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18
Preparation of Trimer 6 (Similar for Tetramer 7)
A solution of cholic acid 2-azidoethyl ester (5, 1 mmol, 476 mg), trialkyne (0.33 mmol, 83 mg), DIPEA (0.5 mL), PPh3 (0.1 mmol, 26 mg), and CuBr (15 mg, 0.1 equiv) in 10 mL DMF was stirred at r.t. for 48 h. Then 50 mL of H2O was added to precipitate out the sticky crude product which was dried under vacuum at 40 °C. Column chromatography of the crude product on silica gel with an eluent of 4:1 EtOAc-MeOH gave 240 mg of a light yellow solid 6 in 44% yield. 1H NMR (400 MHz, CD3OD): δ = 8.06 (3 H, s), 4.71 (6 H, t, J = 4.5 Hz), 4.57 (6 H, s), 4.51 (6 H, t, J = 4.0 Hz), 3.95 (3 H, s), 3.81 (3 H, s), 3.48 (8 H, s), 3.59 (2 H, s), 3.50 (6 H, s), 3.39 (3 H, m), 2.18-2.41 (12 H, m), 1.20-2.00 (69 H, m), 1.20-2.37 (63 H, m), 0.97 (9 H, d, J = 6.4 Hz), 0.93 (9 H, s), 0.70 (9 H, s). 13C NMR (100 MHz, CD3OD): δ = 12.1, 16.7, 22.2, 23.3, 26.9, 27.7, 28.6, 30.2, 30.8, 31.1, 34.9 (2 C), 35.5, 35.7, 39.5, 40.0, 42.0, 42.3, 45.8, 46.5, 46.9, 49.5, 61.4, 62.5, 64.4, 68.0, 69.2, 71.9, 72.9, 124.4, 174.2. HRMS: m/z calcd for C92H148N9O19 [M + H]+: 1683.0886; found [M + H]+: 1683.0877.
Tetramer 7: 23% yield; mp 140 °C. 1H NMR (400 MHz, CD3OD): δ = 8.01 (4 H, s), 4.71 (8 H, t, J = 5.1 Hz), 4.55 (8 H, s), 4.51 (8 H, t, J = 5.0 Hz), 3.95 (4 H, m), 3.81 (4 H, m), 3.48 (8 H, s), 2.18-2.41 (16 H, m), 1.12-2.41 (80 H, m), 0.97 (12 H, s), 0.93 (12 H, s), 0.70 (12 H, s). 13C NMR (100 MHz, CD3OD): δ = 12.1, 16.7, 22.2, 23.3, 26.9, 27.7, 28.6, 30.2, 30.9, 31.1, 34.9 (2 C), 35.6, 35.7, 39.5, 40.0, 42.0, 42.2, 46.5, 47.0, 49.4, 62.5, 64.5, 68.0, 68.7, 69.0, 71.9, 72.9, 124.7, 174.2. HRMS: m/z calcd for C121H193N12O24 [M + H]+: 2198.4245; found [M + H]+: 2198.4170.
20
Preparation of Trimer 9
3β-Azido-cholic acid (8, 0.6 mmol, 270 mg), trialkyne (0.2 mmol, 51.8 mg), CuSO4 (0.03 mmol, 7.5 mg) and sodium ascorbate (0.12 mmol, 24 mg) were suspended in a 2:1 mixture (20 mL) of H2O and t-BuOH, and the mixture was stirred at 90 °C for 48 h. The crude product precipitated at r.t. by adding 50 mL of H2O, and was collected by centrifuga-tion. The residue was purified by column chromatography on silica gel with a 5:1:1 mixture of EtOAc-MeOH-AcOH as eluent to give a light yellow solid (175 mg, 54%). 1H NMR (400 MHz, CD3OD): δ = 8.14 (3 H, s), 4.70 (6 H, s), 4.59 (6 H, s), 4.00 (3 H, s), 3.85 (3 H, s), 3.56 (2 H, s), 3.48 (6 H, s), 3.50 (6 H, s), 3.07 (3 H, t, J = 13.1 Hz), 1.20-2.00 (69 H, m), 1.20-2.42 (69 H, m), 1.04 (9 H, d, J = 6.6 Hz), 0.89 (9 H, s), 0.74 (9 H, s). 13C NMR (100 MHz, CD3OD): δ = 12.0, 16.6, 19.5, 22.5, 23.2, 24.8, 27.0, 27.7, 28.7, 30.8, 30.9, 31.2, 32.6, 34.1, 35.1, 35.8, 37.5, 40.0, 42.0, 46.6, 47.0, 57.6, 64.3, 67.9, 69.2, 72.9, 113.6, 116.4, 175.0. HRMS: m/z calcd for C86H136N9O16 [M + H]+: 1551.0099; found [M + H]+: 1551.0133.
25
Curtius Reaction to Prepare Trimer 14
A pressure-resistant vessel equipped with a Teflon screw cap was used as the reactor. A solution of choloyl azide 10 (2.3 mmol, 1 g) in 20 mL THF was tightly sealed and stirred at 140 °C for 30 min and cooled down to r.t. Triaminoethylamine (0.77 mmol, 0.11 g) was added into the solution and then stirred at 120 °C overnight. Then THF was evaporated under vacuum. The residue was purified by column chromatography on silica gel with a 1:1 mixture of EtOAc-MeOH as eluent to yield 900 mg (80%) of a white solid product 14. 1H NMR (400 MHz, CD3OD): δ = 3.98 (3 H, s), 3.81 (3 H, s), 3.39 (3 H, m), 3.23 (3 H, m), 3.17 (6 H, t, J = 5.5 Hz), 3.10 (3 H, m), 2.58 (6 H, t, J = 5.6 Hz), 2.18-2.41 (6 H, m), 1.12-2.41 (63 H, m), 1.06 (9 H, d, J = 6.6 Hz), 0.94 (9 H, s), 0.74 (9 H, s). 13C NMR (100 MHz, CD3OD): δ = 12.1, 17.1, 22.2, 23.3, 26.9, 27.9, 28.6, 30.2, 34.1, 34.1, 34.9, 35.5, 36.5, 37.8, 38.4, 39.5, 40.0, 42.0, 42.2, 46.6, 47.5, 55.2, 68.1, 71.9, 73.0, 160.4. HRMS: m/z calcd for C78H133N16O9 [M + H]+: 1438.0435; found [M + H]+: 1438.0453.
Tetramer 15: 54% yield. 1H NMR (400 MHz, CD3OD): δ = 3.99 (4 H, s), 3.81 (4 H, s), 3.39 (4 H, m), 3.19 (8 H, t, J = 7.3 Hz), 2.33 (8 H, s), 2.23-2.37 (8 H, m), 1.12-2.30 (88 H, m), 1.08 (12 H, d, J = 6.3 Hz), 0.94 (12 H, s), 0.74 (12 H, s). 13C NMR (100 MHz, CD3OD): δ = 12.1, 17.1, 22.3, 23.3, 25.5, 26.9, 28.0, 28.6, 30.2, 34.0, 34.9 (2 C), 35.5, 36.6, 37.8, 39.0, 39.5, 40.0, 42.0, 42.2, 46.6, 47.5, 68.1, 71.9, 73.0, 160.2. HRMS: m/z calcd for C101H173N8O16 [M + H]+: 1754.2964; found [M + H]+: 1754.2938.