3.2. Synthesis
1-Acetyl-4,6-dibromo-5-hydroxy-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranoside (
2). Following a general procedure [
20] with slight modification, dichlorotetrakis(1,1-dimethylethyl)di-
μ-hydroxyditin [
21] (6.8 mg, 0.012 mmol) was added to a solution of
1 (81.5 mg, 0.12 mmol) in methanol/CHCl
3 (0.80 mL, 5:3) at room temperature. After 12 h, the reaction mixture was diluted with ethyl acetate and passed through silica (ethyl acetate as the eluent). The eluent was concentrated under reduced pressure. Column chromatography [silica, hexanes/acetone (2:1)] followed by trituration with hexanes/acetone afforded a white solid (46.7 mg, 61%):
1H NMR (700 MHz, CD
3OD)
δ 8.54 (s, 1H), 7.50 (s, 1H), 5.38 (dd,
J = 9.0, 9.5 Hz, 1H), 5.32 (dd,
J = 8.3, 9.0 Hz, 1H), 5.22 (d,
J = 8.3 Hz, 1H), 5.08 (dd,
J = 9.5, 9.7 Hz, 1H), 3.97–3.90 (m, 1H), 3.75 (dd,
J = 1.5, 12.1 Hz, 1H), 3.65 (dd,
J = 6.9, 12.1 Hz, 1H), 2.55 (s, 3H), 2.08 (s, 3H), 2.07 (s, 3H), 2.00 (s, 3H);
13C{
1H} NMR (175 MHz, CD
3OD)
δ 171.7, 171.3, 171.2, 170.4, 148.9, 141.8, 129.6, 123.9, 120.8, 112.9, 110.9, 101.4, 100.8, 76.3, 74.6, 72.5, 70.3, 61.9, 23.6, 21.0, 20.58, 20.57; ESI-MS obsd 657.9532, calcd 657.9530 [(M + Na)
+, M = C
22H
23Br
2NO
11].
1-Acetyl-4,6-dibromo-5-(tert-butyldimethylsilyloxy)-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranoside (3). A sample of triethylamine (14.9 μL, 0.107 mmol) was added to a suspension of 2 (34.1 mg, 0.0535 mmol) and tert-butylchlorodimethylsilane (16.1 mg, 0.107 mmol) in CH2Cl2 (535 μL) at room temperature. After 18 h, trifluoroacetic acid (16.4 μL, 0.214 mmol), pyridine (4.3 μL, 0.53 mmol), and methanol (535 μL) were added. After 5 h, the reaction mixture was diluted with ethyl acetate and passed through silica (ethyl acetate as the eluent). The eluent was concentrated under reduced pressure. Column chromatography [silica, hexanes/ethyl acetate (2:3)] afforded a white solid (26.3 mg, 65%): 1H NMR (700 MHz, CDCl3) δ 8.57 (br s, 1H), 7.22 (s, 1H), 5.37 (dd, J = 8.6, 9.3 Hz, 1H), 5.32 (dd, J = 8.6, 9.3 Hz, 1H), 5.15 (dd, J = 9.3, 9.3 Hz, 1H), 4.99 (d, J = 7.8 Hz, 1H), 3.82–3.75 (m, 3H), 2.67 (br s, 1H), 2.52 (s, 3H), 2.08 (s, 3H), 2.07 (s, 3H), 2.05 (s, 3H), 1.05 (s, 9H), 0.36 (s, 3H), 0.35 (s, 3H); 13C{1H} NMR (175 MHz, CDCl3) δ 170.3, 170.0, 169.5, 167.9, 147.0, 140.9, 129.1, 122.9, 120.4, 114.4, 110.9, 104.5, 100.6, 75.0, 72.7, 70.8, 68.7, 61.4, 29.7, 26.3, 23.6, 20.9, 20.6, 19.0, -2.0; ESI-MS obsd 750.0581, calcd 750.0575 [(M + H)+, M = C28H37Br2NO11Si].
1-Acetyl-4,6-dibromo-5-hydroxy-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester (
4, from
3). Following a reported procedure [
19] with modification, (diacetoxyiodo)benzene (26.4 mg, 82 μmol) was added to a suspension of
3 (28.0 mg, 37 μmol), 2,2,6,6-tetramethylpiperidine 1-oxyl (1.7 mg, 11 μmol), and NaHCO
3 (3.1 mg, 37 μmol) in acetonitrile/H
2O (3:1, 273 μL) at room temperature. After 3 h, NaHCO
3 (6.2 mg, 74 μmol) was added. After 2 h, 2,2,6,6-tetramethylpiperidine 1-oxyl (1.2 mg, 7.7 μmol) was added. After 1.5 h, (diacetoxyiodo)benzene (12.0 mg, 37 μmol) was added. After 30 min, NaHCO
3 (15.7 mg, 0.19 mmol) and dimethyl sulfate (28.3 μL, 0.30 mmol) were added. After 4 h, the reaction mixture was diluted with ethyl acetate and passed through silica (ethyl acetate as the eluent). The eluent was concentrated under reduced pressure. The resulting residue was dissolved in THF (317 μL). Acetic acid (4.3 μL, 75 μmol) and TBAF (1.0 M in THF, 56 μL, 56 μmol) were added at room temperature. After 2 h, the reaction mixture was diluted with ethyl acetate and passed through silica (ethyl acetate as the eluent). The eluent was concentrated under reduced pressure. Column chromatography [silica, hexanes/acetone (3:2)] afforded a pale brown solid (8.2 mg, 33%): mp 202–204 °C;
1H NMR (700 MHz, CDCl
3)
δ 8.67 (br s, 1H), 7.32 (s, 1H), 6.00 (br s, 1H), 5.47–5.32 (m, 3H), 5.13 (d,
J = 6.8 Hz, 1H), 4.26 (d,
J = 9.2 Hz, 1H), 3.78 (s, 3H), 2.57 (s, 3H), 2.10 (s, 3H), 2.07 (s, 6H);
13C{
1H} NMR (175 MHz, CDCl
3)
δ 170.1, 169.3, 169.2, 167.9, 166.8, 146.2, 139.8, 128.6, 122.4, 120.0, 112.2, 108.5, 100.2, 98.2, 72.5, 71.9, 70.6, 68.8, 53.2, 23.6, 20.9, 20.64, 20.55; ESI-MS obsd 685.9469, calcd 685.9479 [(M + Na)
+, M = C
23H
23Br
2NO
12].
