Reagents were purchased from Fisher Scientific, VWR International, Sigma Aldrich, and Combi-Blocks, Inc. Chromatographic purification of compounds (normal phase and reverse phase) were carried out on a Teledyne Isco Combiflash RF system. H-NMR spectra were obtained on a Bruker 400-MHz NMR. Chemical shift values ( values) were reported in ppm relative to TMS. For multiplicity, s = singlet, d = doublet, t = triplet, m = multiplet. Purity (%) and mass spectral data were determined with a Waters Agilent 1200 HPLC/MS (Zorbax SB-C18, 2.1 x 30 mm, 3.5 μm, 100% water/0.1% formic acid to 100% acetonitrile/0.1% formic acid over 4.0 minutes, 1.0 mL/min.) with a diode array detector from 210-400 nm and Agilent 6130 quadrupole MS. All compounds were purified to 95% purity or greater as determined by HPLC/MS and 1H-NMR. Melting points were recorded on a capillary melting point apparatus.
Methyl 2,2-dimethylpent-4-enoate (4, R1a, R1b = Me): This reaction was performed in oven-dried glassware under a nitrogen atmosphere. To a well-stirred solution of freshly prepared lithium diisopropylammide (1M, 1.10 equiv) in dry 35 ml tetrahydrofuran, isobutyric acid methyl ester (3.32 g, 32.6 mmol, 1.0 equiv) was added dropwise during 0.5 hours at -78 oC. The mixture was allowed to stir at this temperature for 30 min followed by the addition of allyl bromide (5.35 g, 44.0 mmol) and Hexamethylphosphoramide (HMPA) (2.91 g, 16.3 mmol) dropwise over 0.5 h. The reaction mixture was stirred overnight at room temperature, quenched with 10% HCl (while cooling in ice bath) until acidic (pH = 2). The organic layer was separated and the aqueous layer was extracted with hexanes (3 x 100mL). The extract was washed with 10% NaHCO3 (200mL) and brine (200mL). The solution was then dried over MgSO4, concentrated in vacuo and distilled (bp. 85.5~86.5 oC/3.5mm Hg) to provide 3.47g (75% yield) of the product as a colorless oil. 1H NMR (400 MHz, CDCl3) δ 5.73 (1H, dd, J = 9.4, 17.7, H-4), 5.04 (2H, dd, J = 1.9, 13.5, H-5), 4.12 (3H, s, OCH3), 2.28 (2H, d, J = 7.4, H-3), 1.17 (6H, s, H-2’); 13C NMR (101 MHz, CDCl3) δ 177.42 (C=O), 134.42 (CH, C-4), 117.88 (CH2, C-5), 60.35 (CO2CH3) 44.91 (C, C-2), 42.25 (CH2, C-3), 24.92 (CH(CH3)2, C-2)
Ethyl 2,2-diethylpent-4-enoate (4, R1a, R1b = Et): The title compound was prepared according to the procedure for methyl 2,2-dimethylpent-4-enoate, except 2-ethyl-butyric acid ethyl ester was substituted for isobutyric acid methyl ester. The product was isolated as a colorless oil. (66% yield) 1H NMR (400 MHz, CDCl3) δ 5.68 (1H, dd, J = 9.9, 17.2, H-4), 5.16 – 4.97 (2H, m, H-5), 4.14 (2H, q, J = 7.1, OCH2CH3), 2.33 (2H, d, J = 7.4, H-3), 1.59 (6H, dt, J = 6.5, 7.5, H-3’), 1.26 (3H, t, J = 7.1, OCH2CH3), 0.80 (6H, t, J = 7.5, H-4’). 13C NMR (101 MHz, CDCl3) δ 175.6 (CO), 135.5 (CH, C-4), 116.2 (CH2, C-5), 61.8 (CH2), 46.3 (C, C-2), 32.2 (CH2, C-3), 29.8 (CH2, C-3’), 14.3 (CH3, OCH2CH3), 10.5 (CH3, C-4’).
5-(2-hydroxy-ethyl)-3,3-dimethyl-dihydro-furan-2-one: A mixture of glacial acetic acid (28.6 g, 477 mmol, 53.6 equiv), paraformaldehyde (0.80 g, 26.7 mmol, 3.0 equiv) and H2SO4 (0.5 g, 4.45 mmol, 0.57equiv) was stirred for 30min at 70 oC before methyl 2,2-dimethylpent-4-enoate (1.26 g, 8.9mmol, 1.0 equiv) was added dropwise during 10 min. The reaction mixture was then maintained at 70~80 oC and allowed to stir overnight. Acetic acid was removed under reduced pressure and the reaction was quenched with 10% NaHCO3 solution. The mixture was then extracted with ethyl acetate (3 x 50 mL) and the combined organic phase was concentrated in vacuo to give a crude oil. The crude oil was used for next step without further purification.
