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36 Chapter 2 2 1,3,4,6-tetra-O-acetyl-2-[(2,2,2-trichloromethoxy)carbonylamino]-β-D-galacto- pyranoside (22). NaHCO 3 (23 g, 278 mmol) was added to Galactosamine·HCl (20 g, 93 mmol) in H 2 O (180 mL) and a�er 30 min 2,2,2-trichloroethyl chloroformate (15.3 mL, 111 mmol) was added. A�er overnight s�rring the white solids were filtered off, washed with H 2 O and dried under high vacuum overnight. The solids were dissolved in pyridine (100 mL) and ace�c anhydride (80 mL) was added. The reac�on mixture was s�rred for 3 h and concentrated in vacuo . The obtained oil was dissolved in DCM, washed with 1M HCl (2x), H2O, sat. aq. NaHCO 3 and dried (Na 2 SO 4 ), filtered and concentrated in vacuo to afford 22 (19 g, 40%, over two steps). ESI HRMS (m/z): [M + Na] + calcd for C 17 H 22 Cl 3 NO 11 , 544.0156; found 544.0155. [α] 25/589 = 326.1° (C = 0.1; CHCl 3 ). Dimethylthexylsilyl 3,4,6-tri-O-acetyl-2-[(2,2,2-trichloromethoxy)carbonylamino]-β-D- galactopyranoside (23). Hydrazine acetate (3.7 g, 40 mmol) was added to a solu�on of compound 22 (19 g, 36mmol) in DMF (60mL). Themixture was s�rred overnight, concentrated in vacuo , dissolved in EtOAc, washed with sat. aq. NaHCO 3 , H 2 O and dried (Na 2 SO 4 ), filtered and concentrated in vacuo . The resul�ng crudewas dissolved inDCM(80mL) and imidazole (7.4 g, 109 mmol) was added. When all imidazole was dissolved, tert -hexyldimethylsilyl chloride (8.6 mL, 44 mmol) was added. The mixture was s�rred overnight, washed with 1 M HCl, sat. aq. NaHCO 3 , dried (Na 2 SO 4 ), filtered and concentrated in vacuo . The obtained residue was purified by silica column chromatography using Toluene:EtOAc (1:0 to 6:4 v/v) as the eluent to afford 23 (17.2 g, 76%, over two steps). 1 H NMR (400 MHz, CDCl 3 ) δ 5.35 (1H, d, J = 3.2 Hz, H-4), 5.16 (1H, d, J = 9.9 Hz, H-3), 4.95 (1H, d, J = 8.3 Hz, NH), 4.84 – 4.68 (1H, m, H-1; CHH, Troc), 4.62 (1H, d, J = 11.7 Hz, CHH, Troc), 4.20 – 4.05 (2H, m, H-6), 3.89 (1H, t, J = 6.6 Hz, H-5), 3.78 (1H, dd, J = 18.4, 9.2 Hz, H-2), 2.16 (2H, s, OAc), 2.04 (3H, s, OAc), 1.99 (3H, s, OAc), 1.66 – 1.58 (1H, m, CH, TDS), 0.95 – 0.76 (12H, m, 4x CH 3 , TDS), 0.17 (3H, s, CH 3 -Si), 0.14 (3H, s, CH 3 -Si). 13 C NMR (101 MHz, CDCl 3 ) δ 170.5 (C, OAc), 170.4 (C, OAc), 170.3 (C, OAc), 154.0 (C=O, Troc), 96.4 (C-1), 95.3 (CCl 3 ), 74.5 (CH 2 , Troc), 70.7 (C-5), 69.9 (C-3), 66.9 (C-4), 61.8 (C-6), 54.7 (C- 2), 33.9 (CH, TDS), 24.8 (C, TDS), 20.7 (CH 3 , OAc), 20.6 (CH 3 , OAc), 20.6 (CH 3 , OAc), 19.9 (2x CH 3 , TDS), 18.5 (2x CH 3 , TDS), -1.9 (CH 3 -Si), -3.4 (CH 3 -Si). ESI HRMS (m/z): [M + NH 4 ] + calcd for C 23 H 38 Cl 3 NO 10 Si, 639.1669; found 639.1675. [α] 25/589 = -32.7° (C = 0.1; CHCl 3 ). Dimethylthexylsilyl 2-[(2,2,2-trichloromethoxy)carbonylamino]-β-D-galactopyrano- side (24). Freshly prepared NaOMe was added to compound 23 (17.3 g, 28 mmol) in MeOH (50 mL). A�er 2 h the reac�on was quenched by addi�on of Amberlite H + resin, filtered and concentrated in vacuo to afford 24 (13 g, 95%). This product was then used in the next step without addi�onal purifica�on. ESI HRMS (m/z): [M + Na] + calcd for C 17 H 32 Cl 3 NO 7 Si, 518.0911; found 518.0913. [α] 25/589 = -77.0° (C = 0.1; CHCl 3 ). O AcO OAc AcO TrocHN OAc O AcO OAc AcO TrocHN OTDS O HO OH HO TrocHN OTDS