Synthesis and biological evaluation of (+)-paeoveitol derivatives as novel antidepressants

Chemistry

(+) and (−)-paeoveitol were synthesized according to our previously reported method [12], and other chemical reagents and reaction solvents were purchased from J&K Scientific or Energy Chemical. 1H NMR and 13C NMR spectra were recorded on Avance III HD 400 (Bruker, Germany), Avance III 500 (Bruker, Germany) with TMS as the internal standard. High resolution mass spectra (HRMS) data were obtained from a Shimadzu LC/MS-IT-TOF mass spectrometer (Shimadzu, Kyoto, Japan). Optical rotations were measured on an Autopol VI (Serial #91058) manufactured by Rudolph Research Analytical. All synthetic compounds were purified by column chromatography on silica gel (200–300 mesh) that was purchased from Qingdao Makall Group Co., Ltd.

(5aS,10aR,11R) - 5a- (acetoxymethyl)- 3,8,11- trimethyl - 5a,10a - dihydro - 11H-benzofuro [3,2-b] chromene-2,7-diyl diacetate (2)

To a solution of (+)-paeoveitol (33 mg, 0.1 mmol) in 1 mL of pyridine was added acetic anhydride (1 mL), the reaction mixture was stirred at 25 °C for 10 h, quenched with 10 mL of water and extracted with ethyl acetate (3 × 10 mL). The combined organic phases were washed with 5% HCl solution, saturated NaHCO3 and NaCl solution in turn, dried with anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The residue was subjected to flash column chromatography on silica gel (acetone-petroleum ether, 10:90) to provide compound 2 (43 mg, 94% yield) as a white powder. \([\alpha]_}^\) - 17.16 (c 0.076, MeOH); 1H NMR (500 MHz, CDCl3) δ 6.97 (s, 1H, H-15), 6.80 (s, 1H, H-1), 6.58 (s, 1H, H-4), 6.49 (s, 1H, H-12), 5.02 (d, J = 3.0 Hz, 1H, H-8), 4.75 (d, J = 14.4 Hz, 1H, H-18a), 4.48 (d, J = 13.6 Hz, 1H, H-18b), 3.11-3.09 (m, 1H, H-7), 2.29 (s, 3H, -OAc), 2.27 (s, 3H, -OAc), 2.09 (s, 3H, -OAc), 2.05 (s, 3H, H-19), 2.00 (s, 3H, H-16), 1.56 (d, J = 8.4 Hz, 3H, H-17); 13C NMR (125 MHz, CDCl3) δ 170.6 (C = O), 169.6 (C = O), 169.5 (C = O), 158.0 (C-11), 151.1 (C-2), 144.5 (C-14), 143.1 (C-5), 133.8 (C-13), 129.1 (C-10), 126.5 (C-6), 123.9 (C-2), 120.1 (C-4), 119.3 (C-1), 117.7 (C-12), 112.0 (C-15), 89.2 (C-8), 86.0 (C-9), 67.1 (C-18), 32.2 (C-7), 20.8 (-OAc), 20.8 (-OAc), 20.8 (-OAc), 16.8 (C-19), 15.9 (C-16), 13.2 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C25H27O8]+ 455.1706, found 455.1789.

Synthesis of compounds 2 and 3

To a solution of (+)-paeoveitol (328 mg, 1 mmol) in 4 mL of tetrahydrofuran was added 1 M NaOH solution (1 mL, 1 mmol) and the mixture was stirred for 5 min at room temperature. Then, 1-acetyl-1H-1,2,3-triazolo[4,5-B] pyridine (162 mg, 1 mmol) was added and the reaction mixture was stirred for an additional 30 min. Upon completion, water (5 mL) was added and the mixture was neutralized with 1 M HCl solution. The mixture was extracted with EtOAc (3 × 10 mL), washed with brine, dried with anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The residue was subjected to flash column chromatography on silica gel (acetone-petroleum ether, 15:85) to provide compound 3 (181 mg, 49% yield) and compound 4 (95 mg, 23% yield).

(5aS,10aR,11R)-2-hydroxy-5a-(hydroxymethyl)-3,8,11-trimethyl-5a,10a-dihydro-11H -benzofuro [3,2-b] chromen- 7-yl acetate (3)

White powder. 1H NMR (500 MHz, CD3OD) δ 7.00 (s, 1H, H-1), 6.63 (s, 1H, H-4), 6.42 (s, 1H, H-15), 6.37 (s, 1H, H-12), 5.10 (d, J = 3.0 Hz, 1H, H-8), 4.14 (d, J = 11.5 Hz, 1H, H-18a), 3.98 (d, J = 11.5 Hz, 1H, H-18b), 3.07-3.02 (m, 1H, H-7), 2.24 (s, 3H, H-19), 2.01 (s, 3H, H-16), 1.95 (s, 3H, -OAc), 1.54 (d, J = 7.5 Hz, 3H, H-17);13C NMR (125 MHz, CD3OD) δ 171.8 (OAc), 159.8 (C-11), 151.6 (C-2), 148.0 (C-5), 144.2 (C-14), 134.2 (C-13), 128.4 (C-6), 126.6 (C-10), 123.9 (C-2), 120.9 (C-4), 118.9 (C-15), 113.2 (C-1), 112.2 (C-12), 91.0 (C-8), 89.5 (C-9), 67.1 (C-18), 33.7 (C-7), 20.7 (OAc), 16.7 (C-16), 16.0 (C-19), 13.6 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C21H23O6]+ 371.1495, found 371.1503.