A mixture of the crude oil and 30% NaOH (7.1 g NaOH, 177 mmol, 20 equiv) aqueous solution was refluxed for 2 hours. The mixture was cooled in an ice bath and excess 30% H2SO4 was added until acidic (pH < 2). The resulting mixture was extracted with ethyl acetate (3 x 200 mL), the combined organic phase was washed with 10% NaHCO3, (400 mL), brine (400mL), dried over MgSO4 and concentrated in vacuo to give a crude product which was further purified by column chromatography (Ethyl acetate/Hexanes, 10% ~ 60%) to provide the product as a clear oil (1.05g, 73%). 1H NMR (400 MHz, CDCl3) δ 4.70-4.60 (1H, m, CH), 3.90-3.78 (2H, m, -CH2CH2OH), 2.22 (1H, dd, J = 5.9, 12.7, CH2), 1.98 – 1.87 (2H, m, -CH2CH2OH), 1.80 (1H, dd, J = 5.9, 12.7, CH2), 1.29 (3H, s, CH3), 1.28 (3H, s, CH3). 13C NMR (101 MHz, CDCl3) δ 182.26 (CO), 75.01 (CH), 59.58 (-CH2CH2OH), 43.93 (CH2), 40.62 (C(CH3)2), 38.69 (-CH2CH2OH), 25.31 (CH3), 24.61 (CH3); Rf, 0.34 (Hexane: Ethyl Acetate 1:1); Anal. Calcd for C8H14O3: C, 60.74; H, 8.92; Found: C, 60.47; H, 8.86.
Synthesis of 3,3-diethyl-5-(2-hydroxyethyl)dihydrofuran-2(3H)-one: The title compound was prepared according to the procedure for 5-(2-Hydroxy-ethyl)-3,3-dimethyl-dihydro-furan-2-one, except ethyl 2,2-diethylpent-4-enoate was substituted for methyl 2,2-dimethylpent-4-enoate. The product was isolated as a colorless oil. (76% yield): 1H NMR (400 MHz, CDCl3) δ 4.62 (dtd, J = 5.3, 7.3, 9.5, 1H), 3.78 (t, J = 6.1, 2H), 3.20 (s, 1H), 2.19 (dd, J = 6.8, 13.1, 1H), 1.97 – 1.81 (m, 3H), 1.70 – 1.56 (m, 4H), 0.93 (dt, J = 7.5, 20.7, 6H); 13C NMR (101 MHz, CDCl3) δ 181.46 (CO), 75.10 (CH), 58.91 (CH2CH2OH), 48.77 (C), 39.13 (CH2), 37.76 (CH2CH2OH), 29.21 (CH2CH3), 28.30 (CH2CH3), 8.83 (CH2CH3), 8.73 (CH2CH3); Rf, 0.36 (Hexane: Ethyl Acetate 5:2); Anal. Calcd for C10H18O3: C, 64.49; H, 9.74; Found: C, 64.20; H, 9.57.
2-(4,4-dimethyl-5-oxotetrahydrofuran-2-yl)ethyl 4-methylbenzenesulfonate: To a stirred solution of 5-(2-Hydroxy-ethyl)-3,3-dimethyl-dihydro-furan-2-one (0.316 g, 2 mmol, 1.0 equiv) and Et3N (0.152 g, 1.5 mmol, 1.5 equiv) in dry dichloromethane, a solution of p-TosCl (0.475 g, 2.5 mmol, 1.25 equiv) in dichloromethane was added drop wise at 0 oC. The resulting mixture was stirred at 0 oC for 1 hour and allowed to stir overnight at room temperature. Then, the reaction mixture was diluted with dichloromethane (50 mL), washed with 10 % HCl, brine, dried over MgSO4 and concentrated in vacuo to afford yellowish oil. This crude product was then purified by flash chromatography (silica gel; Ethyl acetate/Hexanes, 0% ~ 40%) to afford desired tosylate as a clear oil (424 mg, 67% yield). 1H NMR (400 MHz, CDCl3) δ 7.72 (2H, m, CH), 7.29 (2H, m, CH), 4.39 (1H, m, CH), 4.10 (2H, m, CH2CH2OTos), 2.38 (3H, s, CH3), 2.09 (1H, m, CH2), 1.93 (2H, m, CH2CH2OTos), 1.65 (1H, m, CH2), 1.16 (6H, s, CH3), 1.15 (6H, s, CH3);; 13C NMR (101 MHz, CDCl3) 13C NMR (101 MHz, CDCl3) δ 181.26 (CO), 145.16 (C), 132.53 (C), 130.03 (CH), 127.84 (CH), 72.93 (CH), 66.83 (CH2CH2O-SO2), 42.99 (CH2), 40.23 (C), 34.97 (CH2CH2O-SO2), 24.82 (CH3), 24.12 (CH3), 21.57 (CH3); HRMS (CI): [M+H] 313.1; Anal. Calcd for C15H20O5S: C, 57.67; H, 6.45; Found: C, 57.85; H, 6.63.
Synthesis of 2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl 4-methylbenzenesulfonate: The title compound was prepared according to the procedure for 2-(4,4-dimethyl-5-oxotetrahydrofuran-2-yl)ethyl 4-methylbenzenesulfonate, except 3,3-diethyl-5-(2-hydroxyethyl)dihydrofuran-2(3H)-one was substituted for 5-(2-Hydroxy-ethyl)-3,3-dimethyl-dihydro-furan-2-one, 69% yield. The product was isolated as a colorless oil. 1H NMR (400 MHz, CDCl3) δ 7.79 (2H, d, J = 8.3 Hz, CH), 7.36 (2H, d, J = 8.0 Hz, CH), 4.55 – 4.33 (1H, m, CH), 4.14 (2H, dd, J = 6.5, 13.3 Hz, CH2CH2OTos), 2.46 (3H, s, CH3), 2.21 – 1.84 (3H, m, CH2CH2OTos and CH2), 1.83 – 1.68 (1H, m, CH2), 1.58 (4H, t, J = 7.4 Hz, CH2CH3), 0.89 (6H, dt, J = 7.5, 18.0 Hz, CH2CH3); 13C NMR (101 MHz, CDCl3) δ 180.33 (CO), 145.30 (SO2-C), 132.72 (CCH3), 130.15 (CH), 128.03 (CH), 73.18 (CH), 66.95 (CH2CH2O-SO2), 48.67 (C), 37.53 (CH2), 35.82 (CH2CH2O-SO2), 29.14 (CH2CH3), 28.23 (CH2CH3), 21.76 (CH3), 8.81 (CH2CH3), 8.74 (CH2CH3). Anal. Calcd for C17H24O5S: C, 59.98; H, 7.11; Found: C, 60.27; H, 7.25.