1-Acetyl-5-benzyloxy-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester (
7). Following a reported method [
6] with some modification, activated molecular sieves 4Å (250 mg),
5 (557 mg, 2.0 mmol),
6 (2.4 g, 6.0 mmol), and mercury(II) oxide (645 mg, 3.0 mmol) were placed in a flask and treated under argon with toluene/nitromethane (4:1, 20 mL). The resulting orange suspension was then treated with mercury(II) bromide (7.0 mg, 19 μmol), heated to 30 °C, and stirred for 12 h. The reaction was quenched by the addition of pyridine (2.0 mL). The mixture was filtered through a silica pad (2 cm × 2 cm, CH
2Cl
2/acetone 1:1). The filtrate was concentrated and subjected to column chromatography [silica, 1% to 3% acetone in CH
2Cl
2], followed by recrystallization (hexanes/CH
2Cl
2), which afforded a white solid (583 mg, 49%): mp 189–191 °C;
1H NMR (600 MHz, CDCl
3)
δ 8.31 (br s, 1H), 7.46 (d,
J = 7.3 Hz, 2H), 7.39 (t,
J = 7.7 Hz, 2H), 7.33 (t,
J = 7.3 Hz, 1H), 7.15 (br s, 1H), 7.07–7.01 (m, 2H), 5.41–5.30 (m, 3H), 5.11 (s, 2H), 5.08 (d,
J = 7.0 Hz, 1H), 4.19 (d,
J = 8.9 Hz, 1H), 3.74 (s, 3H), 2.55 (s, 3H), 2.08 (s, 3H), 2.07 (s, 3H), 2.05 (s, 3H);
13C{
1H} NMR (150 MHz, CDCl
3)
δ 170.1, 169.3, 169.1, 167.9, 166.8, 155.6, 141.1, 136.9, 128.6, 128.0, 127.5, 124.7, 117.7, 115.7, 110.6, 101.5, 100.8, 72.7, 71.7, 70.9, 70.5, 69.0, 53.1, 23.7, 20.7, 20.6, 20.5 (one expected carbon is missing); ESI-MS obsd 620.1742, calcd 620.1739 [(M + Na)
+, M = C
30H
31NO
12].
1-Acetyl-5-hydroxy-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucuronic acid methyl ester (8). A suspension of 7 (170 mg, 0.28 mmol) and Pd/C (10 wt%, 30 mg, 28 μmol) in CH2Cl2/ethanol/THF (4:1:5, 11 mL) was stirred under an atmosphere of H2 (1 atm) for 1 h. The reaction mixture was filtered through a silica pad (2 cm × 2 cm, acetone). The filtrate was concentrated and recrystallized (hexanes/CH2Cl2) to afford a white solid (106 mg, 75%): mp 200–202 °C; 1H NMR (600 MHz, CDCl3) δ 8.24 (br s, 1H), 7.10 (br s, 1H), 6.92 (d, J = 2.5 Hz, 1H), 6.89 (dd, J = 8.9, 2.5 Hz, 1H), 6.13 (s, 1H), 5.41–5.32 (m, 3H), 5.07 (d, J = 7.1 Hz, 1H), 4.22 (d, J = 9.2 Hz, 1H), 3.76 (s, 3H), 2.54 (s, 3H), 2.10 (s, 3H), 2.07 (s, 3H), 2.06 (s, 3H); 13C{1H} NMR (150 MHz, CDCl3) δ 170.2, 169.5, 169.4, 168.2, 167.0, 152.7, 141.0, 128.2, 125.0, 117.7, 115.0, 110.6, 102.9, 100.7, 72.5, 71.8, 70.9, 69.0, 53.1, 23.6, 20.7, 20.6, 20.5; ESI-MS obsd 530.1264, calcd 530.1269 [(M + Na)+, M = C23H25NO12].
1-Acetyl-4,6-dibromo-5-hydroxy-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester (
4, from
8). Following a reported method [
5] with some modification, a solution of NBS (156 mg, 0.88 mmol) in CH
2Cl
2 (10.0 mL) was added dropwise over 30 min to a solution of
8 (215 mg, 0.42 mmol) and 2,6-DTBP (92 μL, 0.42 mmol) in CH
2Cl
2 (6.0 mL) at −78 °C. The reaction mixture was allowed to warm to room temperature, stirred for 2.5 h, and quenched by the addition of 10% aqueous Na
2S
2O
3. The mixture was washed with brine, dried (Na
2SO
4), and concentrated. Column chromatography (silica, CH
2Cl
2 with 1% to 4% acetone) afforded a white solid (242 mg, 87%): the
1H NMR data were consistent with the product from
3; ESI-MS obsd 685.9489, calcd 685.9479 [(M + Na)
+, M = C
23H
23Br
2NO
12].
5-{[(1R,8S,9s)-Bicyclo [6.1.0]non-4-yn-9-yl]methoxy}-4,6-dibromo-1H-indole-3-yl β-D-glucopyranosiduronic acid methyl ester (9). In an initial procedure, diisopropyl azodicarboxylate (13 μL, 63 μmol) was added to a solution containing 4 (34 mg, 51 μmol), endo-BCN-OH (9.3 mg, 62 μmol), and PPh3 (17 mg, 65 μmol) in CH2Cl2 (0.51 mL) at room temperature. The reaction mixture was stirred for 1 h and then quenched by the addition of H2O. The organic layer was washed with brine, dried (Na2SO4), and concentrated. Column chromatography (silica, hexanes with 0% to 4% acetone) afforded the Mitsunobu coupling product (1-acetyl-5-{[(1R,8S,9s)-bicyclo [6.1.0]non-4-yn-9-yl]methoxy}-4,6-dibromo-5-hydroxy-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester) as a white solid (28 mg, 69%), which was characterized by 1H NMR spectroscopy (500 MHz, CDCl3): δ 8.71 (s, 1H), 7.35 (s, 1H), 5.47–5.31 (m, 3H), 5.14 (d, J = 7.0 Hz, 1H), 4.27 (d, J = 9.6 Hz, 1H), 4.10 (d, J = 7.8 Hz, 2H), 3.78 (s, 3H), 2.58 (s, 3H), 2.37–2.28 (m, 4H), 2.28–2.20 (m, 2H), 2.11 (s, 3H), 2.07 (s, 3H), 2.06 (s, 3H), 1.80–1.65 (m, 3H), 1.10–1.01 (m, 2H). In a subsequent procedure to directly obtain the title compound via a one-flask process, diisopropyl azodicarboxylate (3.5 μL, 0.018 mmol) was added to a solution of 4 (7.0 mg, 0.11 mmol), endo-BCN-OH (1.9 mg, 0.013 mmol), and PPh3 (4.7 mg, 0.018 mmol) in CH2Cl2 (105 μL) at room temperature. After 3 h, methanol (420 μL) and K2CO3 (1.5 mg) were added. After 1.5 h, the reaction mixture was passed through silica [CH2Cl2/methanol (2:1)]. The eluent was concentrated under reduced pressure. Preparative thin layer chromatography [silica, 0.25 mm thick, 20 cm wide × 10 cm tall, CHCl3/methanol (10:1)] afforded the title compound as a white solid (2.9 mg, 44%): 1H NMR (700 MHz, CD3OD) δ 7.50 (s, 1H), 7.12 (s, 1H), 4.82 (d, J = 8.0 Hz, 1H), 4.09 (d, J = 7.8 Hz, 2H), 3.96 (d, J = 9.6 Hz, 1H), 3.78 (s, 3H), 3.66 (dd, J = 9.4, 9.6 Hz, 1H), 3.58 (dd, J = 8.0, 8.8 Hz, 1H), 3.49 (dd, J = 8.8, 9.4 Hz, 1H), 2.34–2.22 (m, 4H), 2.22–2.13 (m, 2H), 1.78–1.65 (m, 3H), 1.09–0.98 (m, 2H); 13C{1H} NMR (175 MHz, CD3OD) δ 171.1, 147.1, 138.5, 132.9, 120.1, 116.1, 115.4, 112.7, 107.9, 105.3, 99.7, 77.4, 76.8, 75.0, 73.0, 72.8, 52.9, 30.7, 22.0, 21.8, 20.2; ESI-MS obsd 650.0000, calcd 649.9996 [(M + Na)+, M = C25H27Br2NO8].