(5aS,10aR,11R)-5a-(hydroxymethyl)-3,8,11-trimethyl-5a,10a-dihydro-11H-benzofuro [3,2-b] chromene-2,7-diyl diacetate (4)

White powder. \([\alpha]_}^\) – 11.0 (c 0.072, MeOH); 1H NMR (400 MHz, CDCl3) δ 6.94 (s, 1H, H-15), 6.81 (s, 1H, H-1), 6.56 (s, 1H, H-4), 6.47 (s, 1H, H-12), 5.10 (d, J = 3.2 Hz, 1H, H-8), 4.20 (d, J = 12.0 Hz, 1H, H-18a), 3.96 (d, J = 13.6 Hz, 1H, H-18a), 3.06-3.03 (m, 1H, H-7), 2.28 (s, 3H, -OAc), 2.26 (s, 3H, -OAc), 2.03 (s, 3H, H-19), 2.00 (s, 3H, H-16), 1.55 (d, J = 6.8 Hz, 3H, H-17); 13C NMR (100 MHz, CDCl3) δ 169.7 (C = O), 169.6 (C = O), 158.3 (C-11), 151.3 (C-5), 144.5 (C-2), 142.9 (C-14), 133.5 (C-13), 129.0 (C-6), 127.0 (C-10), 124.2 (C-3) 120.0 (C-4), 119.3 (C-1), 117.5 (C-15), 112.0 (C-12), 89.4 (C-8), 88.0 (C-9), 67.1 (C-18), 32.6 (C-7), 20.8 (-OAc), 20.7 (-OAc), 16.8 (C-19), 15.9 (C-16), 13.1 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C23H25O7]+ 413.1600, found 413.1604.

General synthetic procedures for compounds 5-21

To a solution of compound 4 (20.6 mg, 0.05 mmol) in CH2Cl2 (10 mL), Dess-Martin periodinane (31.8 mg, 0.075 mmol, 1.5 equiv) was added slowly. After stirring at room temperature for 2 h, the mixture was quenched with saturated Na2S2O3 (10 mL), and the aqueous layer was extracted with CH2Cl2 (3 × 10 mL). The combined organic phases were washed with saturated NaHCO3 (10 mL), and brine (10 mL), dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure to yield crude aldehyde. A mixture of aldehyde, amine (0.075 mmol) and NaBH(OAc)3(15.9 mg, 0.075 mmol) and AcOH (1 μL) in CH2Cl2 (1 mL) was stirred at room temperature for 12 h. Upon completion, 2 M NaOH solution (1 mL) was added and stirred for another 6 h. The reaction mixture was neutralized with 1 M HCl solution and extracted with CH2Cl2 (3 × 5 mL), washed with brine, dried with anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The crude product was purified by column chromatography on silica gel (Et3N-ethyl acetate-petroleum ether, 1:30:70) to afford products 5-21.

(5aS,10aR,11R)-5a-((dimethylamino)methyl)-3,8,11-trimethyl-5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (5)

White powder, 12 mg, 69% yield, \([\alpha]_}^\) + 223.53 (c 0.085, MeOH); 1H NMR (400 MHz, pyridine-d5) δ 7.43 (s, 1H, H-15), 7.11 (s, 1H, H-1), 6.81 (s, 1H, H-4), 6.61 (s, 1H, H-12), 5.36 (d, J = 2.8 Hz, 1H, H-8), 3.33-3.30 (m, 1H, H-7), 3.22 (d, J = 13.6 Hz, 1H, H-18a), 2.94 (d, J = 13.6 Hz, 1H, H-18b), 2.36 (s, 6H, N-Me), 2.25 (s, 3H, H-19), 2.19 (s, 3H, H-16), 1.61 (d, J = 7.2 Hz, 3H, H-17); 13C NMR (100 MHz, pyridine-d5) δ 153.6 (C-11), 151.7 (C-2), 150.5 (C-14), 147.0 (C-5), 127.8 (C-13), 127.7 (C-6), 126.9 (C-10), 122.9 (C-3), 120.1 (C-4), 112.8 (C-1), 111.6 (C-12), 110. 7 (C-15), 89.7 (C-8), 89.3 (C-9), 65.9 (C-18), 47.8 (N-Me), 32.9 (C-7), 16.9 (C-19), 16.1 (C-16), 13.5 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C21H26NO4]+ 356.1856, found 356.1838.

(5aS,10aR,11R)-5a-((diethylamino)methyl)-3,8,11-trimethyl-5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (6)

White powder, 14 mg, 71% yield, \([\alpha]_}^\) + 163.13 (c 0.055, MeOH);1H NMR (500 MHz, pyridine-d5) δ 7.46 (s, 1H, H-15), 7.13 (s, 1H, H-1), 6.82 (s, 1H, H-4), 6.62 (s, 1H, H-12), 5.33 (d, J = 2.5 Hz, 1H, H-8), 3.44-3.35 (m, 2H, H-7, H-18a), 3.06 (d, J = 14.0 Hz, 1H, H-18b), 2.84-2.77 (m, 2H, H-1′), 2.65-2.58 (m, 2H, H-1′), 2.25 (s, 3H, H-19), 2.19 (s, 3H, H-16), 1.65 (d, J = 7.0 Hz, 3H, H-17), 1.00-0.97 (m, 6H, H-2′); 13C NMR (125 MHz, pyridine-d5) δ 153.8 (C-11), 151.9 (C-2), 150.7 (C-14), 147.3 (C-5), 128.0 (C-13), 127.3 (C-6), 127.3 (C-10),123.1 (C-2), 120.3 (C-4), 113.0 (C-1), 111.9 (C-11), 111.0 (C-15), 90.1 (C-8), 90.0 (C-9), 60.7 (C-18), 46.6 (C-1′), 33.1 (C-2′), 17.2 (C-19), 16.3 (C-16), 13.8 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C23H30NO4]+ 384.2169, found 384.2146.

