Synthesis of Pentasaccharide Donor 17a
aReagents and conditions: (a) trifluoroacetic acid (TFA)/H2O (4:1), 0 °C, 95%; (b) NaOH (20% aq), nBu4NBr, BnBr, DCM, 23 °C, 83%; (c) 14, t-BuOK, DMSO, 23 °C, 94%; (d) 13, NIS/TfOH, MeCN, 23 °C, 63% (55% β + 8% α); (e) H2-activated [Ir(COD)(PMePh2)2]-PF6, THF, 23 °C, 91%; (f) 16, NIS/TfOH, MeCN, 23 °C, 51%; (g) levulinic acid, DCC, DMAP, DCM, 23 °C, 85%; (h) TFA/H2O (4:1), 0 °C; (i) Ac2O, TEA, DMAP, DCM, 0 °C; and (j) NH2NH2 H2O, allyl alcohol, 75% (over 3 steps from 19).