Dihydroquinone and bis-allyl-linked recyclable anomeric heavy-fluorous tags for reducing-to-non-reducing oligosaccharide synthesis.42,43 Part A: Reagents and conditions (a) 4-tert-butoxyphenol, DEAD, PPh3, THF, reflux 1 h, 98%; (b) 95% aq TFA, rt 2 h, 97%; (c) BF3·OEt2,DCM–MeOC4F9, rt 16 h; (d) NaOMe, MeOH–MeOC4F9, rt 30 min; (e) PhCH(OMe)2, CSA, MeCN–MeOC4F9, rt 1 h; (f) BnBr, NaH, 15-Crown-5, THF, rt 20 h; (g) 95% aq TFA, DCM, 0 °C, 1 h; (h) BzCl, TEA, DCM–MeOC4F9, −20 °C, 13 h, then silica-gel column chromatography, 88% from 21; (i) BF3·OEt2, DCM–MeOC4F9, rt 17 h; (j) NaOMe, MeOH–MeOC4F9, rt, 30 min; (k) n-Bu2SnO, THF, reflux, 4 h, then BnBr, TBAI, reflux 18 h; (l) Ac2O, TEA, DMAP, THF, rt, 2.5 h; (m) Pd(OH)2, H2 gas, EtOAc, rt 1 h; (n) ClAc2O, Pyr, DCM, 0 °C, 1 h; (o) ZnBr2, AcBr, DCM, rt, 20 h, then silica-gel column chromatography, 58% from 21; (p) AgOTf, AgClO3, DCM, −10 °C,16 h. Part B: Reagents and conditions (a) (i) allyl bromide, NaH, 15-crown-5, THF, rt, 16 h; (ii) 33, Hoveyda–Grubbs 2nd generation catalyst, Et2O, reflux, 18 h, 76% (2 steps); (b) NaOMe, MeOH, HFE7100, rt; 17 h, 92%; (c) BF3·OEt2, DCM, HFE7100, 0 °C, 1.5 h, 70%; (d) NaOMe, MeOH, HFE7100, rt, 18 h; (e) TrCl, TEA, THF, 40 °C, 17 h; (f) BnBr, NaH, 15-crown-5, THF, rt, 17 h; (g) CSA, CHCl3, MeOH, rt, 4 h; (h) BF3·OEt2, MS 4 Å, DCM, HFE7100, 0 °C, 1 h; (i) Pd(PPh3)4, AcOH, 80 °C, 1 h.