(5aS,10aR,11R)-5a-((dipropylamino)methyl)-3,8,11-trimethyl-5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (7)

White powder, 13 mg, 65% yield, \([\alpha]_}^\) + 168.63 (c 0.102, MeOH); 1H NMR (500 MHz, pyridine-d5) δ 7.45 (s, 1H, H-15), 7.14 (s, 1H, H-1), 6.83 (s, 1H, H-4), 6.62 (s, 1H, H-12), 5.33 (d, J = 3.0 Hz, 1H, H-8), 3.44-3.40 (m, 2H, H-7, H-18a), 3.06 (d, J = 13.0 Hz, 1H, H-18b), 2.73-2.65 (m, 2H, H-1′), 2.52-2.48 (m, 2H, H-1′), 2.25 (s, 3H, H-19), 2.18 (s, 3H, H-16), 1.68 (d, J = 7.0 Hz, 3H, H-17), 1.45-1.39 (m, 4H, H-2′), 0.82 (t, J = 7.0 Hz, 6H, H-3′); 13C NMR (125 MHz, pyridine-d5) δ 153.9 (C-11), 151.9 (C-2), 150.7 (C-14), 147.4 (C-5), 128.0 (C-13), 127.3 (C-6), 127.3 (C-6), 123.1 (C-3), 120.3 (C-4), 113.0 (C-1), 111.8 (C-12), 111.0 (C-15), 90.2 (C-8), 90.1 (C-9), 62.1 (C-18), 59.2 (C-1′), 33.1 (C-7), 20.7 (C-2′), 17.2 (C-19), 16.4 (C-16), 13.8 (C-17), 11.1(C-3′); HRMS (ESI, m/z): [M + H]+ calcd for [C25H34NO4]+ 412.2482, found 412.2466.

(5aS,10aR,11R)-5a-((dibutylamino)methyl)-3,8,11-trimethyl-5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (8)

White powder, 13 mg, 60% yield, \([\alpha]_}^\) + 169.43 (c 0.091, MeOH); 1H NMR (500 MHz, pyridine-d5) δ 7.47 (s, 1H, H-15), 7.14 (s, 1H, H-1), 6.84 (s, 1H, H-4), 6.62 (s, 1H, H-12), 5.36 (d, J = 3.0 Hz, 1H, H-8), 3.45-3.41 (m, 2H, H-7, H-18a), 3.11 (d, J = 14.5 Hz, 1H, H-18b), 2.78-2.73 (m, 2H, H-1′), 2.59-2.53 (m, 2H, H-1′), 2.25 (s, 3H, H-19), 2.18 (s, 3H, H-16), 1.68 (d, J = 7.0 Hz, 3H, H-17), 1.45-1.40 (m, 4H, H-2′), 1.29-1.24 (m, 4H, H-3′), 0.85 (t, J = 7.0 Hz, 6H, H-4′); 13C NMR (125 MHz, pyridine-d5) δ 153.8 (C-11), 151.9 (C-2), 150.7 (C-14), 147.4 (C-6), 128.0 (C-13), 128.0 (C-6), 127.3 (C-10), 123.1 (C-3), 120.3 (C-4), 113.0 (C-1), 111.9 (C-12), 111.0 (C-15), 90.2 (C-8), 90.1 (C-9), 62.1 (C-18), 55.9 (C-1′), 33.1 (C-7), 29.8 (C-2′), 20.8 (C-3′), 17.2 (C-19), 16.4 (C-16), 14.3 (C-4′), 13.8 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C27H28NO4]+ 440.2795, found 440.2787.

(5aS,10aR,11R)-3,8,11- trimethyl-5a-(morpholinomethyl)- 5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (9)

White powder, 15 mg, 75% yield, \([\alpha]_}^\) + 191.37 (c 0.035, MeOH); 1H NMR (500 MHz, pyridine-d5) δ 7.59 (s, 1H, H-15), 7.14 (s, 1H, H-1), 6.82 (s, 1H, H-4), 6.62 (s, 1H, H-12), 5.33 (d, J = 3.0 Hz, 1H, H-8), 3.68-3.66 (m, 4H, H-2′), 3.37-3.35 (m, 1H, H-7),3.31 (d, J = 14.0 Hz, 1H, H-18a), 2.95 (d, J = 14.0 Hz, 1H, H-18b), 2.84-2.80 (m, 2H, H-1′), 2.64-2.60 (m, 2H, H-1′), 2.25 (s, 3H, H-19), 2.20 (s, 3H, H-16), 1.67 (d, J = 8.4 Hz, H-17); 1H NMR (125 MHz, pyridine-d5) δ 153.8 (C-11), 152.1 (C-2), 150.8 (C-14), 147.1 (C-5), 128.2 (C-13), 128.0 (C-6), 127.1 (C-10), 123.3 (C-3), 120.4 (C-4), 113.1 (C-1), 112.0 (C-12), 110.9 (C-15), 90.1 (C-8), 89.7 (C-9), 67.3 (C-2′), 65.6 (C-18), 56.1 (C-1′), 33.3 (C-3), 17.2 (C-19), 16.4 (C-16), 13.8 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C23H28NO5]+ 398.1962, found 398.1938.

