4.2 Semi-synthesis and preparation of compounds
Compounds 1–2: To a solution of Xn (130 mg, 0.37 mM) in N, N-dimethylformamide (DMF, 4 mL) was added sodium carbonate solution (10%, 1.5 mL) and CH3I (35 µL, 0.56 mM) at 60℃ and stirred for 10 h. The reaction was quenched by addition of double distilled water (DDW), and adjusted with dilute hydrochloric acid pH to acidity, and extracted with ethyl acetate (EtOAc) three times. The combined organic extracts were concentrated under reduced pressure, dried over anhydrous Na2SO4, which was purified by chromatography on silica gel (petroleum ether/EtOAc = 30/1 to 10/1) to afford the compounds 1–2.
(E)-1-(2,4-dihydroxy-6-methoxy-3-(3-methylbut-2-en-1-yl)phenyl)-3-(4-methoxyphenyl)prop-2-en-1-one (1): 37.5 mg, yield: 27.8%, yellow powder, 1H-NMR (DMSO-d6, 300 MHz) δ 14.57 (1H, s, 2-OH), 10.60 (1H, s, 4-OH), 7.84 (1H, d, J = 15.6 Hz, H-β), 7.72 (1H, d, J = 15.6 Hz, H-α), 7.70 (2H, d, J = 8.7 Hz, H-2', H-6'), 7.03 (2H, d, J = 8.6 Hz, H-3', H-5'), 6.09 (1H, s, H-5), 5.14 (1H, m, H-2''), 3.87 (3H, s, H-7), 3.81 (3H, s, H-7'), 3.15 (2H, J = 6.8 Hz, H-1''), 1.70 (3H, s, H-5''), 1.61 (3H, s, H-4''); 13C NMR (DMSO-d6, 75 MHz) δ 191.7 (C = O), 164.6 (C-4), 162.5 (C-6), 161.1 (C-2), 160.5 (C-4'), 141.9 (C-β), 130.3 (C-2', C-6'), 129.9 (C-3''), 127.6 (C-α), 124.9 (C-1'), 123.0 (C-2''), 114.6 (C-3', C-5'), 107.3 (C-3), 104.6 (C-1), 91.0 (C-5), 55.8 (C-7), 55.4 (C-7'), 25.5 (C-5''), 21.0 (C-1''), 17.7 (C-4''); HR-ESI-MS: calcd. for C22H25O5+ [M + H]+ 369.1697, found 369.1697.
(E)-1-(2-hydroxy-4,6-dimethoxy-3-(3-methylbut-2-en-1-yl)phenyl)-3-(4-methoxyphenyl)prop-2-en-1-one (2): 17.9 mg, yield: 12.8%, yellow powder, 1H-NMR (DMSO-d6, 500 MHz) δ 14.12 (1H, s, 2-OH), 7.81 (1H, d, J = 15.6 Hz, H-β), 7.73 (1H, d, J = 15.2 Hz, H-α), 7.71 (2H, d, J = 8.8 Hz, H-2', H-6'), 7.03 (2H, d, J = 8.8 Hz, H-3', H-5'), 6.27 (1H, s, H-5), 5.10 (1H, m, H-2''), 3.98 (3H, s, H-7), 3.91 (3H, s, H-8), 3.82 (3H, s, H-7'), 3.17 (2H, d, J = 5.7 Hz, H-1''), 1.70 (3H, s, H-5''), 1.60 (3H, s, H-4''); 13C NMR (DMSO-d6, 125 MHz) δ 192.4 (C = O), 163.3 (C-4), 162.8 (C-6), 161.3 (C-2), 161.2 (C-4'), 142.3 (C-β), 130.4 (C-3''), 130.3 (C-2', C-6'), 127.5 (C-α), 124.8 (C-1'), 122.7 (C-2''), 114.6 (C-3', C-5'), 108.4 (C-3), 105.6 (C-1), 87.7 (C-2''), 56.2 (C-8), 55.9 (C-7), 55.4 (C-7'), 25.5 (C-5''), 21.0 (C-1''), 17.6 (C-4''); HR-ESI-MS: calcd. for C23H27O5+ [M + H]+ 383.1853, found 383.1854.