Sodium 5-{[(1R,8S,9s)-bicyclo [6.1.0]non-4-yn-9-yl]methoxy}-4,6-dibromo-1H-indole-3-yl β-D-glucopyranosiduronate (10). Aqueous NaHCO3 (100 mM, 46 μL) was added to a solution of 9 (2.9 mg, 0.0046 mmol) in methanol (184 μL) at room temperature. The reaction mixture was heated to 40 °C for 13 h and then to 60 °C for 23 h. The reaction mixture was allowed to cool to room temperature and then concentrated under reduced pressure to afford a white solid (2.5 mg, 86%): 1H NMR (700 MHz, CD3OD) δ 7.49 (s, 1H), 7.35 (s, 1H), 4.73 (d, J = 8.1 Hz, 1H), 4.09 (d, J = 7.8 Hz, 2H), 3.68 (d, J = 9.5 Hz, 1H), 3.59 (dd, J = 8.1, 8.8 Hz, 1H), 3.56 (dd, J = 9.2, 9.5 Hz, 1H), 3.51 (dd, J = 8.8, 9.2 Hz, 1H), 2.33–2.24 (m, 4H), 2.21–2.15 (m, 2H), 1.77–1.66 (m, 3H), 1.07–0.98 (m, 2H); 13C{1H} NMR (175 MHz, CD3OD) δ 176.6, 146.8, 138.7, 132.8, 120.0, 116.3, 115.9, 112.3, 107.8, 105.2, 99.6, 77.9, 76.6, 75.1, 73.7, 72.8, 30.6, 22.0, 21.7, 20.1; ESI-MS obsd 635.9840, calcd 635.9839 [(M + H)+, M = C24H24Br2NNaO8].
1-Acetyl-5-(17-azido-3,6,9,12,15-pentaoxaheptadecyloxy)-4,6-dibromo-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester (11). A suspension of 4 (92 mg, 0.14 mmol) and K2CO3 (23 mg, 0.17 mmol) in DMF (3.1 mL) was treated with P1 (0.10 g, 0.29 mmol) and stirred overnight at room temperature. The reaction mixture was diluted with ethyl acetate (20 mL), washed with H2O (20 mL × 3) and brine (20 mL × 2), dried over anhydrous Na2SO4, and concentrated. The crude mixture was chromatographed (silica, CH2Cl2/ethyl acetate = 4:1 to 2:1) to obtain a white non-crystalline solid (58 mg, 44%): 1H NMR (500 MHz, CDCl3) δ 8.71 (s, 1H), 7.36 (s, 1H), 5.46–5.30 (m, 3H), 5.13 (d, J = 7.0 Hz, 1H), 4.26 (d, J = 9.6 Hz, 1H), 4.21–4.15 (m, 2H), 3.96 (t, J = 5.0 Hz, 2H), 3.81–3.76 (m, 5H), 3.72–3.65 (m, 16H), 3.39 (t, J = 5.1 Hz, 2H), 2.58 (s, 3H), 2.10 (s, 3H), 2.06 (s, 6H); 13C{1H} NMR (125 MHz, CDCl3) δ 170.1, 169.3, 169.1, 167.9, 166.8, 149.7, 140.1, 130.9, 123.0, 120.3, 116.2, 112.4, 107.5, 100.2, 72.5, 72.4, 71.9, 70.8, 70.68, 70.66, 70.62, 70.59, 70.58, 70.56, 70.1, 70.0, 68.8, 53.1, 50.7, 23.7, 20.9, 20.6, 20.5 (two expected carbons are missing); ESI-MS obsd 975.1123, calcd 975.1117 [(M + Na)+, M = C35H46Br2N4O17].
5-(17-Azido-3,6,9,12,15-pentaoxaheptadecyloxy)-4,6-dibromo-1H-indol-3-yl β-D-glucopyranosiduronic acid (12). A solution of 11 (15 mg, 16 μmol) in THF/methanol (1:1, 0.50 mL) was treated with aqueous NaOH (1 M, 16 μL) and stirred overnight at room temperature. The reaction mixture was concentrated and chromatographed [silica, CH2Cl2/methanol (5:1 to 2:1)] to afford a pale-yellow non-crystalline solid (9.0 mg, 74%): 1H NMR (500 MHz, CD3OD) δ 7.51 (s, 1H), 7.30 (s, 1H), 4.76 (d, J = 7.8 Hz, 1H), 4.15 (t, J = 5.0 Hz, 2H), 3.95 (t, J = 5.0 Hz, 2H), 3.81–3.77 (m, 2H), 3.75 (d, J = 9.7 Hz, 1H), 3.72–3.57 (m, 18H), 3.51 (t, J = 9.0 Hz, 1H), 3.36 (t, J = 5.1 Hz, 2H); 13C{1H} NMR (125 MHz, CD3OD) δ 175.4, 146.7, 138.6, 132.8, 119.9, 116.0, 112.1, 107.6, 105.1, 77.7, 76.6, 75.0, 73.6, 73.5, 71.6, 71.50, 71.47, 71.45, 71.42, 71.40, 71.2, 71.0, 51.7 (three expected carbons are missing); ESI-MS obsd 769.0583, calcd 769.0573 [(M − H)−, M = C26H36Br2N4O13].
1-Acetyl-4,6-dibromo-5-(1-hydroxy-3,6,9-trioxanon-9-yl)-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester (13). A sample of DIPEA (64 μL, 0.37 mmol) was added to a solution containing 4 (122 mg, 0.18 mmol) and P2 (100 mg, 0.30 mmol) in CH2Cl2 (1.0 mL) at room temperature. The reaction mixture was stirred at 35 °C for 36 h and then concentrated. Column chromatography (silica, CH2Cl2 with 0% to 70% ethyl acetate) afforded a white non-crystalline solid (116 mg, 79%): 1H NMR (600 MHz, CDCl3) δ 8.71 (s, 1H), 7.35 (s, 1H), 5.47–5.37 (m, 2H), 5.34 (t, J = 8.9 Hz, 1H), 5.13 (d, J = 7.0 Hz, 1H), 4.26 (d, J = 9.7 Hz, 1H), 4.22–4.16 (m, 2H), 4.00–3.94 (m, 2H), 3.83–3.79 (m, 2H), 3.78 (s, 3H), 3.76–3.70 (m, 4H), 3.67–3.60 (m, 2H), 2.57 (s, 3H), 2.10 (s, 3H), 2.06 (s, 6H); 13C{1H} NMR (150 MHz, CDCl3) δ 170.1, 169.3, 169.2, 167.9, 166.8, 149.7, 140.1, 130.9, 123.0, 120.3, 116.2, 112.4, 107.5, 100.2, 72.52, 72.50, 72.4, 71.9, 70.9, 70.6, 70.5, 70.2, 68.8, 61.8, 53.1, 23.7, 20.9, 20.6, 20.5; ESI-MS obsd 818.0262, calcd 818.0266 [(M + Na)+, M = C29H35Br2NO15].