(5aS,10aR,11R)-3,8,11-trimethyl-5a-(pyrrolidin-1-ylmethyl)-5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (10)

White powder, 13 mg, 71% yield, \([\alpha]_}^\) + 196.59 (c 0.051, MeOH); 1H NMR (500 MHz, pyridine-d5) δ 7.44 (s, 1H, H-15), 7.11 (s, 1H, H-1), 6.83 (s, 1H, H-4), 6.61 (s, 1H, H-12), 5.38 (d, J = 3.0 Hz, 1H, H-8), 3.39 (d, J = 13.5 Hz, 1H, H-18a), 3.31-3.26 (m, 1H, H-7), 3.18 (d, J = 13.5 Hz, 1H, H-18b), 2.73-2.62 (m, 4H, H-1′), 2.25 (s, 3H, H-19), 2.20 (s, 3H, H-16), 1.62-1.58 (m, 7H, H-1′, H-17); 1H NMR (125 MHz, pyridine-d5) δ 153.9 (C-11), 151.9 (C-2), 150.7 (C-14), 147.3 (C-5), 128.1 (C-13), 127.9 (C-6), 127.2 (C-10), 123.2 (C-3), 120.4 (C-4), 113.1 (C-1), 111.9 (C-12), 111.0 (C-15), 90.0 (C-8), 89.2 (C-9), 63.2 (C-18), 56.8 (C-1′), 33.1 (C-7), 23.3 (C-2′), 17.2 (C-19), 16.4 (C-17), 13.8 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C23H28NO4]+ 382.2013, found 382.2007.

(5aS,10aR,11R)-3,8,11-trimethyl-5a-((4-methyl-1,4-diazepan-1-yl)methyl)-5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (11)

White powder, 13 mg, 62% yield, \([\alpha]_}^\) + 166.09 (c 0.044, MeOH); 1H NMR (500 MHz, pyridine-d5) δ 7.44 (s, 1H, H-15), 7.14 (s, 1H, H-1), 6.83 (s, 1H, H-4), 6.62 (s, 1H, H-12), 5.38 (d, J = 3.0 Hz, 1H, H-8), 3.54 (d, J = 14.5 Hz, 1H, H-18a), 3.44-3.41 (m, 1H, H-7), 3.17 (d, J = 14.5 Hz, 1H, H-18b), 3.08-3.05 (m, 2H, H-1′), 2.97-2.93 (m, 2H, H-2′), 2.50-2.52 (m, 2H, H-3′, H-5′), 2.25 (s, 3H, H-19), 2.25 (s, 3H, H-6′), 2.19 (s, 3H, H-16), 1.75-1.71 (m, 2H, H-4′), 1.68 (d, J = 7.0 Hz, 3H, H-17); 13C NMR (125 MHz, pyridine-d5) δ 154.0 (C-11), 151.9 (C-2), 150.7 (C-14), 147.4 (C-5), 128.1 (C-13), 128.0 (C-6), 127.2 (C-10), 123.1 (C-3), 120.4 (C-4), 113.1 (C-1), 111.9 (C-12), 111.0 (C-15), 90.2 (C-9), 90.0 (C-8), 64.9 (C-18), 58.9 (C-2′), 57.6 (C-1′), 57.0 (C-3′), 56.9 (C-5′), 47.1 (C-6′), 33.2 (C-7), 28.3 (C-4′), 17.2 (C-19), 16.4 (C-16), 13.7 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C25H33N2O4]+ 425.2435, found 425.2387.

(5aS,10aR,11R)-3,8,11-trimethyl-5a-(piperazin-1-ylmethyl)-5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (12)

White powder, 10 mg, 52% yield, \([\alpha]_}^\) + 158.36 (c 0.028, MeOH); 1H NMR (500 MHz, pyridine-d5) δ 7.45 (s, 1H, H-15), 7.14 (s, 1H, H-11), 6.82 (s, 1H, H-4), 6.61 (s, 1H, H-12), 5.35 (d, J = 3.0 Hz, 1H, H-8), 3.39-3.38 (m,1H, H-7), 3.33 (d, J = 14.0 Hz, 1H, H-18a), 2.96 (d, J = 14.0 Hz, 1H, H-18b), 2.89-2.85 (m, 6H, H-2′, H-1′), 2.64-2.62 (m, 2H, H-1′), 2.24 (s, 3H, H-19), 2.19 (s, 3H, H-16), 1.66 (d, J = 7.0 Hz, 3H, H-17); 13C NMR (125 MHz, pyridine-d5) δ 153.8 (C-11), 152.0 (C-2), 150.8 (C-14), 147.2 (C-5), 128.1 (C-13), 128.0 (C-6), 127.2 (C-10), 123.2 (C-3), 120.4 (C-4), 113.1 (C-1), 111.9 (C-12), 110. 9 (C-15), 90.1 (C-8), 89.8 (C-9), 65.8 (C-18), 56.8 (C-1′), 46.6 (C-2′), 33.2 (C-7), 17.2 (C-19), 16.3 (C-16), 13.8 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C23H28N2O4]+ 397.2122, found 397.2106.