Compound 3: To a solution of Xn (80 mg, 0.23 mM) in absolute ethyl alcohol was added 30 mg NaOH at 65℃ and stirred for 12 h. The reaction was quenched by addition of DDW, and adjusted with dilute hydrochloric acid pH to neutral, and extracted with EtOAc three times. The combined organic extracts were concentrated under reduced pressure, dried over anhydrous Na2SO4, which was purified by chromatography on silica gel (petroleum ether/EtOAc = 1/1 to 1/2) to afford the compound 3.
7-hydroxy-2-(4-hydroxyphenyl)-5-methoxy-8-(3-methylbut-2-en-1-yl)chroman-4-one (3): 16.7 mg, yield: 19.4%, white powder, 1H-NMR (DMSO-d6, 300 MHz) δ 10.42 (1H, s, 4-OH), 9.53 (1H, s, 4'-OH), 7.30 (2H, d, J = 8.5 Hz, H-2', H-6'), 6.79 (2H, d, J = 8.5 Hz, H-3', H-5'), 6.14 (1H, s, H-5), 5.34 (1H, dd, J = 3.0 Hz, J = 12.4 Hz, H-β), 5.10 (1H, m, H-2''), 3.70 (3H, s, H-7), 3.13 (2H, J = 6.9 Hz, H-1''), 2.94 (2H, m, H-α), 1.59 (3H, s, H-5''), 1.54 (3H, s, H-4''); 13C NMR (DMSO-d6, 75 MHz) δ 188.3 (C = O), 161.6 (C-4), 161.4 (C-6), 159.6 (C-2), 157.4 (C-4'), 130.3 (C-3''), 129.6 (C-1'), 127.8 (C-2', C-6'), 122.9 (C-2''), 115.1 (C-3', C-5'), 107.5 (C-3), 104.6 (C-1), 92.7 (C-5), 77.9 (C-β), 55.4 (C-7), 44.7 (C-α), 25.5 (C-5''), 21.5 (C-1''), 17.6 (C-4''); HR-ESI-MS: calcd. for C21H23O5+ [M + H]+ 354.1467, found 355.1539.
Compounds 4–5: To a solution of Xn (300 mg, 0.85 mM) in acetonitrile (5 mL) was added morpholine (1.70 mM) at 100℃ and stirred for 3 h. The combined organic extracts were concentrated under reduced pressure, dried over anhydrous Na2SO4, which was purified by chromatography on silica gel (petroleum ether/EtOAc = 20/1 to 3/1) to afford the compounds 4–5.
(E)-1-(3-((4-bromophenyl)(morpholino)methyl)-4,6-dihydroxy-2-methoxy-5-(3-methylbut-2-en-1-yl)phenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one (4): 19.1 mg, yield: 3.7%, yellow powder, 1H-NMR (DMSO-d6, 300 MHz) δ 14.30 (1H, s, 2-OH), 13.69 (1H, s, 4'-OH), 10.17 (1H, s, 4-OH), 7.78 (1H, d, J = 15.5 Hz, H-β), 7.60 (2H, d, J = 8.4 Hz, H-2', H-6'), 7.58 (3H, d, J = 15.2 Hz, J = 7.3 Hz, H-α, H-4''', H-6'''), 7.44 (2H, d, J = 8.2 Hz, H-3''', H-7'''), 6.85 (2H, d, J = 8.3 Hz, H-3', H-5'), 5.21 (1H, m, H-2''), 4.99 (1H, s, H-1'''), 3.66 (4H, t, J = 7.1 Hz, H-9''', H-10'''), 3.42 (3H, s, H-7), 3.25 (2H, d, J = 4.7 Hz, H-1''), 2.40 (4H, t, J = 8.5 Hz, H-8''', H-11'''), 1.73 (3H, s, H-5''), 1.63 (3H, s, H-4''); 13C NMR (DMSO-d6, 75 MHz) δ 191.8 (C = O), 162.5 (C-4), 162.2 (C-6), 160.3 (C-4'), 158.8 (C-2), 144.2 (C-β), 138.4 (C-2'''), 131.9 (C-3'', C-4''', C-6'''), 130.7 (C-2', C-6'), 125.7 (C-3''', C-7'''), 122.5 (C-1', C-α), 122.0 (C-2''), 121.4 (C-5'''), 116.1 (C-3', C-5'), 112.0 (C-3), 110.6 (C-1), 107.5 (C-5), 67.7 (C-1'''), 65.8 (C-7), 63.2 (C-9''', C-10'''), 48.6 (C-8''', C-11'''), 25.5 (C-5''), 24.1 (C-1''), 17.8 (C-4''); HR-ESI-MS: calcd. for C32H35BrNO5+ [M + H]+ 608.1647, found 608.1642.