2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q): 2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl 4-methylbenzenesulfonate (0.102 g, 0.3mmol, 1.0 equiv) was treated with 2-piperazin-1-yl-benzonitrile (168.3 mg, 0.9 mmol, 3.0 equiv) in dry tetrahydrofuran and refluxed for 72 hours. The tetrahydrofuran was evaporated under reduced pressure, the residue dissolved in dichloromethane, washed with H2O, and brine, then dried over MgSO4 and concentrated in vacuo to give a crude product which was purified by flash chromatography (silica gel; 2 % ~ 8 % MeOH in dichloromethane) to afford pure product as a yellow oil. (53.4 mg, 50% yield). 1H NMR (400 MHz, CDCl3) δ 7.62 – 7.42 (2H, m, CH), 7.01 (2H, dd, J = 7.8, 5.0 Hz, CH), 4.48 (1H, dq, J = 9.2, 6.7 Hz, CH), 3.35 – 3.17 (4H, m, NCH2CH2N), 2.81 – 2.51 (6H, m, NCH2CH2N and CH2CH2N), 2.14 (1H, dd, J = 13.1, 6.8 Hz, CH2), 1.86 (3H, m, CH2CH2N and CH2), 1.67 – 1.53 (4H, m, CH2CH3), 0.92 (6H, dt, J = 20.1, 7.5 Hz, CH2CH3); 13C NMR (101 MHz, CDCl3) δ 180.82 (CO), 155.57 (C), 134.43 (CH), 133.95 (CH), 122.03 (C-CN), 118.81 (CH), 118.50 (CH), 106.13 (C-CN), 75.50 (CH), 54.44 (C), 53.22 (NCH2CH2N), 51.34 (NCH2CH2N), 48.71 (NCH2CH2), 37.75 (CH2), 33.60 (NCH2CH2), 29.35 (CH2CH3), 28.39 (CH2CH3), 8.89 (CH2CH3), 8.81 (CH2CH3); MS (LC/MS, M+H+): 356.2.
3,3-diethyl-5-(2-(4-phenylpiperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9a): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 2-piperazin-1-yl-benzonitrile was substituted for 2-piperazin-1-yl-benzonitrile (50.6 mg, 51% yield): 1H NMR (400 MHz, D2O) δ 7.43 (2H, m, CH), 7.27 – 7.13 (3H, m, CH), 4.69 (1H, m, CH), 4.11 – 3.09 (10H, m, NCH2CH2N and CH2CH2N), 2.39 – 2.07 (3H, m, CH2CH2N and CH2), 1.98 (1H, dd, J = 13.4, 9.4 Hz, CH2), 1.61 (4H, m, CH2CH3), 0.87 (6H, dt, J = 12.1, 7.5 Hz, CH2CH3); 13C NMR (101 MHz, D2O) δ 187.92 (CO), 150.20 (C), 132.89 (CH), 127.03 (CH), 121.14 (CH), 79.53 (CH), 56.52 (C) , 54.13 (NCH2CH2N), 52.41 (NCH2CH2N), 50.87 (NCH2CH2), 39.37 (CH2), 32.81 (NCH2CH2), 31.91 (CH2CH3), 30.68 (CH2CH3), 11.00 (CH2CH3), 10.87 (CH2CH3); MS (LC/MS, M+H+): 331.2; Anal. Calcd for C20H32Cl2N2O2: C, 59.55; H, 8.00; N, 6.94; Found: C, 59.62; H, 8.11; N, 6.90. Melting point of di HCl salt: 239 oC
Synthesis of 3,3-dimethyl-5-(2-(4-phenylpiperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9b): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 2-(4,4-dimethyl-5-oxotetrahydrofuran-2-yl)ethyl 4-methylbenzenesulfonate was substituted for 4-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)butyl 4-methylbenzenesulfonate and 2-piperazin-1-yl-benzonitrile was substituted for 2-piperazin-1-yl-benzonitrile. The crude product was purified by flash chromatography (silica; MeOH:dichloromethane, 0% ~ 10%) to provide the product as an oil (50.9 mg, yield 56%). 1H NMR (400 MHz, CDCl3) δ 7.32 (2H, m, CH), 6.99 (2H, d, J= 7.9 Hz, CH), 6.91 (1H, t, J= 7.2 Hz, CH) 4.58 (1H, m, CH), 3.26 (4H, t, J= 5.0 Hz, NCH2CH2N), 2.66 (4H, m, NCH2CH2N), 2.61 (2H, m, CH2CH2N), 2.26 (1H, m, CH2), 1.90 (3H. m, CH2CH2N and CH2), 1.34 (3H, s, CH3), 1.33 (3H, s, CH3). 13C NMR (101 MHz, MeOD) δ 184.35 (CO), 152.68 (C), 130.07 (CH), 121.21 (CH), 117.49 (CH), 77.42 (CH), 55.67 (NCH2CH2N), 54.31 (CH2), 50.29 (NCH2CH2N), 44.18 (CH2CH2N), 41.71 (C(CH3)2), 33.74 (CH2CH2N), 25.27 (CH3), 24.59 (CH3). LC/MS [M+H]= m/z 303.2.