(5aS,10aR,11R)-3,8,11-trimethyl-5a-((4-methylpiperazin-1-yl)methyl)-5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (13)

White powder, 16 mg, 78% yield, \([\alpha]^}_\) + 174.58 (c 0.072, MeOH);1H NMR (400 MHz, CD3OD) δ 6.73 (s, 1H, H-15), 6.59 (s, 1H, H-1), 6.33 (s, 1H, H-4), 6.27 (s, 1H, H-12), 5.03 (d, J = 3.2 Hz, 1H, H-8), 3.14 (d, J = 14.0 Hz, 1H, H-18a), 3.07-3.04 (m, 1H, H-7), 2.87-2.84 (m, 3H, H-18b, H-1′), 2.64-2.49 (m, 6H, H-1′, H-2′), 2.28 (s, 3H, H-3′), 2.06 (s, 3H, H-19), 2.01 (s, 3H, H-16), 1.52 (d, J = 7.2 Hz, 3H, H-17); 13C NMR (100 MHz, CD3OD) δ 153.3 (C-11), 149.9 (C-2), 148.7 (C-14), 146.6 (C-5), 127.3 (C-13), 127.2 (C-6), 125.8 (C-10), 122.2 (C-3), 119.3 (C-4), 111.9 (C-1), 110.6 (C-12), 109.5 (C-15), 89.5 (C-8), 89.1 (C-9), 63.9 (C-18), 54.9 (C-1′), 54.2 (C-2′), 44.6 (C-3′), 32.5 (C-7), 15.5 (C-19), 14.6 (C-16), 12.4 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C24H30N2O4]+ 411.2278, found 411.2248.

(5aS,10aR,11R)-5a-((4-ethylpiperazin-1-yl)methyl)-3,8,11-trimethyl-5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (14)

White powder, 17 mg, 79% yield, \([\alpha]_}^\) + 185.12 (c 0.034, MeOH);1H NMR (500 MHz, pyridine-d5) δ 7.45 (s, 1H, H-15), 7.14 (s, 1H, H-1), 6.82 (s, 1H, H-4), 6.62 (s, 1H, H-12), 5.34 (d, J = 3.0 Hz, 1H, H-8), 3.41-3.38 (m, 1H, H-7), 3.34 (d, J = 13.5 Hz, 1H, H-18a), 2.99 (d, J = 13.5 Hz, 1H, H-18b), 2.91-2.89 (m, 2H, H-1′), 2.73-2.71 (m, 2H, H-1′), 2.40-2.34 (m, 4H, H-2′), 2.25 (s, 3H, H-19), 2.24 (q, 2H, J = 7.5 Hz, H-3′), 2.19 (s, 3H, H-16), 1.67 (d, J = 6.0 Hz, 3H, H-17), 0.98 (t, 3H, J = 7.5 Hz, H-3′);13C NMR (125 MHz, pyridine-d5) δ 153.8 (C-11), 152.0 (C-2), 150.8 (C-14), 147.2 (C-5), 128.1 (C-13), 128.0 (C-6), 127.2 (C-10), 123.2 (C-3), 120.4 (C-4), 113.1 (C-1), 111.9 (C-12), 110.9 (C-15), 90.1 (C-8), 89.7 (C-9), 65.9 (C-18), 55.8 (C-1′), 53.5 (C-2′), 52.4 (C-3′), 33.2 (C-7), 17.2 (C-19), 16.3 (C-16), 13.8 (C-17), 12.4 (C-4′); HRMS (ESI, m/z): [M + H]+ calcd for [C25H32N2O4]+ 425.2435, found 425.2393.

(5aS,10aR,11R)-5a-((4-(2-methoxyphenyl)piperazin-1-yl)methyl)-3,8,11-trimethyl- 5a,10a-dihydro- 11H-benzofuro[3,2-b]chromene-2,7-diol (15)

White powder, 15 mg, 61% yield, \([\alpha]_}^\) + 160.77 (c 0.057, MeOH);1H NMR (500 MHz, pyridine-d5) δ 7.48 (s, 1H, H-15), 7.15 (s, 1H, H-1), 7.07-7.00 (m, 2H, H-5′, H-7′), 6.96-6.93 (m, 2H, H-6′, H-8′), 6.85 (s, 1H, H-4), 6.63 (s, 1H, H-12), 5.37 (d, J = 3.0 Hz, 1H, H-8), 3.75 (s, 3H, OMe), 3.43-3.37 (m, 2H, H-7, H-18a), 3.14-3.04 (m, 7H, H-18b, H-1′, H-2′), 2.88-2.85 (m, 2H, H-1′), 2.26 (s, 3H, H-19), 2.20 (s, 3H, H-16), 1.68 (d, J = 7.0 Hz, 3H, H-17); 13C NMR (125 MHz, pyridine-d5) δ 153.8 (C-11), 153.0 (C-3′), 152.0 (C-2), 150.8 (C-14), 147.2 (C-5), 142.3 (C-4′), 128.1 (C-13), 128.0 (C-6), 127.2 (C-10), 123.2 (C-8′), 122.9 (C-3), 121.5 (C-6′), 120.4 (C-7′), 118.6 (C-4), 113.1 (C-5′), 112.5 (C-1), 111.9 (C-12), 111.0 (C-15), 90.1 (C-9), 89.7 (C-8), 65.2 (C-18), 55.9 (C-2′), 55.5 (OMe), 51.1 (C-1′), 33.2 (C-7), 17.2 (C-19), 16.4 (C-16), 13.8 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C30H35N2O5]+ 503.2540, found 503.2506.