1-Acetyl-4,6-dibromo-5-(1-(4-nitrophenoxycarbonyloxy)-3,6,9-trioxanon-9-yl)-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester (14). A suspension of 13 (60 mg, 75 μmol), 4-nitrophenyl chloroformate (24 mg, 0.12 mmol), and activated molecular sieves 4Å (150 mg) in anhydrous CH2Cl2 (3.0 mL) was treated with pyridine (12 μL, 0.15 mmol) and stirred at room temperature for 6 h. The crude mixture was filtered through a silica pad (2 cm × 2 cm, ethyl acetate). The filtrate was concentrated and chromatographed (silica, CH2Cl2 with 0% to 20% ethyl acetate) to afford a white non-crystalline solid (70 mg, 97%); 1H NMR (500 MHz, CDCl3) δ 8.69 (s, 1H), 8.26–8.20 (m, 2H), 7.39–7.36 (m, 2H), 7.35 (s, 1H), 5.46–5.31 (m, 3H), 5.13 (d, J = 6.9 Hz, 1H), 4.48–4.43 (m, 2H), 4.27 (d, J = 9.7 Hz, 1H), 4.22–4.16 (m, 2H), 3.97 (t, J = 4.9 Hz, 2H), 3.88–3.84 (m, 2H), 3.84–3.81 (m, 2H), 3.79–3.74 (m, 5H), 2.57 (s, 3H), 2.10 (s, 3H), 2.06 (s, 6H); 13C{1H} NMR (125 MHz, CDCl3) δ 170.1, 169.3, 169.1, 167.9, 166.8, 155.5, 152.5, 149.7, 145.3, 140.0, 130.9, 125.2, 122.9, 121.7, 120.3, 116.2, 112.3, 107.5, 100.1, 72.5, 72.4, 71.9, 70.9, 70.8, 70.6, 70.2, 68.76, 68.75, 68.4, 53.1, 23.7, 20.9, 20.6, 20.5; ESI-MS obsd 983.0317, calcd 983.0328 [(M + Na)+, M = C36H38Br2N2O19].
1-Acetyl-5-(11-aza-25-azido-3,6,9,14,17,20,23-heptaoxa-10-oxo-pentacosyloxy)-4,6-dibromo-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester (15). A solution of 14 (24 mg, 25 μmol) and P3 (12 μL, 50 μmol) in anhydrous CH2Cl2 (0.50 mL) was treated with DIPEA (8.7 μL, 50 μmol) and stirred at room temperature for 24 h. The crude mixture was concentrated and chromatographed (silica, CH2Cl2 to ethyl acetate) to afford a white non-crystalline solid (21 mg) as a mixture of 15 and 16. This sample was further purified by preparative TLC [silica, 5 mm thick, 20 cm × 20 cm, hexanes/actetone (1:1), Rf = 0.2 for 15 and 0.15 for 16]. Data for 15 (8.6 mg, 32%): 1H NMR (500 MHz, CDCl3) δ 8.72 (s, 1H), 7.36 (s, 1H), 5.46–5.28 (m, 4H), 5.13 (d, J = 7.0 Hz, 1H), 4.26 (d, J = 9.6 Hz, 1H), 4.22 (t, J = 4.8 Hz, 2H), 4.18 (t, J = 4.9 Hz, 2H), 3.96 (t, J = 5.0 Hz, 2H), 3.81–3.78 (m, 2H), 3.77 (s, 3H), 3.74–3.69 (m, 4H), 3.69–3.64 (m, 10H), 3.64–3.59 (m, 4H), 3.55 (t, J = 5.1 Hz, 2H), 3.41–3.34 (m, 4H), 2.57 (s, 3H), 2.10 (s, 3H), 2.06 (s, 3H), 2.06 (s, 3H); 13C{1H} NMR (125 MHz, CDCl3) δ 170.1, 169.3, 169.1, 167.9, 166.8, 156.5, 149.7, 140.1, 130.9, 123.0, 120.3, 116.2, 112.4, 107.5, 100.2, 72.6, 72.4, 71.9, 70.8, 70.71, 70.67, 70.62, 70.57, 70.5, 70.3, 70.2, 70.1, 70.0, 69.8, 68.8, 64.0, 53.1, 50.7, 40.8, 23.7, 20.9, 20.6, 20.5 (two expected carbons are missing); ESI-MS obsd 1084.1874, calcd 1084.1880 [(M + H)+, M = C40H55Br2N5O20]. Data for 16 (6.7 mg, 26%): 1H NMR (500 MHz, CDCl3) δ 8.23 (s, 1H), 7.48 (s, 1H), 7.14 (d, J = 2.7 Hz, 1H), 5.42–5.24 (m, 4H), 5.04 (d, J = 7.3 Hz, 1H), 4.25–4.13 (m, 5H), 3.95 (t, J = 5.1 Hz, 2H), 3.81–3.78 (m, 2H), 3.76 (s, 3H), 3.72–3.68 (m, 4H), 3.68–3.63 (m, 10H), 3.62–3.57 (m, 4H), 3.54–3.49 (m, 2H), 3.40–3.31 (m, 4H), 2.10 (s, 3H), 2.05 (s, 3H), 2.04 (s, 3H); 13C{1H} NMR (125 MHz, CDCl3) δ 170.1, 169.4, 169.3, 167.1, 156.5, 146.5, 136.6, 131.2, 119.0, 115.0, 114.7, 112.6, 106.9, 101.0, 72.6, 72.4, 72.2, 70.79, 70.76, 70.7, 70.58, 70.55, 70.5, 70.3, 70.1, 70.0, 69.7, 69.3, 64.0, 53.0, 50.7, 40.8, 21.0, 20.7, 20.5 (three expected carbons are missing); ESI-MS obsd 1042.1788, calcd 1042.1774 [(M + H)+, M = C38H53Br2N5O19].