(E)-1-(2,4-dihydroxy-6-methoxy-3-(3-methylbut-2-en-1-yl)-5-(morpholino(3,4,5-trimethoxyphenyl)methyl)phenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one (5): 25.2 mg, yield: 4.8%, yellow powder, 1H-NMR (DMSO-d6, 300 MHz) δ 14.38 (1H, s, 2-OH), 13.74 (1H, s, 4'-OH), 10.16 (1H, s, 4-OH), 7.79 (1H, d, J = 15.6 Hz, H-β), 7.63 (1H, d, J = 15.8 Hz, H-α), 7.57 (2H, d, J = 8.6 Hz, H-2', H-6'), 6.86 (2H, d, J = 8.1 Hz, H-3', H-5'), 6.83 (2H, d, J = 8.1 Hz, H-3''', H-7'''), 5.26 (1H, m, H-2''), 4.98 (1H, s, H-1'''), 3.97 (3H, s, H-7), 3.73 (9H, s, H-12''', H-13''', H-14'''), 3.62 (4H, t, J = 9.1 Hz, H-9''', H-10'''), 3.26 (2H, d, J = 5.7 Hz, H-1''), 2.42 (4H, t, J = 8.6 Hz, H-8''', H-11'''), 1.74 (3H, s, H-5''), 1.60 (3H, s, H-4''); 13C NMR (DMSO-d6, 75 MHz) δ 191.7 (C = O), 162.2 (C-4), 160.3 (C-6), 158.7 (C-4'), 152.8 (C-2), 144.0 (C-4''', C-6'''), 137.1 (C-β), 130.6 (C-2', C-6', C-3''), 130.5 (C-2''', C-5'''), 125.7 (C-1'), 122.4 (C-α), 122.0 (C-2''), 116.1 (C-3', C-5'), 112.0 (C-3''', C-7'''), 111.1 (C-1, C-3), 107.4 (C-5), 68.5 (C-1'''), 65.8 (C-7, C-13'''), 63.3 (C-9''', C-10'''), 60.0 (C-12''', C-14'''), 55.6 (C-8''', C-11'''), 31.5 (C-5''), 25.5 (C-1''), 17.7 (C-4''); HR-ESI-MS: calcd. for C35H41NO9Na+ [M + Na]+ 642.2674, found 642.2674.
Compounds 6–7: To a solution of Xn (240 mg, 0.68 mM) in trichloromethane (8 mL) was added NaOH (25%, 4 mL) at 30℃ and stirred for 9 h. The reaction was quenched by addition of double distilled water (DDW), and adjusted with dilute hydrochloric acid pH to acidity, and extracted with ethyl acetate (EtOAc) three times. The combined organic extracts were concentrated under reduced pressure, dried over anhydrous Na2SO4, which was purified by chromatography on silica gel (dichloromethane/methanol = 200/1 to 30/1) to afford the compounds 6–7.
(E)-5-(3-(2,4-dihydroxy-6-methoxy-3-(3-methylbut-2-en-1-yl)phenyl)-3-oxoprop-1-en-1-yl)-2-hydroxybenzaldehyde (6): 7.2 mg, yield: 2.8%, yellow powder, 1H-NMR (DMSO-d6, 300 MHz) δ 10.28 (1H, s, H-7'), 7.77 (1H, d, J = 2.3 Hz, H-6'), 7.65 (1H, dd, J = 2.4 Hz, J = 8.6 Hz, H-2'), 7.05 (1H, d, J = 8.6 Hz, H-3'), 6.15 (1H, s, H-5), 5.43 (1H, dd, J = 3.1 Hz, J = 12.5 Hz, H-β), 5.10 (1H, m, H-2''), 3.70 (3H, s, H-7), 3.39 (4H, m, H-1'', H-α), 1.58 (3H, s, H-4''), 1.52 (3H, s, H-5''); 13C NMR (DMSO-d6, 75 MHz) δ 191.0 (C = O), 187.9 (C-7'), 161.7 (C-4), 161.2 (C-6), 160.7 (C-4'), 159.7 (C-2), 134.5 (C-2'), 130.6 (C-3''), 126.8 (C-5'), 122.8 (C-6'), 122.1 (C-2''), 117.5 (C-3'), 107.6 (C-3), 104.6 (C-1), 92.8 (C-5), 77.3 (C-β), 55.4 (C-7), 44.6 (C-α), 25.5 (C-5''), 21.6 (C-1''), 17.6 (C-4''); HR-ESI-MS: calcd. for C22H23O6+ [M + H]+ 383.1416, found 383.1490.