(5aS,10aR,11R)-3,8,11-trimethyl-5a-((4-(p-tolyl)piperazin-1-yl)methyl)-5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (16)

White powder, 14 mg, 59% yield, \([\alpha]_}^\) + 132.21 (c 0.037, MeOH); 1H NMR (500 MHz, pyridine-d5) δ 7.49 (s, 1H, H-15), 7.15-7.13 (m, 3H, H-1, H-5′), 6.93 (d, J = 9.0 Hz, H-4′), 6.85 (s, 1H, H-4), 6.63 (s, 1H, H-15), 5.33 (d, J = 3.0 Hz, 1H, H-8), 3.44-3.34 (m, 2H, H-7, H-18a), 3.11 (d, J = 5.0 Hz, 4H, H-2′), 3.10-2.96 (m, 3H, H-18b, H-1′), 2.82-2.77 (m, 2H, H-1′), 2.26 (s, 1H, H-19), 2.23 (s, 1H, H-7′), 2.20 (s, 1H, H-16), 1.67 (d, J = 7.0 Hz, H-17); 13C NMR (125 MHz, pyridine-d5) δ 153.8 (C-11), 152.0 (C-2), 150.8 (C-14), 149.9 (C-3′), 147.2 (C-5), 130.0 (C-5′) 128.5 (C-6′), 128.1 (C-13), 128.0 (C-6), 127.1 (C-10), 123.2 (C-2), 120.4 (C-4), 116.4 (C-4′), 113.1 (C-1), 112.0 (C-12), 111.0 (C-15), 90.1 (C-8), 89.7 (C-9), 65.0 (C-18), 55.5 (C-2′), 49.8 (C-1′), 33.2 (C-7), 20.4 (C-7′), 17.2 (C-19), 16.4 (C-16), 13.8 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C30H35N2O4]+ 487.2591, found 487.2561.

(5aS,10aR,11R) -5a-((4-([1,1′ - biphenyl] - 4- yl) piperazin-1-yl) methyl) - 3,8,11-trimethyl -5a, 10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (17)

White powder, 17 mg, 63% yield, \([\alpha]_}^\) + 119.77 (c 0.026, MeOH);1H NMR (500 MHz, pyridine-d5) δ 7.74-7.69 (m, 4H, H-8′, H-9′), 7.51 (s, 1H, H-15), 7.49-7.45 (m, 2H, H-5′), 7.34-7.31 (m,1H, H-10′), 7.16 (s, 1H, H-1), 7.08 (d, J = 9.0 Hz, 2H, H-4′), 6.86 (s, 1H, H-2), 6.64 (s, 1H, H-12), 5.34 (d, J = 3.0 Hz, 1H, H-8), 3.42-3.35 (m, 2H, H-7, H-18a), 3.20-3.18 (m, 4H, H-2′), 3.05-2.97 (m, 3H, H-18b, H-1′), 2.83-2.80 (m, 2H, H-1′), 2.27 (s, 3H, H-19), 2.21 (s, 3H, H-16), 1.69 (d, 3H, J = 7.0 Hz, H-17); 13C NMR (125 MHz, pyridine-d5) δ 153.8 (C-11), 152.1 (C-2), 151.3 (C-3′), 150.8 (C-14),147.2 (C-5), 141.3 (C-7′), 131.7 (C-6′), 129.3 (C-9′), 128.1 (C-13), 128.0 (C-6), 127.9 (C-5′), 127.1 (C-10), 126.8 (C-10′), 126.7 (C-8′), 123.3 (C-2), 120.4 (C-4), 116.2 (C-4′), 113.1 (C-1), 112.0 (C-12), 111.0 (C-15), 90.1 (C-8), 89.7 (C-9), 65.0 (C-18), 55.4 (C-2′), 49.0 (C-1′), 33.2 (C-7), 17.2 (C-19), 16.4 (C-16), 13.8 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C35H36N2O4]+ 549.2748, found 549.2740.

(5aS,10aR,11R)-3,8,11-trimethyl-5a-((4-(3-methylbenzyl)piperazin-1-yl) methyl) -5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (18)

White powder, 17 mg, 66% yield, \([\alpha]_}^\) + 167.35 (c 0.034, MeOH);1H NMR (400 MHz, CD3OD) δ 7.20-7.06 (m, 4H, H-5′, H-6′, H-7′, H-8′), 6.72 (s, 1H, H-15), 6.58 (s, 1H, H-1), 6.31 (s, 1H, H-4), 6.26 (s, 1H, H-12), 5.01 (s, 1H, H-8), 3.36 (s, 2H, H-3′), 3.34 (d, J = 14.0 Hz, 1H, H-18a), 3.11 (d, J = 14.0 Hz, 1H, H-18b), 3.05-3.03 (m, 1H, H-7), 2.83-2.79 (m, 2H, H-1′),2.59-2.55 (m, 6H, H-1′, H-2′), 2.31 (s, 3H, 10′), 2.04 (s, 3H, H-19), 1.99 (s, 3H, H-16), 1.50 (d, J = 7.2 Hz, 3H, H-17);13C NMR (100 MHz, CD3OD) δ 153.3 (C-11), 149.9 (C-2), 148.7 (C-14), 146.7 (C-5), 137.6 (C-4′), 136.6 (C-6′), 130.2 (C-5′), 127.8 (C-7′), 127.7 (C-8′), 127.3 (C-13), 127.2 (C-6), 126.6 (C-9′), 125.8 (C-10), 122.2 (C-3), 119.3 (C-4), 111.9 (C-1), 110.6 (C-12), 109.5 (C-15), 89.5 (C-8), 89.1 (C-9), 64.0 (C-18), 62.7 (C-3′), 54.3 (C-1′), 53.0 (C-2′), 32.4 (C-7), 20.0 (C-10′), 15.4 (C-19), 14.5 (C-17), 12.3 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C31H36N2O4]+ 501.2748, found 501.2711.