5-(11-Aza-25-azido-3,6,9,14,17,20,23-heptaoxa-10-oxo-pentacosyloxy)-4,6-dibromo-1H-indol-3-yl β-D-glucopyranosiduronic acid (17). A solution of 15 (8.6 mg, 7.9 μmol) in CH2Cl2/methanol (1:1, 0.50 mL) was treated with aqueous NaOH (1 M, 16 μL) and stirred overnight at room temperature. The reaction mixture was concentrated and purified by preparative TLC [silica, 5 mm thick, 20 cm × 20 cm, CH2Cl2/methanol (3:2), Rf = 0.45] to afford a white non-crystalline solid (5.7 mg, 80%): 1H NMR (500 MHz, CD3OD) δ 7.50 (s, 1H), 7.35 (s, 1H), 4.74 (d, J = 7.7 Hz, 1H), 4.23–4.11 (m, 4H), 3.94 (t, J = 4.8 Hz, 2H), 3.82–3.67 (m, 8H), 3.66–3.55 (m, 15H), 3.55–3.48 (m, 3H), 3.37 (t, J = 4.8 Hz, 2H), 3.28 (t, J = 5.5 Hz, 2H); 13C{1H} NMR (125 MHz, CD3OD) δ 159.0, 146.7, 138.8, 132.8, 120.0, 116.2, 116.0, 112.0, 107.6, 105.2, 77.9, 75.1, 73.7, 73.6, 71.73, 71.68, 71.52, 71.48, 71.46, 71.3, 71.2, 71.1, 71.0, 70.7, 65.2, 51.8, 41.7 (four expected carbons are missing); ESI-MS obsd 900.1177, calcd 900.1155 [(M − H)−, M = C31H45Br2N5O16].
4,6-Dibromo-5-(1-hydroxy-3,6,9-trioxanon-9-yl)-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester (18). A solution of 13 (2.8 mg, 3.5 μmol) in methanol (60 μL) was treated with NaHCO3 (0.031 mg, 0.35 μmol). The heterogeneous reaction mixture was stirred at room temperature for 90 min. The reaction mixture was concentrated. The resulting yellow oil was chromatographed (silica, hexanes/acetone = 1:1) to obtain a yellowish green oil (2.6 mg, 98%): 1H NMR (600 MHz, CDCl3) δ 7.80 (d, J = 2.7 Hz, 1H), 7.46 (s, 1H), 7.14 (d, J = 2.7 Hz, 1H), 5.41–5.32 (m, 3H), 5.04 (d, J = 7.4 Hz, 1H), 4.19–4.14 (m, 3H), 3.99–3.95 (m, 2H), 3.83–3.80 (m, 2H), 3.78–3.73 (m, 7H), 3.67–3.63 (m, 2H), 2.10 (s, 3H), 2.05 (s, 3H), 2.05 (s, 3H); ESI-MS obsd 776.0160, calcd 776.0160 [(M + Na)+, M = C27H33Br2NO14].
4,6-Dibromo-5-(1-hydroxy-3,6,9-trioxanon-9-yl)-1H-indol-3-yl β-D-glucopyranosiduronic acid methyl ester (19). A solution of 13 (15 mg, 19 μmol) in CH2Cl2/methanol (1:4, 0.95 mL) was treated with K2CO3 (2.7 mg, 19 μmol). The heterogeneous reaction mixture was stirred at room temperature for 40 min. The reaction was then quenched by the addition of acetic acid (3.0 μL, 52 μmol). The crude mixture was filtered through a silica pad (2 cm × 2 cm, methanol). The filtrate was concentrated and chromatographed [silica, CH2Cl2/methanol (9:1)] to afford a pale-yellow non-crystalline solid (10 mg, 84%): 1H NMR (500 MHz, CD3OD) δ 7.50 (s, 1H), 7.12 (s, 1H), 4.83 (d, J = 7.7 Hz, 1H), 4.15 (t, J = 4.9 Hz, 2H), 3.99–3.91 (m, 3H), 3.82–3.76 (m, 5H), 3.71–3.63 (m, 5H), 3.62–3.55 (m, 3H), 3.49 (dd, J = 9.1 Hz, 1H); 13C{1H} NMR (125 MHz, CD3OD) δ 171.1, 146.9, 138.5, 132.9, 120.0, 116.0, 115.4, 112.3, 107.7, 105.3, 77.3, 76.8, 74.9, 73.8, 73.6, 73.0, 71.8, 71.5, 71.3, 62.3, 52.9; ESI-MS obsd 625.9881, calcd 625.9878 [(M − H)−, M = C21H27Br2NO11].
4,6-Dibromo-5-[1-hydroxy-3,6,9-trioxanon-9-yl]-1H-indol-3-yl β-D-glucopyranosiduronic acid (20). A solution of 19 (10 mg, 16 μmol) in methanol (0.64 mL) was treated with aqueous NaHCO3 (100 mM, 0.16 mL) at room temperature and then stirred at 60 °C for 18 h. The reaction mixture was allowed to cool to room temperature and then concentrated. Chromatography [silica, CH2Cl2/methanol (4:1 to 1:4)] afforded a white non-crystalline solid (8.8 mg, 90%): 1H NMR (600 MHz, CD3OD) δ 7.49 (s, 1H), 7.35 (s, 1H), 4.73 (d, J = 7.7 Hz, 1H), 4.15 (t, J = 4.8 Hz, 2H), 3.95 (t, J = 4.8 Hz, 2H), 3.83–3.78 (m, 2H), 3.72–3.65 (m, 5H), 3.62–3.54 (m, 4H), 3.51 (t, J = 9.0 Hz, 1H); 13C{1H} NMR (150 MHz, CD3OD) δ 176.6, 146.7, 138.8, 132.8, 120.0, 116.2, 116.0, 112.0, 107.6, 105.1, 77.9, 76.6, 75.1, 73.71, 73.66, 73.6, 71.7, 71.5, 71.3, 62.2; ESI-MS obsd 611.9726, calcd 611.9722 [(M − H)−, M = C20H25Br2NO11].
1-Acetyl-5-bromo-1H-indole-3-carbaldehyde (22-Br5). A sample of DMAP (38 mg, 0.31 mmol) was added to a mixture of 5-bromo-3-formylindole (21-Br5, 7.0 g, 31 mmol), acetic anhydride (5.9 mL, 62 mmol), and triethylamine (8.5 mL, 61 mmol) in CH2Cl2 (78 mL) at room temperature. The reaction mixture was stirred for 18 h and then concentrated. The resulting crude product was washed with ice-cold CH2Cl2 (15 mL) to afford a bright yellow solid (7.4 g, 89%): mp 196–198 °C; 1H NMR (700 MHz, CDCl3) δ 10.10 (s, 1H), 8.45 (d, J = 2.0 Hz, 1H), 8.30 (d, J = 8.9 Hz, 1H), 8.06 (s, 1H), 7.55 (dd, J = 8.8, 2.1 Hz, 1H), 2.74 (s, 3H); 13C{1H} NMR (175 MHz, CDCl3) δ 185.1, 168.3, 135.5, 135.1, 129.9, 127.6, 124.7, 121.8, 119.1, 117.8, 23.8; ESI-MS obsd 265.9806, calcd 265.9811 [(M + H)+, M = C11H8BrNO2].