Synthesis of 3,3-diethyl-5-(2-oxo-2-(4-phenylpiperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9c): The title compounds was prepared according to the procedures described by R. Goa.18 1H NMR (400 MHz, MeOD) δ 7.80-7.68 (2H, m, CH), 7.67-7.49 (3H, m, CH), 4.09 (4H, broad, NCH2CH2N), 3.86-3.62 (4H, m, NCH2CH2N), 3.30 (1H, dt, J = 3.3, 1.6 Hz, CH), 2.95 (2H, ddd, J = 21.3, 16.2, 6.0 Hz, CH2), 2.34 (1H, dd, J = 13.3, 6.8 Hz, CH2), 2.03 (1H, dd, J = 13.3, 9.5 Hz, CH2), 1.77 – 1.49 (4H, m, CH2CH3), 0.94 (6H, dt, J = 18.7, 7.5 Hz, CH2CH3). 13C NMR (101 MHz, MeOD) δ 182.79 (CO), 170.27 (CO), 143.18 (C), 131.74 (CH), 131.40 (CH), 122.20 (CH), 75.73 (CH), 56.13 (C(CH2CH3)2), 49.93 (CH2), 44.34 (NCH2CH2N), 40.21 (NCH2CH2N), 39.68 (NCH2CH2N), 38.30 (CH2C(O)-N), 30.06 (CH2CH3), 29.14 (CH2CH3), 9.04 (CH2CH3), 8.93 (CH2CH3). MS (LC/MS, M+H+): 345.2
Synthesis of 4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)-1-phenylpiperazin-2-one (9d): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 1-phenylpiperazin-2-one was substituted for 2-piperazin-1-yl-benzonitrile (50.4 mg, yield 56%). The product was isolated as a clear oil. 1H NMR (400 MHz, CDCl3) δ 1H NMR (400 MHz, CDCl3) δ 7.42-7.34 (2H, m, CH), 7.31-7.21 (3H, m, CH), 4.51 (1H, m, CH), 3.75-3.61 (2H, m, NCH2CH2N), 3.29 (2H, dd, J= 13.3, 16.3 Hz, NCH0CO), 2.82 (2H, t, J= 5.7 Hz, CH2CH2N), 2.62 (2H, t, J= 7.0 Hz, NCH2CH2N), 2.14 (1H, dd, J= 6.8, 13.1 Hz, CH2), 1.89-1.78 (3H, m, CH2CH2N, CH2), 1.68-1.55 (4H, m, CH2CH3), 0.92 (6H, dt, J= 7.5, 21.0 Hz, CH2CH3). 13C NMR (101 MHz, CDCl3) δ 180.62 (CO), 141.54 (CO), 129.54 (C), 127.27 (CH), 125.91 (CH), 124.53 (CH), 74.86 (CH), 53.88 (C(CH2CH2)2), 50.80 (NCH2CH2N), 50.21 (NCH2CH2N), 49.43 (CH2), 48.62 (CH2CH2N), 37.6.2 (NCH2CO), 33.28 (CH2CH2N), 29.20 (CH2CH3), 28.25 (CH2CH3), 8.77 (CH2CH3), 8.70 (CH2CH3), LC/MS [M+H]= m/z 345.2
Synthesis of 3,3-diethyl-5-(2-(4-phenylpiperidin-1-yl)ethyl)dihydrofuran-2(3H)-one (9e): The title compound was prepared according to the procedure for 22-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 4-phenyl-piperidine was substituted for 2-piperazin-1-yl-benzonitrile (48.5 mg, 49% yield): 1H NMR (400 MHz, D2O) δ 7.39 (5H, tt, J = 7.3, 14.3,, CH), 4.71 (s, 1H), 3.72 (s, 2H), 3.36 (s, 2H), 3.17 (s, 2H), 2.98 (s, 1H), 2.37 (dd, J = 6.9, 13.4, 1H), 2.31 – 2.10 (m, 4H), 2.02 (dd, J = 9.4, 13.5, 3H), 1.78 – 1.53 (4H, m, CH2CH3), 0.92 (6H, dt, J = 7.5, 12.7, CH2CH3); 13C NMR (101 MHz, D2O) δ 187.89, 146.67, 131.85, 130.03, 129.64, 79.59, 52.33, 41.74, 39.25, 32.90, 31.85, 30.60, 10.89, 10.76; MS (LC/MS, M+H+): 330.2; Anal. Calcd for C21H32ClNO2 : C, 68.93; H, 8.81; N, 3.83; Found: C, 68.87; H, 8.93; N,3.79. Melting point of HCl salt: 239.5 oC
Synthesis of 5-(2-(4-cyclohexylpiperazin-1-yl)ethyl)-3,3-diethyldihydrofuran-2(3H)-one (9f): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 1-cyclohexyl-piperazine was substituted for 2-piperazin-1-yl-benzonitrile (56.6 mg, 56%). The product was isolated as a clear oil. 1H NMR (400 MHz, DMSO) δ 4.60 – 4.49 (m, 1H), 3.93 – 3.45 (m, 8H), 3.23 (s, 3H), 2.25 – 2.01 (m, 5H), 1.89 – 1.72 (m, 3H), 1.68 – 1.02 (m, 11H), 0.91 – 0.76 (m, 6H); 13C NMR (101 MHz, DMSO) δ 179.73, 74.15, 64.22, 52.26, 48.34, 47.85, 44.84, 36.45, 28.27, 27.60, 25.90, 24.57, 24.36, 8.54, 8.48; MS (LC/MS, M+H+): 337.3