(5aS,10aR,11R)-3,8,11-trimethyl-5a-((4-(pyrimidin-2-yl)piperazin-1-yl) methyl) -5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (19)

White powder, 16 mg, 69% yield, \([\alpha]_}^\) + 172.05 (c 0.083, MeOH); 1H NMR (400 MHz, CDCl3) δ 8.31 (d, J = 4.8 Hz, 2H, H-4′), 6.72 (s, 1H, H-15), 6.57 (s, 1H, H-1), 6.49 (t, J = 4.8 Hz, 1H, H-5′), 6.40 (s, 1H, H-4), 6.36 (s, 1H, H-12), 5.08 (d, J = 3.2 Hz, 1H, H-8), 3.80-3.75 (m, 4H, H-2′), 3.20 (d, J = 14.0 Hz, 1H, H-18a), 3.13-3.10 (m, 1H, H-7), 2.91-2.85 (m, 2H, H-1′), 2.80 (d, J = 14.0 Hz, 1H, H-18b), 2.60-2.55 (m, 2H, H-1′), 2.09 (s, 3H, H-19), 2.04 (s, 3H, H-16), 1.51 (d, J = 6.8 Hz, 3H, H-17); 13C NMR (100 MHz, CDCl3) δ 161.4 (C-3′), 157.8 (C-4′), 153.8 (C-11), 149.1 (C-2), 148.0 (C-14), 147.3 (C-5), 127.5 (C-13), 127.0 (C-6), 126.2 (C-10), 122.1 (C-3), 119.9 (C-4), 112.7 (C-1), 111.5 (C-12), 110.1 (C-15), 109.8 (C-5′), 89.7 (C-8), 89.1 (C-9), 64.9 (C-18), 55.1 (C-1′), 44.2 (C-2′), 32.7 (C-7), 16.5 (C-19), 15.6 (C-16), 13.4 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C27H31N4O4]+ 475.2340, found 475.2311.

(5aS,10aR,11R)-3,8,11-trimethyl-5a-((4-(pyrazin-2-yl)piperazin-1-yl)methyl)-5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (20)

White powder, 14 mg, 59% yield, \([\alpha]_}^\) + 173.60 (c 0.135, MeOH); 1H NMR (400 MHz, CDCl3) δ 8.07-8.06 (m, 2H, H-5′, H-6′), 7.82 (d, J = 2.8 Hz, 1H, H-4′), 6.76 (s, 1H, H-15), 6.59 (s, 1H, H-1), 6.41 (s, 1H, H-4), 6.35 (s, 1H, H-12), 5.06 (d, J = 2.8 Hz, 1H, H-8), 3.52-3.50 (m, 4H, H-2′), 3.18 (d, J = 14.0 Hz, 1H, H-18a), 3.11-3.05 (m, 1H, H-7), 2.92-2.87 (m, 2H, H-1′), 2.84 (d, J = 14.0 Hz, 1H, H-18b), 2.66-2.62 (m, 2H, H-1′), 2.10 (s, 3H, H-19), 2.04 (s, 3H, H-16), 1.51 (d, J = 7.2 Hz, 3H, H-17); 13C NMR (100 MHz, CDCl3) δ 155.1 (C-3′), 153.7 (C-11), 149.5 (C-14), 148.3 (C-2), 147.1 (C-5), 142.0 (C-6′), 132.4 (C-5′), 130.6 (C-4′), 127.4 (C-13), 127.4 (C-6), 126.0 (C-10), 122.4 (C-3), 119.8 (C-4), 112.7 (C-1), 111.4 (C-12), 110.4 (C-15), 89.7 (C-8), 89.0 (C-9), 64.7 (C-18), 54.6 (C-2′), 44.7 (C-1′), 32.7 (C-7), 16.6 (C-19), 15.7 (C-16), 13.4 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C27H30N4O4]+ 475.2340, found 475.2341.