1-Acetyl-6-bromo-1H-indole-3-carbaldehyde (22-Br6). A sample of DMAP (38 mg, 0.31 mmol) was added to a mixture of 6-bromo-3-formylindole (21-Br6, 7.0 g, 31 mmol), acetic anhydride (5.9 mL, 62 mmol), and triethylamine (8.5 mL, 61 mmol) in CH2Cl2 (78 mL) at room temperature. The reaction mixture was stirred for 18 h and then concentrated. The resulting crude product was washed with ice-cold CH2Cl2 (30 mL) to afford a white solid (7.5 g, 90%): mp darkening at 214 °C, decomposed at 247 °C; 1H NMR (700 MHz, CDCl3) δ 10.11 (s, 1H), 8.65 (d, J = 1.7 Hz, 1H), 8.15 (d, J = 8.4 Hz, 1H), 8.04 (s, 1H), 7.54 (dd, J = 8.4, 1.8 Hz, 1H), 2.74 (s, 3H); 13C{1H} NMR (175 MHz, CDCl3) δ 185.2, 168.3, 136.9, 135.0, 128.8, 124.9, 123.0, 122.4, 120.7, 119.6, 23.8; ESI-MS obsd 265.9810, calcd 265.9811 [(M + H)+, M = C11H8BrNO2].
1-Acetyl-7-bromo-1H-indole-3-carbaldehyde (22-Br7). A sample of DMAP (16 mg, 0.13 mmol) was added to a mixture of 7-bromo-3-formylindole (21-Br7, 3.0 g, 13 mmol), acetic anhydride (1.3 mL, 14 mmol), and triethylamine (2.0 mL, 14 mmol) in CH2Cl2 (67 mL) at room temperature. The mixture was stirred for 4 h and then neutralized by the addition of saturated aqueous NaHCO3 (100 mL), followed by brine (100 mL). The organic layer was dried (Na2SO4) and filtered. The filtrate was concentrated and chromatographed [silica, ethyl acetate gradient 0–7% in CH2Cl2] to afford a white solid (2.1 g, 59%): mp 122–124 °C; 1H NMR (700 MHz, CDCl3) δ 10.10 (s, 1H), 8.30 (d, J = 7.8 Hz, 1H), 8.08 (s, 1H), 7.65 (d, J = 7.8 Hz, 1H), 7.29 (t, J = 7.8 Hz, 1H), 2.78 (s, 3H); 13C{1H} NMR (175 MHz, CDCl3) δ 185.0, 167.2, 137.0, 135.0, 131.8, 129.8, 126.6, 121.5, 121.3, 108.2, 25.3; ESI-MS obsd 265.9809, calcd 265.9811 [(M + H)+, M = C11H8BrNO2].
1-Acetyl-5-bromoindolin-3-one (
23-Br5). Following a reported procedure [
25] with modification, a sample of
mCPBA (purified, 863 mg, 5.0 mmol) was added to a mixture of
22-Br5 (1.06 g, 4.0 mmol) in CH
2Cl
2 (19 mL) at 0 °C under argon. The reaction mixture was stirred at 0 °C for 30 min and then at room temperature for 20.5 h. Methanol (19 mL) and acetic acid (2 mL) were then added to the reaction mixture, followed by anhydrous sodium acetate (492 mg, 6.0 mmol). The mixture was stirred at room temperature for 2 h. The reaction mixture was then concentrated. The resulting residue was dissolved in CH
2Cl
2 (100 mL), neutralized by the addition of saturated aqueous NaHCO
3 (300 mL), and washed with brine (150 mL). The organic layer was dried (Na
2SO
4) and filtered. The filtrate was concentrated and chromatographed [silica, ethyl acetate gradient 0–2% in CH
2Cl
2] to afford a white solid (695 mg, 68%): mp darkening at 111 °C, decomposed at 179 °C;
1H NMR (700 MHz, CDCl
3)
δ 8.48 (d,
J = 8.9 Hz, 1H), 7.86 (d,
J = 2.2 Hz, 1H), 7.74 (dd,
J = 8.8, 2.2 Hz, 1H), 4.32 (s, 2H), 2.32 (s, 3H);
13C{
1H} NMR (175 MHz, CDCl
3)
δ 193.1, 168.0, 152.5, 139.9, 126.5, 126.4, 120.2, 117.4, 56.3, 24.2; ESI-MS obsd 251.9672, calcd 251.9666 [(M − H)
−, M = C
10H
8BrNO
2].
1-Acetyl-6-bromoindolin-3-one (
23-Br6). Following a reported procedure [
25] with modification, a sample of
mCPBA (purified, 630 mg, 3.7 mmol) was added to a mixture of
22-Br6 (750 mg, 2.8 mmol) in CH
2Cl
2 (60 mL) at 0 °C under argon. The reaction mixture was stirred at 0 °C for 30 min and then at room temperature for 20 h. The reaction mixture was then concentrated. The resulting residue was dissolved in acetic acid/CH
2Cl
2/methanol (80 mL, 1:9.5:9.5,
v/
v/
v), followed by the addition of anhydrous sodium acetate (346 mg, 4.2 mmol). The mixture was stirred at room temperature for 3 h. The mixture was concentrated. The resulting residue was dissolved in CH
2Cl
2 (100 mL), neutralized by the addition of saturated aqueous NaHCO
3 (300 mL), and washed with brine (150 mL). The organic layer was dried (Na
2SO
4) and filtered. The filtrate was concentrated and chromatographed [silica, ethyl acetate gradient 0–1% in CH
2Cl
2] to afford a white fluffy solid (245 mg, 34%): mp darkening at 160 °C, decomposed at 182 °C;
1H NMR (700 MHz, CDCl
3)
δ 8.82 (s, 1H), 7.60 (d,
J = 8.2 Hz, 1H), 7.36 (dd,
J = 8.2, 1.6 Hz, 1H), 4.30 (s, 2H), 2.32 (s, 3H);
13C{
1H} NMR (175 MHz, CDCl
3)
δ 193.4, 168.1, 154.1, 132.8, 127.9, 124.6, 123.7, 121.9, 56.3, 24.2; ESI-MS obsd 251.9672, calcd 251.9666 [(M − H)
−, M = C
10H
8BrNO
2].
1-Acetyl-7-bromoindolin-3-one (
23-Br7). Following a reported procedure [
25] with modification, a sample of
mCPBA (75% as obtained commercially, 1.10 g, 4.8 mmol) was added to a mixture of
22-Br7 (1.06 g, 4.0 mmol) in CH
2Cl
2 (10 mL) at 0 °C under argon. The reaction mixture was stirred at 0 °C for 30 min and then at room temperature for 18 h. CH
2Cl
2 (8 mL), methanol (18 mL), and acetic acid (2 mL) were then added, followed by anhydrous sodium acetate (492 mg, 6.0 mmol). The reaction mixture was stirred at room temperature for 1 h. The mixture was concentrated. The resulting residue was dissolved in CH
2Cl
2 (100 mL), neutralized by the addition of saturated aqueous NaHCO
3 (300 mL), and washed with brine (150 mL). The organic layer was dried (Na
2SO
4) and filtered. The filtrate was concentrated and chromatographed [silica, ethyl acetate gradient 0–5% in CH
2Cl
2] to afford a white solid (459 mg, 45%): mp darkening at 96 °C, decomposed at 173 °C;
1H NMR (700 MHz, CDCl
3)
δ 8.45 (d,
J = 8.9 Hz, 1H), 7.88 (d,
J = 7.8 Hz, 1H), 7.73 (d,
J = 7.5 Hz, 1H), 7.17 (t,
J = 7.7 Hz, 1H), 4.37 (s, 2H), 2.36 (s, 3H);
13C{
1H} NMR (175 MHz, CDCl
3)
δ 194.8, 167.9, 153.4, 141.7, 129.9, 126.4, 122.8, 113.8, 57.6, 24.3; ESI-MS obsd 251.9669, calcd 251.9666 [(M − H)
−, M = C
10H
8BrNO
2].