Synthesis of 4-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9g): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 4-piperazin-1-yl-benzonitrile was substituted for 2-piperazin-1-yl-benzonitrile (48.mg, 45% yield): 1H NMR (400 MHz, MeOD) δ 7.69 – 7.54 (2H, m, CH), 7.23 – 7.02 (2H, m, CH), 4.59 (1H, ddd, J = 15.8, 9.3, 3.7 Hz, CH), 4.31 – 3.30 (10H, m, NCH2CH2N, NCH2CH2N, and CH2CH2N), 2.36 – 2.21 (2H, m, CH2), 2.21 – 2.06 (1H, m, CH2), 1.96 (1H, dd, J = 13.3, 9.4 Hz, CH2), 1.65 (4H, ddd, J = 17.4, 8.7, 6.2 Hz, CH2CH3), 0.95 (6H, dt, J = 13.3, 7.5 Hz, CH2CH3); 13C NMR (101 MHz, MeOD) δ 182.32 (CO), 153.74 (C), 134.73 (CH), 120.40 (CN), 116.55 (CH), 102.99 (C), 76.15 (CH), 54.93 (C(CH2CH2)2), 52.76 (NCH2CH2N), 49.91 (NCH2CH2N), 45.91 (CH2CH2N), 38.33 (CH2), 31.73 (CH2CH2N), 30.04 (CH2CH3), 29.17 (CH2CH3), 9.00 (CH2CH3), 8.91 (CH2CH3); MS (LC/MS, M+H+): 356.2; Anal. Calcd for C21H30ClN3O2: C, 64.35; H, 7.72; N, 10.72; Found: C, 64.46; H, 7.65; N, 10.65. Melting point of di-HCl salt: 213~214oC
Synthesis of 3,3-diethyl-5-(2-(4-(4-(trifluoromethyl)phenyl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9h): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q) except 1-(4-(trifluoromethyl)phenyl)piperazine was substituted for 2-piperazin-1-yl-benzonitrile, The product was isolated as a clear oil (Yield: 73%). 1H NMR (400 MHz, CDCl3) δ 7.48 (2H, d, J= 8.6 Hz, CH), 6.93 (2H, d, J= 8.6 Hz, CH), 4.50 (1H, m, CH), 3.29 (4H, t, J = 5.0 Hz, NCH2CH2N) 2.69-2.48 (6H, m, NCH2CH2N, and CH2CH2N), 2.15 (1H, dd, J= 6.8, 13.1 Hz, CH2), 1.98-1.78 (3H, m, CH2), 1.69-1.58 (4H, m, CH2CH3), 0.94 (6H, dt, J= 7.5, 19.0 Hz, CH2CH3) 13C NMR (101 MHz, MeOD) 183.18 (CO), 154.91 (C), 127.30 (CH), 125.01 (CF3), 115.75 (CH), 77.59 (CH), 55.95 (C(CH2CH2)2), 54.07 (NCH2CH2N), 50.13 (NCH2CH2N), 48.67 (CH2CH2N), 38.45 (CH2), 34.36 (CH2CH2N), 30.26 (CH2CH3), 29.32 (CH2CH3), 9.04 (CH2CH3), 8.95 (CH2CH3), LC/MS [M+H]= m/z 399.2
Synthesis of 5-(2-(4-(4-chlorophenyl)piperazin-1-yl)ethyl)-3,3-diethyldihydrofuran-2(3H)-one (9i): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 1-(4-chlorophenyl)piperazine was substituted for 2-piperazin-1-yl-benzonitrile. The product was isolated as a clear oil (Yield: 83%). 1H NMR (400 MHz, CDCl3) δ 7.20 (2H, d, J= 9.0 Hz, CH), 6.84 (2H, d, J= 9.0 Hz, CH), 4.49 (1H, m, CH), 3.17 (4H, t, J = 5.0 Hz, NCH2CH2N) 2.68-2.48 (6H, m, NCH2CH2N, and CH2CH2N), 2.15 (1H, dd, J= 6.9, 12.8 Hz, CH2), 1.96-1.77 (3H, m, CH2), 1.70-1.56 (4H, m, CH2CH3), 0.94 (6H, dt, J= 7.5, 19.2 Hz, CH2CH3) 13C NMR (101 MHz, MeOD) δ 183.16 (CO), 151.40 (C), 129.89 (CH), 125.55 (C), 118.53 (CH), 77.61 (CH), 55.51 (C(CH2CH2)2), 54.20 (NCH2CH2N), 50.12 (NCH2CH2N), 49.94 (CH2CH2N), 38.46 (CH2), 34.37 (CH2CH2N), 30.26 (CH2CH3), 29.33 (CH2CH3), 9.07 (CH2CH3), 8.98 (CH2CH3), LC/MS [M+H]= m/z 365.2.
