67%, α only (tetrasaccharide); (g) TfOH, DTBMP, DCM, −60 °C → rt, 18 h, then 10% TFA in DCM, rt,1 h, 76%, α only (pentasaccharide); (h) Ac2O, pyridine, DMAP, rt, 4 h; (i) NH2NH2–AcOH, pyridine, rt,1 h; (j) TMSOTf, DCM, −25 °C → rt, 1 h, 51% over three steps (hexasaccharide); (k) H2, Pd/C, AcOH, MeOH, rt, 24 h, then MeONa, MeOH, rt, 1 h, 65%.