Ingrid 't Hart

38 Chapter 2 2 GalNAc-IV), 75.7 (C-3, GalNAc-IV), 74.5 (CH 2 , Troc), 70.8 (C-5, Gal-V), 70.8 (C-3, Gal-V), 69.3 (C-6, GalNAc-IV), 68.8 (C-2, Gal-V), 67.0 (C-4, Gal-V), 66.4 (C-5, GalNAc-IV), 61.6 (C-6, Gal-V), 55.9 (C-2, GalNAc-IV), 34.0 (CH, TDS), 24.8 (C, TDS), 20.7 (CH 3 , OAc), 20.7 (CH 3 , OAc), 20.7 (CH 3 , OAc), 20.5 (CH 3 , OAc), 20.1 (CH 3, TDS), 20.0 (CH 3, TDS), 18.6 (CH 3, TDS), 18.5 (CH 3, TDS), -1.8 (CH 3 -Si), -3.1 (CH 3 -Si). ESI HRMS (m/z): [M + NH 4 ] + calcd for C 38 H 54 Cl 3 NO 16 Si, 931.2616; found 931.2634. [α] 25/589 = 223.8° (C = 0.1; CHCl 3 ). 2,2,2-Trichloroace�midate 2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl-(1 → 3)-4,6-O- benzylidene-2-[(2,2,2-trichloromethoxy)carbonylamino]-α-D-galactopyranoside (7a). HF·Pyridine (70% HF, 1.2 mL) was added to a s�rring solu�on of disaccharide 13 (1.2 g, 1.3 mmol) in pyridine (12 mL) in a plas�c round bo�om flask. A�er 2.5 h, the mixture was diluted with DCM and quenched by addi�on of sat. aq. NaHCO 3 . The organic phase was washed with sat. aq. NaHCO 3 (2 x), dried (Na 2 SO 4 ), filtered, concentrated in vacuo and 2 x co-evaporated with toluene. The obtained intermediate was dissolved in DCM, s�rred with 4 Å molecular sieves for 30 min and 2,2,2-Trichloroethyl chloroformate (615 µL, 6.14 mmol) and Cs 2 CO 3 (400 mg, 1.23 mmol) were added. A�er 3 h the reac�on mixture was concentrated in vacuo and the obtained residue was purified by silica column chromatography using Hexane:EtOAc (1:0 to 1:1 v/v) as the eluent to isolate the α-anomer of the �tle compound. (859 mg, 71 %, over 2 steps). 1 H NMR (400 MHz, CDCl 3 ) δ 8.72 (1H, s, C=NH), 7.59 – 7.47 (2H, m, Ar-H), 7.44 – 7.29 (3H, m, Ar-H), 6.67 (1H, d, J = 3.2 Hz, H-1, GalNAc-IV), 5.54 (1H, s, CH-C 6 H 5 ), 5.41 (1H, d, J = 2.8 Hz, H-4, Gal-V), 5.32 – 5.20 (2H, m, H-2, Gal-V; NHTroc), 5.02 (1H, dd, J = 10.3, 3.3 Hz, H-3, Gal-V), 4.88 (1H, d, J = 8.1 Hz, H-1, Gal-V), 4.81 (1H, d, J = 12.1 Hz, CHH, Troc), 4.63 (1H, d, J = 12.1 Hz, CHH, Troc), 4.56 (1H, dd, J = 10.9, 7.4, 3.1 Hz, H-2, GalNAc-IV), 4.46 (1H, d, J = 2.8 Hz, H-4, GalNAc-IV), 4.34 (1H, d, J = 11.9 Hz, H-6a, GalNAc-IV), 4.27 (1H, dd, J = 11.2, 3.1 Hz, H-3, GalNAc-IV), 4.22 – 3.98 (4H, m, H-6, Gal-V; H-6b, GalNAc-IV; H-5, Gal-V), 3.88 (1H, s, H-5, GalNAc-IV), 2.18 (3H, s, OAc), 2.05 (3H, s, OAc), 2.04 (3H, s, OAc), 1.99 (3H, s, OAc). 13 C NMR (101 MHz, CDCl 3 ) δ 170.2 (C, OAc), 170.0 (C, OAc), 169.9 (C, OAc), 169.6 (C, OAc), 160.2 (C=NH), 154.0 (C=O, Troc), 137.4 (C, C 6 H 5 ), 129.1, 128.2, 126.2, 101.0 (CH-C 6 H 5 ), 100.0 (C-1, Gal-V), 96.3 (C-1, GalNAc- IV), 95.4 (CCl 3 ), 74.6 (C-4, GalNAc-IV), 74.5 (CH 2 , Troc), 71.8 (C-3, GalNAc-IV), 71.3 (C-5, Gal-V), 70.8 (C-3, Gal-V), 68.9 (C-6, GalNAc-IV), 68.4 (C-2, Gal-V), 66.4 (C-4, Gal-V), 65.3 (C-5, GalNAc-IV), 60.9 (C-6, Gal-V), 49.9 (C-2, GalNAc-IV), 20.7 (CH 3 , OAc), 20.7 (CH 3 , OAc), 20.6 (CH 3 , OAc), 20.5 (CH 3 , OAc). Scheme S3 . Forma�on of disaccharide donor 7b from disaccharide 13 . O O O O TrocHN O AcO OAc AcO AcO Ph O NH CCl 3 O O O O TrocHN O AcO OAc AcO AcO OTDS O AcO OAc O TrocHN O AcO OAc AcO AcO O CCl 3 NH i) 80% HOAc 80 °C ii) Ac 2 O, Py, DMAP iii) HF·Py, Py iv) Cs 2 CO 3, DCM, 0°C,Cl 3 CCN Ph 13 7b