Synthesis of 3,3-diethyl-5-(2-(4-(4-methoxyphenyl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9j): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 1-(4-methoxy-phenyl)-piperazinewas substituted for 2-piperazin-1-yl-benzonitrile. The product was isolated as a clear oil (67.1 mg, 62% yield). 1H NMR (400 MHz, CDCl3) δ 6.95 – 6.75 (4H, m, CH), 4.48 (1H, ddd, J = 19.8, 8.4, 6.4 Hz, CH), 3.76 (3H, s, CH3), 3.14 – 2.99 (4H, m, NCH2CH2N), 2.67 – 2.46 (6H, m, NCH2CH2N, and CH2CH2N), 2.15 – 2.07 (1H, m, CH2), 1.92 – 1.79 (3H, m, CH2), 1.62 (4H, qd, J = 7.4, 4.7 Hz, CH2CH3), 0.97 – 0.88 (6H, m, CH2CH3); 13C NMR (101 MHz, CDCl3) δ 180.90 (CO), 153.93 (C), 145.74 (C), 118.29 (CH), 114.53 (CH), 75.71 (CH), 55.67 (OCH3), 54.59 (C(CH2CH2)2), 53.51 (NCH2CH2N), 50.69 (NCH2CH2N), 48.72 (CH2CH2N), 37.81 (CH2), 33.91 (CH2CH2N), 29.35 (CH2CH3), 28.41 (CH2CH3), 8.90 (CH2CH3), 8.82 (CH2CH3). MS (LC/MS, M+H+): 361.2.
Synthesis of 3,3-diethyl-5-(2-(4-(p-tolyl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9k): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 1-p-tolyl-piperazine was substituted for 2-piperazin-1-yl-benzonitrile (52.8 mg, 51% yield): 1H NMR (400 MHz, MeOD) δ 7.25 – 7.13 (4H, m, CH), 4.62 – 4.45 (1H, m, CH), 4.05 – 3.28 (10H, m, NCH2CH2N, and CH2CH2N), 2.30 – 2.01 (6H, m, CH3 and CH2), 1.88 (1H, dd, J = 13.3, 9.4 Hz, CH2), 1.58 (4H, m, CH2CH3), 0.87 (6H, dt, J = 13.7, 7.5 Hz, CH2CH3); 13C NMR (101 MHz, MeOD) δ 182.36 (CO), 144.75 (C), 136.86 (C), 131.47 (CH), 119.95 (CH), 76.10 (CH), 54.89 (C(CH2CH2)2), 52.04 (NCH2CH2N), 50.53 (NCH2CH2N), 49.93 (CH2CH2N), 38.31 (CH2), 31.68 (CH2CH2N), 30.03 (CH2CH3), 29.17 (CH2CH3), 20.76 (CH3), 9.01 (CH2CH3), 8.92 (CH2CH3); MS (LC/MS, M+H+): 345.2; Anal. Calcd for C21H34Cl2N2O2: C, 60.43; H, 8.21; N, 6.71; Found: C, 60.33; H, 8.20; N, 6.61. Melting point of di-HCl salt: 213~217oC.
Synthesis of 3-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9l): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 3-(piperazin-1-yl)benzonitrile was substituted for 2-piperazin-1-yl-benzonitrile. In addition the crude product was purified by flash chromatography (silica; MeOH:dichloromethane, 0% ~ 10%). The product was isolated as a clear oil (Yield: 81%). 1H NMR (400 MHz, CDCl3) δ 7.30 (1H, m, CH), 7.09 (3H, m, CH), 4.49 (1H, m, CH), 3.22 (4H, t, J= 5.0 Hz, NCH2CH2N), 2.61 (4H, t, J= 5.2 Hz, NCH2CH2N), 2.56 (2H, m, CH2CH2N) 2.14 (1H, dd, J= 6.7, 13.1 Hz, CH2), 1.85 (3H, m, CH2), 1.62 (4H, m, CH2CH3) 0.92 (6H, dt, J= 7.7, 19.0 Hz, CH2CH3). 13C NMR (101 MHz, MeOD) δ 180.71 (CO), 151.13 (C), 129.92 (CH), 122.62 (CH), 119.94 (CH), 119.49 (CH), 118.47 (CN), 113.09 (CH), 75.36 (CH), 54.41 (C(CH2CH2)2), 52.83 (NCH2CH2N), 48.60 (NCH2CH2N), 48.07 (CH2CH2N), 37.67 (CH2), 33.54 (CH2CH2N), 29.22 (CH2CH3), 28.28 (CH2CH3), 8.77 (CH2CH3), 8.71 (CH2CH3). LC/MS [M+H]= m/z 356.20.
Synthesis of 3,3-diethyl-5-(2-(4-(3-(trifluoromethyl)phenyl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9m): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 1-(3-(trifluoromethyl)phenyl)piperazine was substituted for 2-piperazin-1-yl-benzonitrile. The product was isolated as a clear oil (Yield: 73%). 1H NMR (400 MHz, CDCl3) δ 7.42 (1H, t, J= 8.4 Hz, CH), 7.23 (1H, d, J= 8.1 Hz, CH), 7.10 (1H, s, CH), 7.09 (1H, dd, J= 2.2, 8.1 Hz, CH), 4.46 (1H. m, CH), 3.76 (4H. b, NCH2CH2N), 3.33 (4H, m, NCH2CH2N), 3.06 (2H, b, CH2CH2N), 2.28 (1H, m, CH2), 2.22 (1H, dd, J= 6.7, 12.6 Hz, CH2), 2.05 (1H, m, CH2), 1.86 (1H, dd, J= 9.4, 13.1 Hz, CH2), 1.63 (4H, m, CH2CH3) 0.92 (6H, dt, J= 7.4, 16.6 Hz, CH2CH3) 13C NMR (101 MHz, MeOD) δ 182.32 (CO), 151.54 (C), 132.87 (C), 132.55 (CH), 13126 (CF3), 121.08 (CH), 118.35 (CH), 114.01 (CH), 76.12 (CH), 54.90 (C(CH2CH2)2), 53.11 (NCH2CH2N), 49.94 (NCH2CH2N), 47.51 (CH2CH2N), 38.35 (CH2), 31.83 (CH2CH2N), 30.09 (CH2CH3), 29.19 (CH2CH3), 8.98 (CH2CH3), 8.90 (CH2CH3). LC/MS [M+H]= m/z 399.2.
