Ingrid 't Hart

46 Chapter 2 2 Para- methoxyphenyl 2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl-(1 → 3)-4,6-O- benzylidene-2-[(2,2,2-trichloromethoxy)carbonylamino]-β-D-galactopyranosyl-(1 → 3)- 2-O-benzyl-4,6-O-di-tert-butyl-silanediyl-α-D-galactopyranosyl-(1 → 4)-2,3,6-tri-O- benzyl-β-D-galactopyranosyl-(1 → 4)-2,3,6-tri-O-benzyl-β-D-glucopyranoside (16a). A mixture of acceptor 8a (987 mg, 0.71 mmol), donor 7a (845 mg, 0.92 mmol) and 4 Å molecular sieves was s�rred in DCM (9 mL) for 1 h. The mixture was cooled to -35°C and TMSOTf (26 µL, 0.14 mmol) was added. A�er 5 min the reac�on was quenched by addi�on of Et 3 N. The mixture was filtered over Celite and concentrated in vacuo. The obtained residue was purified by silica gel chromatography using Toluene:EtOAc (1:0 to 8:2 v/v) as the eluent to give compound 16a as an oil. The β-anomer of the �tle pentasaccharide (562 mg, 37 %). (total isolated α/β yield: 59%). 1 H NMR (400 MHz, CDCl 3 ) δ 7.58 – 7.09 (40H, m, H-Ar), 7.00 (2H, d, J = 8.8 Hz, OMP), 6.78 (2H, d, J = 8.8 Hz, OMP), 5.47 (1H, s, CH-C 6 H 5 ), 5.36 (1H, s), 5.16 (1H, dd), 5.09 – 4.94 (3H, m), 4.93 – 3.95 (32H, m, 5x H-1), 3.95 – 3.70 (10H, m), 3.70 – 3.55 (3H, m), 3.53 – 3.42 (2H, m), 3.37 – 3.27 (2H, m), 2.90 (1H, s), 2.14 (3H, s, OAc), 2.06 (3H, s, OAc), 2.01 (3H, s, OAc), 1.95 (3H, s, OAc), 1.03 – 0.85 (18H, m, 2x t-Bu). 13 C NMR (101 MHz, CDCl 3 ) δ 170.3 (C, OAc), 170.1 (C, OAc), 169.4 (C, OAc), 155.2 (C, OMP), 153.7 (C=O, Troc), 151.5 (C, OMP), 139.4 (C, Ar), 138.5 (C, Ar), 138.4 (C, Ar), 138.3 (C, Ar), 138.1 (C, Ar), 138.0 (C, Ar), 137.9 (C, Ar), 129.0, 129.0, 128.5, 128.4, 128.3, 128.2, 128.1, 128.0, 127.8, 127.7, 127.7, 127.6, 127.5, 127.5, 127.4, 126.5, 125.3, 118.4 (2x CH, OMP), 114.5 (2x CH, OMP), 103.1 (C-1, Gal-II), 102.7 (C-1, Glc-I), 101.5 (C-1, Gal-V), 101.4 (C-1, GalNAc-IV), 100.8 (CH - C 6 H 5 ), 99.9 (C-1, Gal-III), 95.3 (CCl 3 ), 81.6, 81.2, 79.3, 78.9, 77.2, 75.9, 75.5, 75.3, 75.1, 74.9, 74.3, 74.2, 73.8, 73.5, 73.3, 73.1, 73.0, 72.1, 70.8, 68.9, 68.7, 68.4, 67.8, 67.5, 67.0, 66.0, 61.4, 55.6 (CH 3 , OMP), 53.7, 27.5 (CH 3 , t-Bu), 27.4 (CH 3 , t-Bu), 23.30, 20.8 (CH 3 , OAc), 20.7 (CH 3 , OAc), 20.7 (CH 3 , OAc), 20.5 (CH 3 , OAc). ESI HRMS (m/z): [M + Na] + calcd for C 112 H 130 Cl 3 NO 32 Si 2156.7309; 2156.7454 found. [α] 25/589 = 55.0° (C = 0.05; CHCl 3 ). N-(Benzyl)-benzyloxycarbonyl-5-aminopentyl 2,3,4,6-tetra-O-acetyl-β-D- galactopyranosyl-(1 → 3)-4,6-O-benzylidene-2-[(2,2,2-trichloromethoxy) carbonylamino]-β-D-galactopyranosyl-(1 → 3)-2-O-benzyl-4,6-O-di-tert-butylsilanediyl- α-D-galactopyranosyl-(1 → 4)-2,3,6-tri-O-benzyl-β-D-galactopyranosyl-(1 → 4)-2,3,6-tri- O-benzyl-β-D-glucopyranoside (16c). A mixture of acceptor 8b (100 mg, 0.063 mmol), donor 7a (75 mg, 0.082 mmol) and 4 Å molecular sieves was s�rred in DCM (9 mL) for 1 h. The mixture was cooled to -30°C and TMSOTf (2 µL, 0.013 mmol) was added. A�er 20 min the reac�on was quenched by addi�on of Et 3 N. The mixture was filtered over Celite and concentrated in vacuo . The obtained residue was purified by silica gel chromatography using Toluene:EtOAc (1:0 to 8:2 v/v) as the O O O O TrocHN O AcO OAc AcO AcO O O O O BnO O O OBn BnO OBn OMP O O OBn BnO BnO Ph Si O O O O BnO O O OBn BnO OBn O O O OBn BnO BnO Si NBnCbz O O O O TrocHN O AcO OAc AcO AcO Ph