1-Acetyl-5-bromo-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester (24-Br5). Mercury(II) oxide (238 mg, 1.1 mmol) and mercury(II) bromide (72 mg, 0.20 mmol) were added simultaneously to a mixture of 23-Br5 (254 mg, 1.0 mmol), 6 (1.19 g, 3.0 mmol), and powdered molecular sieves 3Å (300 mg) in CH2Cl2 (5 mL) under argon at room temperature, followed by stirring in a water bath (35 °C) for 21 h. The reaction mixture was treated with pyridine (242 μL, 3.0 mmol) and filtered through Celite. The filtrate was concentrated and chromatographed [silica, ethyl acetate gradient 0–4% in CH2Cl2] to afford a white solid (215 mg, 38%): mp 175–178 °C; 1H NMR (500 MHz, CDCl3) δ 8.29 (s, 1H), 7.64 (d, J = 2.0 Hz, 1H), 7.46 (dd, J = 8.8, 2.0 Hz, 1H), 7.21 (s, 1H), 5.42–5.28 (m, 3H), 5.07 (d, J = 6.7 Hz, 1H), 4.19 (d, J = 9.2 Hz, 1H), 3.77 (s, 3H), 2.58 (s, 3H), 2.14 (s, 3H), 2.07 (s, 3H), 2.06 (s, 3H); 13C{1H} NMR (175 MHz, CDCl3) δ 170.1, 169.3, 169.2, 168.2, 166.7, 139.9, 132.2, 129.2, 125.6, 120.6, 118.2, 117.1, 111.7, 100.8, 72.7, 71.7, 70.8, 68.9, 53.1, 23.8, 20.7, 20.6, 20.5; ESI-MS obsd 592.0417, calcd 592.0425 [(M + Na)+, M = C23H24BrNO11].
1-Acetyl-6-bromo-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester (24-Br6). Mercury(II) oxide (206 mg, 0.95 mmol) and mercury(II) bromide (62 mg, 0.17 mmol) were added simultaneously to a mixture of 23-Br6 (220 mg, 866 μmol), 6 (1.03 g, 2.6 mmol), and powdered molecular sieves 3Å (250 mg) in CH2Cl2 (4.3 mL) under argon at room temperature, followed by stirring in a water bath (35 °C) for 21 h. The reaction mixture was treated with pyridine (209 μL, 2.6 mmol) and filtered through Celite. The filtrate was concentrated and chromatographed [silica, ethyl acetate gradient 0–1% in CH2Cl2] to afford a white solid (218 mg, 44%): mp 196–199 °C; 1H NMR (700 MHz, CDCl3) δ 8.63 (s, 1H), 7.41 (dd, J = 8.2, 1.7 Hz, 1H), 7.36 (d, J = 8.3 Hz, 1H), 7.16 (s, 1H), 5.40–5.31 (m, 3H), 5.09 (d, J = 6.8 Hz, 1H), 4.21 (d, J = 9.0 Hz, 1H), 3.75 (s, 3H), 2.58 (s, 3H), 2.11 (s, 3H), 2.07 (s, 3H), 2.06 (s, 3H); 13C{1H} NMR (175 MHz, CDCl3) δ 170.0, 169.3, 169.1, 168.2, 166.7, 140.8, 134.0, 127.1, 122.7, 120.2, 119.8, 118.8, 110.1, 100.7, 72.7, 71.6, 70.9, 68.9, 53.1, 23.8, 20.7, 20.6, 20.5; ESI-MS obsd 592.0415, calcd 592.0425 [(M + Na)+, M = C23H24BrNO11].
1-Acetyl-7-bromo-1H-indol-3-yl 2,3,4-tri-O-acetyl-β-D-glucopyranosiduronic acid methyl ester (24-Br7). Mercury(II) bromide (49 mg, 0.14 mmol) was added to a mixture of 23-Br7 (171 mg, 0.67 mmol), 6 (802 mg, 2.0 mmol), mercury(II) oxide (160 mg, 0.74 mmol), and powdered molecular sieves 3Å (150 mg) in CH2Cl2 (3 mL) with stirring under argon at room temperature, followed by stirring in a water bath (35 °C) for 18 h. The reaction mixture was treated with pyridine (162 μL, 2.0 mmol) and filtered through Celite. The filtrate was concentrated and chromatographed [silica, ethyl acetate gradient 0–6% in CH2Cl2] to afford a white solid (128 mg, 33%): mp 103–110 °C; 1H NMR (700 MHz, CDCl3) δ 7.59 (d, J = 7.7 Hz, 1H), 7.47 (d, J = 7.8 Hz, 1H), 7.22 (s, 1H), 7.16 (t, J = 7.7 Hz, 1H), 5.41–5.31 (m, 3H), 5.07 (d, J = 6.7 Hz, 1H), 4.20 (d, J = 9.2 Hz, 1H), 3.76 (s, 3H), 2.62 (s, 3H), 2.11 (s, 3H), 2.07 (s, 3H), 2.06 (s, 3H); 13C{1H} NMR (175 MHz, CDCl3) δ 170.1, 169.3, 169.1, 166.8, 166.7, 139.8, 132.8, 131.5, 128.0, 124.9, 117.0, 112.4, 109.5, 100.8, 72.7, 71.7, 70.9, 68.9, 53.1, 24.8, 20.7, 20.6, 20.5; ESI-MS obsd 592.0418, calcd 592.0425 [(M + Na)+, M = C23H24BrNO11].