Synthesis of 5-(2-(4-(3-chlorophenyl)piperazin-1-yl)ethyl)-3,3-diethyldihydrofuran-2(3H)-one (9n): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), 1-(3-chlorophenyl)piperazine was substituted for 2-piperazin-1-yl-benzonitrile. The product was isolated as a clear oil (Yield: 89%). 1H NMR (400 MHz, CDCl3) δ 7.04 (1H, t, J= 8.1 Hz, CH), 6.75 (1H, d, J= 2.1 Hz, CH), 6.67 (2H, td, J = 1.8, 8.2 Hz, CH), 4.37 (1H, m, CH), 3.08 (4H, t, J = 5.0 Hz, NCH2CH2N) 2.55-2.35 (6H, m, NCH2CH2N and CH2CH2N), 2.02 (1H, dd, J= 6.8, 13.0 Hz, CH2), 1.84-1.64 (3H, m, CH2), 1.56-1.46 (4H, m, CH2CH3), 0.81 (6H, dt, J= 7.5, 19.0 Hz, CH2CH3) 13C NMR (101 MHz, CDCl3) δ 180.61 (CO), 152.01 (C), 135.01 (CCl), 130.11 (CH), 119.60 (CH), 116.04 (CH), 114.09 (CH), 77.24 (CH), 75.29 (C(CH2CH2)2), 54.51 (NCH2CH2N), 52.87 (NCH2CH2N), 48.59 (CH2CH2N), 48.29 (CH2), 37.67 (CH2CH2N), 29.24 (CH2CH3), 28.29 (CH2CH3), 8.78 (CH2CH3), 8.71 (CH2CH3), LC/MS [M+H]= m/z 365.2
Synthesis of 3,3-diethyl-5-(2-(4-(o-tolyl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9o): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 1-(3-methylphenyl)piperazine was substituted for 2-piperazin-1-yl-benzonitrile. The product was isolated as a clear oil (Yield: 77%). 1H NMR (400 MHz, CDCl3) δ 7.20 (1H, t, J= 7.9 Hz, CH), 6.82 (1H, d, J= 7.6 Hz, CH), 6.76 (1H, s, CH), 6.75 (1H, d, J= 7.6 Hz, CH), 4.45 (1H, m, CH), 4.15-2.70 (10H, b, NCH2CH2N, NCH2CH2N, and CH2CH2N), 2.33 (3H, s, CH3), 2.28 (1H, m, CH2), 2.21 (1H, dd, J= 6.7, 13.1 Hz, CH2), 2.04 (1H, m, CH2), 1.85 1H, (dd, J= 9.3, 13.1 Hz, CH2), 1.63 (4H,, m, CH2CH3) 0.92 (6H, dt, J= 7.4, 16.8 Hz, CH2CH3) 13C NMR (101 MHz, MeOD) δ 182.29 (CO). 151.16 (C), 140.28 (CH), 130.22 (CCH3), 123.33 (CH), 118.77 (CH), 115.18 (CH), 76.10 (CH), 54.89 (C(CH2CH2)2), 53.35 (NCH2CH2N), 49.94 (NCH2CH2N),, 48.25 (CH2CH2N), 38.35 (CH2), 31.79 (CH2CH2N), 30.08 (CH2CH3), 29.19 (CH2CH3), 21.70 (CH3), 8.98 (CH2CH3), 8.90 (CH2CH3). LC/MS [M+H]= m/z 345.2.
Synthesis of 3,3-diethyl-5-(2-(4-(3-methoxyphenyl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9p): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 1-(3-methoxy-phenyl)-piperazine was substituted for 2-piperazin-1-yl-benzonitrile. The product was isolated as a clear oil (61.7 mg, 57% yield). 1H NMR (400 MHz, DMSO) δ 7.16 (1H. t, J = 8.2 Hz, CH), 6.65 – 6.35 (3H. m, CH), 4.54 (1H, s, CH), 3.82 (2H, d, J = 8.9 Hz, CH2), 3.57 (2H, s, CH2), 3.16 (6H, dd, J = 27.5, 16.8 Hz, NCH2CH2N and CH2CH2N), 2.28 – 2.04 (3H, m), 1.82 (1H, dd, J = 13.1, 9.4 Hz, CH2), 1.64 – 1.44 (4H, m, CH2CH3), 0.85 (6H, dt, J = 10.2, 7.5 Hz, CH2CH3); 13C NMR (101 MHz, MeOD) δ 182.37 (CO), 162.23 (COCH3), 149.87 (C), 131.32 (CH), 110.3 (CH), 106.9 (CH), 98.6 (CH), 76.14, 55.89 (COCH3), 54.87 (C(CH2CH2)2), 52.48 (NCH2CH2N), 49.92 (NCH2CH2N), 38.31 (CH2CH2N), 31.69 (CH2), 30.03 (CH2CH2N), 29.17 (CH2CH3), 9.01 (CH2CH3), 8.92 (CH2CH3). MS (LC/MS, M+H+): 361.2; Anal. Calcd for C21H34Cl2N2O3: C, 58.20; H, 7.91; N, 6.46; Found: C, 58.24; H, 7.93; N, 6.46.
