Ingrid 't Hart

47 Chemoenzyma�c synthesis of DSGb5 2 eluent to give compound 16c as an oil. The β-anomer of the �tle pentasaccharide (62 mg, 42%). 1 H NMR (400 MHz, CDCl 3 ) δ 7.61 – 6.95 (50H, m, Ar-H), 5.47 (1H, s, CH-C 6 H 5 ), 5.37 (1H, d, J = 3.1 Hz), 5.20 – 5.11 (3H, m), 5.00 (1H, d, J = 11.2 Hz), 4.94 – 4.41 (19H, m, H-1, Gal-III; H-1, Gal-V; H-1, GalNAc-IV; H-1, Gal-II), 4.40 – 3.63 (24H, m, H-1, Glc-I), 3.62 – 3.08 (10H, m), 2.91 (1H, s), 2.15 (3H, s, OAc), 2.06 (3H, s, OAc), 2.01 (3H, s, OAc), 1.96 (3H, s, OAc), 1.67 – 1.43 (4H, m, 2x CH 2 , pentyl), 1.39 – 1.19 (2H, m, CH 2 , pentyl), 0.97 – 0.92 (18H, m, 2x t-Bu). 13 C NMR (101 MHz, CDCl 3 ) δ 170.3, 170.1, 169.3, 153.6, 139.5, 139.5, 138.6, 138.5, 138.4, 138.3, 138.1, 138.1, 138.0, 137.9, 137.8, 133.8, 129.1, 129.0, 128.5, 128.5, 128.4, 128.3, 128.2, 128.2, 128.0, 127.9, 127.8, 127.7, 127.6, 127.5, 127.4, 126.5, 125.5, 125.3, 111.9, 103.5 (C-1, Glc-I), 102.9 (C-1, Gal-II), 101.5 (C-1, Gal-V), 101.3 (C-1, GalNAc-IV), 100.7 (CH-C 6 H 5 ), 99.5 (C-1, Gal-III), 95.3, 88.0, 81.7, 81.6, 81.2, 79.3, 78.7, 77.2, 76.8, 76.2, 75.9, 75.5, 75.0, 74.9, 74.2, 74.2, 73.9, 73.4, 73.2, 73.1, 72.1, 70.8, 69.7, 68.9, 68.6, 68.4, 67.7, 67.5, 67.1, 67.0, 67.0, 66.0, 61.4, 57.4, 53.8, 53.4, 50.5, 50.2, 47.1, 46.2, 29.7, 29.4, 27.5 (CH 3 , t-Bu), 27.4 (CH 3 , t-Bu), 23.4, 23.3 (C, t-Bu), 20.8 (C, t-Bu), 20.8 (CH 3 , OAc), 20.7 (CH 3 , OAc), 20.6 (CH 3 , OAc), 20.5 (CH 3 , OAc). [α] 25/589 = -84° (C = 0.01; CHCl 3 ). β-D-Galactopyranosyl-(1 → 3)-2-acetamido-2-deoxy-β-D-galactopyranosyl-(1 → 3)- α-D-galactopyranosyl-(14)-β-D-galactopyranosyl-(1 → 4)-α/β-D-glucopyranose (4a). Pentasaccharide 16a was deprotected in a total of six steps, all steps were monitored by TLC and MALDI-TOF-MS. HF·Pyridine (300 µL of 70%) was added to a mixture of compound 16a (590 mg, 0.28 mmol) in pyridine (6 mL). The mixture was s�rred at RT overnight, diluted with EtOAc, washed with sat. aq. NaHCO 3 (3 x), dried (Na 2 SO 4 ), filtered and concentrated in vacuo . The obtained crude was co-evaporated with toluene (3 x) and dissolved in THF (10 mL). To this mixture 1 M NaOH (10 mL) was added and a�er hea�ng to refluxed (80 °C) overnight, the mixture was concentrated in vacuo and co-evaporated with toluene (2 x). The resul�ng intermediate was dissolved in pyridine (10 mL) and Ac 2 O (8 mL) was added. The mixture was s�rred at RT for 6 h, diluted with EA, washed with 1 M HCl, H 2 O, sat. aq. NaHCO 3 (4 x), dried (Na 2 SO 4 ), filtered and concentrated in vacuo . The obtained residue was purified by silica column chromatography using Hexane:EtOAc (1:0 to 1:4 v/v) as the eluent to obtain the intermediate product (417 mg, 76 % over 3 steps). Ammonium cerium(IV) nitrate (587 mg, 1.07 mmol) was added to a solu�on of this intermediate in CH 3 CN (10 mL)/H 2 O (2.5 mL) at 0 °C. A�er 7 min the mixture was quenched by addi�on of sat. aq. NaHCO 3 . The layers were separated and the organic layer was washed with sat. aq. NaHCO 3 (2x), H 2 O, dried (Na 2 SO 4 ), filtered and concentrated in vacuo . The obtained crude was dissolved in MeOH (3 mL), freshly prepared NaOMe was added and the mixture was s�rred at r.t for 2 h. The mixture was neutralized with Dowex H + resin, filtered, concentrated in vacuo . The crude intermediate was dissolved in a mixture of MeOH/H 2 O/HOAc (3/3/1 mL), followed by the addi�on of Pd(OH) 2 /C (560 mg, 20 %, Degussa type) and the reac�on mixture was le� s�rring overnight under the atmosphere of hydrogen. The mixture was filtered over a pad of Celite, concentrated in vacuo and purified by Bio-Gel P-2 size exclusion chromatography O HO OH O AcHN O HO OH HO OH O HO OH O HO O O OH HO OH O O OH HO OH OH