5-(2,5,8,11-Tetraoxatetradec-13-yn-14-yl)-1H-indol-3-yl β-D-glucopyranosiduronic acid (25). A mixture of 24-Br5 (120 mg, 0.21 mmol), propargyl-PEG3-OMe (P4, 128 mg, 0.63 mmol), and triethylamine/THF (1:5, 1 mL) was degassed via two cycles of freeze-pump-thaw under argon. The degassed reaction mixture was treated simultaneously with Pd(PPh3)4 (24 mg, 21 μmol) and CuI (8.0 mg, 42 μmol) at room temperature under argon and then stirred at 60 °C for 21 h. The reaction mixture was concentrated. The resulting residue was dissolved in CH2Cl2 (2 mL) and filtered through Celite. The filtrate was concentrated and chromatographed [silica, CH2Cl2/ethyl acetate (9:1 to 1:1)] to afford a crude mixture (21 mg). The crude mixture was added to a mixture of K2CO3 (6.3 mg, 46 μmol) and methanol (1.5 mL) and stirred at room temperature for 4 h, followed by filtration through Celite. The filtrate was concentrated and chromatographed on C18-reversed phase silica (4 g, column volume = 8 mL, flow rate = 15 mL/min) with the following eluants: H2O with a gradient of 0–8% acetonitrile over a period of 21 min, hold at 8% acetonitrile until 37 min, then increase abruptly to 12% acetonitrile, and hold until ≥41 min. The title compound eluted at 27.1 min, whereas the byproduct 25-elim eluted at 41.0 min. Data for the title compound: a pale yellow oil (8.2 mg, 8%); 1H NMR (700 MHz, CD3OD) δ 7.85 (s, 1H), 7.23 (d, J = 8.4 Hz, 1H), 7.22 (s, 1H), 7.14 (d, J = 8.4 Hz, 1H), 4.69 (d, J = 7.7 Hz, 1H), 4.43 (s, 2H), 3.79–3.76 (m, 2H), 3.71–3.68 (m, 2H), 3.66–3.60 (m, 7H), 3.56–3.47 (m, 5H), 3.34 (s, 3H); 13C{1H} NMR (175 MHz, CD3OD) δ 176.6, 138.9, 134.8, 126.2, 123.0, 121.3, 114.2, 113.5, 112.5, 105.8, 89.4, 82.8, 77.9, 76.6, 74.9, 73.7, 72.8, 71.33, 71.30, 71.27, 71.2, 69.9, 60.0, 59.1; ESI-MS obsd 508.1832, calcd 508.1824 [(M − H)−, M = C24H31NO11]. Data for 25-elim: ESI-MS obsd 490.1717, calcd 490.1719 [(M − H)−, M = C24H29NO10].
6-(2,5,8,11-Tetraoxatetradec-13-yn-14-yl)-1H-indol-3-yl β-D-glucopyranosiduronic acid (26). A mixture of 24-Br6 (120 mg, 0.21 mmol), propargyl-PEG3-OMe (P4, 128 mg, 0.63 mmol), and triethylamine/THF (1:5, 1 mL) was degassed via three cycles of freeze-pump-thaw under argon. The degassed reaction mixture was treated simultaneously with Pd(PPh3)4 (24 mg, 21 μmol) and CuI (8.0 mg, 42 μmol) at room temperature under argon and then stirred at 60 °C for 21 h. The reaction mixture was concentrated. The resulting residue was dissolved in CH2Cl2 (2 mL) and filtered through Celite. The filtrate was concentrated and chromatographed [silica, CH2Cl2/ethyl acetate (9:1 to 1:1)] to afford a crude mixture (41 mg). The crude mixture was added to a mixture of K2CO3 (12.3 mg, 89 μmol) and methanol (3 mL) and stirred at room temperature for 4 h, followed by filtration through Celite. The filtrate was then concentrated and chromatographed on C18-reversed phase silica (4 g, column volume = 8 mL, flow rate = 15 mL/min) with the following eluants: H2O with a gradient of 0–7% in acetonitrile over a period of 8 min, then hold at 7% acetonitrile until ≥ 12 min. The title compound eluted at 10.0 min, whereas the byproduct 26-elim eluted at 11.5 min. Data for the title compound: a pale yellow oil (25 mg, 23%); 1H NMR (700 MHz, CD3OD) δ 7.66 (d, J = 8.2 Hz, 1H), 7.38 (s, 1H), 7.24 (s, 1H), 7.03 (d, J = 8.2 Hz, 1H), 4.70 (d, J = 7.6 Hz, 1H), 4.43 (s, 2H), 3.78–3.74 (m, 2H), 3.72–3.66 (m, 3H), 3.66–3.60 (m, 6H), 3.59–3.47 (m, 5H), 3.33 (s, 3H); 13C{1H} NMR (175 MHz, CD3OD) δ 176.6, 139.1, 134.5, 123.1, 121.6, 118.8, 116.5, 116.1, 115.0, 105.8, 89.2, 83.8, 77.9, 76.6, 74.9, 73.7, 72.8, 71.37, 71.35, 71.3, 71.2, 70.0, 59.9, 59.1; ESI-MS obsd 508.1832, calcd 508.1824 [(M − H)−, M = C24H31NO11].
7-(2,5,8,11-Tetraoxatetradec-13-yn-14-yl)-1H-indol-3-yl β-D-glucopyranosiduronic acid (27). A mixture of 24-Br7 (120 mg, 0.21 mmol), propargyl-PEG3-OMe (P4, 128 mg, 0.63 mmol), and triethylamine/THF (1:5, 1 mL) was degassed via three cycles of freeze-pump-thaw under argon. The degassed reaction mixture was treated simultaneously with Pd(PPh3)4 (24 mg, 21 μmol) and CuI (8.0 mg, 42 μmol) at room temperature under argon and then stirred at 60 °C for 21 h. The reaction mixture was concentrated. The resulting residue was dissolved in CH2Cl2 (2 mL) and filtered through Celite. The filtrate was concentrated and chromatographed [silica, CH2Cl2/ethyl acetate (9:1 to 1:1)] to afford a crude mixture (65 mg). The crude mixture was added to a mixture of K2CO3 (20 mg, 0.14 mmol) and methanol (4.7 mL) and stirred at room temperature for 4 h, followed by filtration through Celite. The filtrate was concentrated and chromatographed on C18-reversed phase silica (4 g, column volume = 8 mL, flow rate = 15 mL/min) with the following eluants: H2O with a gradient of 0–10% acetonitrile over a period of 18 min, hold at 10% acetonitrile until 24.2 min, then increase to 13% acetonitrile over a period of 4 min, then hold at 13% acetonitrile until ≥31 min. The title compound eluted at 20.1 min, whereas the byproduct 27-elim eluted at 31 min. Data for the title compound: a pale yellow oil (32 mg, 30%), 1H NMR (700 MHz, CD3OD) δ 7.75 (d, J = 8.0 Hz, 1H), 7.23 (s, 1H), 7.19 (d, J = 7.2 Hz, 1H), 6.96 (t, J = 7.6 Hz, 1H), 4.70 (d, J = 7.7 Hz, 1H), 4.53 (s, 2H), 3.83–3.79 (m, 2H), 3.73–3.69 (m, 2H), 3.67–3.64 (m, 3H), 3.64–3.61 (m, 2H), 3.61–3.58 (m, 2H), 3.57–3.52 (m, 2H), 3.51–3.46 (m, 3H), 3.32 (s, 3H); 13C{1H} NMR (175 MHz, CD3OD) δ 176.6, 139.4, 135.4, 126.6, 121.6, 120.1, 119.4, 113.5, 106.7, 105.8, 89.8, 83.7, 77.9, 76.7, 74.9, 73.7, 72.8, 71.4, 71.3, 71.2, 70.2, 60.0, 59.1 (one expected carbon is missing); ESI-MS obsd 508.1829, calcd 508.1824 [(M − H)−, M = C24H31NO11].