(5aS,10aR,11R)-3,8,11-trimethyl-5a-((4-(quinolin-2-yl)piperazin-1-yl)methyl) -5a,10a-dihydro-11H-benzofuro[3,2-b]chromene-2,7-diol (21)

White powder, 12 mg, 56% yield, \([\alpha]_}^\) + 175.09 (c 0.099, MeOH); 1H NMR (400 MHz, CDCl3) δ 7.86 (d, J = 9.2 Hz, H-5′), 7.74 (d, J = 8.4 Hz, H-7′), 7.59 (d, J = 8.0 Hz, H-7′), 7.52 (dd, J = 7.2, 7.2 Hz, 1H, H-9′), 7.23 (dd, J = 7.6, 7.2 Hz, 1H, H-8′), 6.91 (d, J = 9.2 Hz, 1H, H-4′), 6.75 (s, 1H, H-15), 6.53 (s, 1H, H-1), 6.41 (s, 1H, H-4), 6.35 (s, 1H, H-12), 5.08 (d, J = 2.8 Hz, 1H, H-8), 3.70-3.61 (m, 4H, H-2′), 3.14 (d, J = 14.0 Hz, 1H, H-18a), 3.11-3.08 (m, 1H, H-7), 2.91-2.86 (m, 2H, H-1′), 2.81 (d, J = 14.0 Hz, 1H, H-18b), 2.65-2.60 (m, 2H, H-1′), 2.08 (s, 3H, H-19), 2.04 (s, 3H, H-16), 1.47 (d, J = 7.2 Hz, 3H, H-17); 13C NMR (100 MHz, CDCl3) δ 157.7 (C-3′), 153.8 (C-11), 149.1 (C-2), 147.9 (C-14), 147.6 (C-5), 147.3 (C-11′), 137.7 (C-5′), 129.8 (C-9′), 127.5 (C-13), 127.3 (C-7′), 127.2 (C-6), 126.3 (C-10), 126.2 (C-8′), 123.1 (C-3), 122.6 (C-8′), 122.3 (C-6′), 119.8 (C-4), 112.8 (C-4′), 111.5 (C-1), 110.4 (C-12), 109.9 (C-15), 89.7 (C-8), 89.0 (C-9), 64.6 (C-18), 55.0 (C-1′), 45.6 (C-2′), 32.7 (C-7), 16.6 (C-19), 15.6 (C-16), 13.4 (C-17); HRMS (ESI, m/z): [M + H]+ calcd for [C32H34N3O4]+ 524.2544, found 524.2516.

BiologyIn vitro MT agonistic activity evaluation

Referring to our previous paper [7], HEK293 cell lines that stably express human MT1 or MT2 receptor were cultured in Dubecco’s modified Eagle’s medium supplemented with 10% fetal bovine serum at 37 °C under 95% O2 /5% CO2. The cells were incubated in a Matrigel coated 96-well black plate with a plating volume of 100 μL/well and density of 4 × 104/well, and incubated in a CO2 incubator (Thermo Forma 3310, Gaithersburg, USA.) overnight. The cells were then dyed with an HDB wash free calcium assay kit, and placed in a CO2 incubator for 1 h. (+) and (−)-paeoveitols and their derivatives were dissolved in 10 μL DMSO and 990 μL HBSS buffer, and a plating volume of 100 μL/well was extracted in a Matrigel coated 96-well clear bottom plate. Placing two 96-well plates into Flexstation 3 Benchtop Multi-Mode Microplate Reader, reading absorption values at room temperature using Flexstation 3 Benchtop Multi-Mode Microplate Reader with wavelength (excitation: 485 nm; emission:525 nm; emission cut-off: 515 nm). EC50 values for derivative 13 were determined from the dose-response curves obtained with seven concentrations from the range of 0.02 to 2 mM using GraphPad Prism 6.0.

Forced swim test (FST)

Male Kunming mice (weight 15−18 g) were purchased from Beijing Hengfu Biotechnology Co., Ltd with license number: SCXK (JING) 2020-0009, Beijing, China). All mice were placed in a group of six animals per cage that could freely access food and water with an ambient temperature of 22 ± 1 °C, and a relative humidity of 55−65% under a normal 12 h light/dark cycle (light turned on at 7 am).

The forced swim test was performed following a literature method [20]. Mice were individually placed into 25 cm high, 15 cm diameter glass cylinders filled with 10 cm high water, and the temperature was maintained at 25 ± 1 oC. Mice were gently placed onto the water and forced to swim for 6 min, and the total time of the last 4 min of immobility was automatically measured by the ANY-maze Video Tracking System (Anymaze, Stoelting Co., Wood Dale, USA).

Neurochemical tests

After continuous administration of vehicle or compound 13 (20 mg/kg) for 14 days, male Kunming mice were executed by cervical dislocation, and brains were collected and rapidly dissected on an ice-cold glass plate to isolate the frontal cortex, hippocampus, striatum, hypothalamus, and thalamus. Weighed tissue samples were homogenized in an ice-cold solution of 0.2 M perchloric acid (10 μ/mg) containing 0.1 mM EDTA, and then centrifuged at 15,000 rpm for 20 min at 4 °C. The supernatant was collected and the amounts of NE, 5-HT, 5-HIAA, DA, and DOPAC were measured by HPLC-ECD equipped with an Agilent 1200 pump (0.6 mL/min) and electrochemical detector (+0.50 V). The mobile phase was 69 mM sodium dihydrogen phosphate, 0.01% (v/v) Et3N, 0.025 mM EDTA, 1.7 mM sodium octanesulfonate (pH = 3.0) and 12% methanol. The injection volume was 20 μL.

In silico ADMET properties and drug-likeness prediction

The structures of compound 13 and (+)-paeoveitol were drawn using ChemDraw software (ChemDraw® Ultra, version 12), saved separately as an MDL Mol file (*.mol), and upload to the SwissADME server and converted into SMILES format. After that, the “Run” icon was pressed to give the ADMET parameters and related values.

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