(E)-2,4-dihydroxy-5-(3-(4-hydroxyphenyl)acryloyl)-6-methoxy-3-(3-methylbut-2-en-1-yl)benzaldehyde (7): 21.5 mg, yield: 8.3%, yellow powder, 1H-NMR (DMSO-d6, 300 MHz) δ 10.23 (1H, s, 4'-OH), 10.06 (1H, d, J = 1.1 Hz, H-8), 7.83 (1H, d, J = 15.6 Hz, H-β), 7.64 (2H, d, J = 8.3 Hz, H-2', H-6'), 7.59 (1H, d, H-α), 6.87 (2H, d, J = 8.4 Hz, H-3', H-5'), 5.40 (1H, m, H-2''), 3.87 (3H, s, H-7), 3.20 (2H, d, J = 7.2 Hz, H-1''), 1.71 (3H, s, H-4''), 1.62 (3H, s, H-5''); 13C NMR (DMSO-d6, 75 MHz) δ 193.5 (C = O), 192.4 (C-8), 167.2 (C-4), 166.1 (C-2), 164.2 (C-6), 160.7 (C-4'), 145.8 (C-β), 131.4 (C-3''), 131.1 (C-2', C-6'), 125.4 (C-1'), 122.0 (C-α), 121.3 (C-2''), 116.1 (C-3', C-5'), 109.2 (C-5), 108.3 (C-1), 66.0 (C-7), 25.4 (C-5''), 20.5 (C-1''), 17.7 (C-4''); HR-ESI-MS: calcd. for C22H23O6+ [M + H]+ 383.1416, found 383.1489.
Compound 8: To a solution of compound 7 (20 mg, 0.05 mM) and Aminoguanidine bicarbonate (15 mg, 0.11 mM) in 3 mL absolute ethyl alcohol was added 500 µL aceticacid at 50℃ and stirred for 5 h. The combined organic extracts were concentrated under reduced pressure, dried over anhydrous Na2SO4, which was purified by chromatography on silica gel (dichloromethane/methanol = 50/1 to 20/1) to afford the compound 8.
2-((E)-2,4-dihydroxy-5-((E)-3-(4-hydroxyphenyl)acryloyl)-6-methoxy-3-(3-methylbut-2-en-1-yl)benzylidene)hydrazine-1-carboximidamide (8): 5.1 mg, yield: 22.85%, yellow powder, 1H-NMR (DMSO-d6, 300 MHz) δ 13.68 (1H, s, 2-OH), 12.03 (1H, s, -NH), 10.57 (1H, s, 4-OH), 10.27 (1H, s, 4'-OH), 8.54 (1H, s, H-8), 7.90 (3H, s, -NH2, =NH), 7.84 (1H, d, J = 15.5 Hz, H-β), 7.64 (1H, d, J = 14.2 Hz, H-α), 7.64 (2H, d, J = 9.2 Hz, H-2', H-6'), 6.88 (2H, d, J = 8.3 Hz, H-3', H-5'), 5.17 (1H, m, H-2''), 3.74 (3H, s, H-7), 3.29 (2H, d, J = 6.5 Hz, H-1''), 1.74 (3H, s, H-4''), 1.63 (3H, s, H-5''); 13C NMR (DMSO-d6, 75 MHz) δ 192.4 (C = O), 163.8 (C-4), 161.4 (C-2), 160.6 (C-6), 160.2 (C = NH), 154.4 (C-4'), 146.6 (C-β), 145.3 (C-8), 131.2 (C-3''), 131.0 (C-2', C-6'), 125.6 (C-1'), 122.1 (C-α), 121.9 (C-2''), 116.1 (C-3', C-5'), 112.0 (C-3), 109.0 (C-5), 104.6 (C-1), 64.8 (C-7), 25.5 (C-5''), 20.8 (C-1''), 17.8 (C-4''); HR-ESI-MS: calcd. for C23H26N4O5+ [M + H]+ 439.1903, found 439.1979.