Synthesis of 3,3-diethyl-5-(2-(4-(2-(trifluoromethyl)phenyl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9r): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 1-(2-(trifluoromethyl)phenyl)piperazine was substituted for 2-piperazin-1-yl-benzonitrile. In addition the crude product was purified by flash chromatography (silica; MeOH:dichloromethane, 0% ~ 10%). The product was isolated as a clear oil (Yield: 83%). 1H NMR (400 MHz, CDCl3) δ 7.62 (1H, d, J= 8.1 Hz, CH), 7.51 (1t, J= 7.7 Hz, CH), 7.38 (1H, d, J= 8.0 Hz, CH), 7.22 (1H, t, J= 7.7 Hz, CH), 4.50 (1H, m, CH), 2.97 (4H, t, J= 4.6 Hz, NCH2CH2N), 2.72-2.45 (6H, m, NCH2CH2N and CH2CH2N), 2.15 (1H, dd, J= 6.8, 13.1 Hz, CH2), 1.88 (3H, m, CH2), 1.64 (4H, m, CH2CH3) 0.94 (6H, dt, J= 7.5, 21.5 Hz, CH2CH3), 13C NMR (101 MHz, CDCl3) δ 178.91 (CO), 145.40 (C), 131.22 (CH), 125.86 (CF3), 125.58 (CCF3), 125.53 (CH), 123.67 (CH), 122.51 (CH), 73.63 (CH), 52.93 (C(CH2CH2)2), 51.79 (NCH2CH2N), 49.81 (NCH2CH2N), 46.93(CH2CH2N), 35.99 (CH2), 31.95, (CH2CH2N) 27.61 (CH2CH3), 26.66 (CH2CH3), 7.12 (CH2CH3), 7.05 (CH2CH3), LC/MS [M+H]= m/z 399.20
Synthesis of 5-(2-(4-(2-chlorophenyl)piperazin-1-yl)ethyl)-3,3-diethyldihydrofuran-2(3H)-one (9s): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile (9q), except 1-(2-chlorophenyl)piperazine was substituted for 2-piperazin-1-yl-benzonitrile. The product was isolated as a clear oil (Yield: 80%). 1H NMR (400 MHz, CDCl3) δ 7.38 (1H, dd, J= 1.6, 8.2 Hz, CH), 7.25 (1H, dt, J= 1.4, 8.1 Hz, CH), 7.06 (2H, m, CH), 4.46 (1H, m, CH), 3.74 (2H, t, J= 10.3 Hz, NCH2CH2N), 3.45 (2H, m, NCH2CH2N), 3.39-3.20 (4H, m, NCH2CH2N), 3.12 (2H, m, CH2CH2N), 2.28 (1H. m, CH2), 2.21 (1H, dd, J= 6.9, 12.5 Hz, CH2), 2.05 (1H, m, CH2) 1.85 (1H, dd, J= 9.2, 13.6 Hz, CH2), 1.62 (4H, m, CH2CH3), 0.92 (6H, dt, J= 7.5, 17.2 Hz, CH2CH3) 13C NMR (101 MHz, MeOD) δ182.32 (CO), 148.54 (C), 131.81 (CH), 130.05 (CCl), 129.26 (CH), 128.46 (CH), 122.03 (CH), 76.13 (CH), 54.99 (C(CH2CH2)2), 53.75 (NCH2CH2N), 49.94 (NCH2CH2N), 49.86 (CH2CH2N), 38.35 (CH2), 31.84 (CH2CH2N), 30.08 (CH2CH3), 29.21 (CH2CH3), 8.99 (CH2CH3), 8.91 (CH2CH3) LC/MS [M+H]= m/z 365.20.
Synthesis of 3,3-diethyl-5-(2-(4-(o-tolyl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9t): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile, except 1-o-Tolyl-piperazine was substituted for 2-piperazin-1-yl-benzonitrile (46.6 mg, 45% yield): 1H NMR (400 MHz, MeOD) δ 7.21 – 6.90 (4H. m, CH), 4.62 – 4.45 (1H, m, CH), 3.65 (2H, dd, J = 9.6, 5.4 Hz, NCH2CH2N), 3.43 – 3.26 (4H, m, NCH2CH2N), 3.24 – 3.07 (4H, m, NCH2CH2N and CH2CH2N), 2.34 – 2.02 (6H, m, CH3 and CH2), 1.90 (1H, dd, J = 13.3, 9.4 Hz, CH2), 1.60 (4H, ddd, J = 17.2, 8.6, 6.4 Hz, CH2CH3), 0.89 (6H, dt, J = 14.0, 7.5 Hz, CH2CH3); 13C NMR (101 MHz, MeOD) δ 182.40 (CO), 150.67 (C), 134.07 (CCH3), 132.33 (CH), 127.96 (CH), 125.84 (CH), 120.39 (CH), 76.21 (CH), 54.96 (C(CH2CH2)2), 54.81 (NCH2CH2N), 53.99 (NCH2CH2N), 53.80 (CH2CH2N), 50.26 (CH2), 49.93 (CH2CH2N), 38.33 (CH2CH3), 31.77 (CH2CH3), 30.05 (CH2CH3), 29.18 (CH2CH3), 17.84 (CH3), 9.01 (CH2CH3), 8.92 (CH2CH3); MS (LC/MS, M+H+): 345.3. melting point of di-HCl salt 233oC
Synthesis of 3,3-diethyl-5-(2-(4-(2-methoxyphenyl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9u): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile, except 1-(2-methoxy-phenyl)-piperazine was substituted for 2-piperazin-1-yl-benzonitrile (61.7 mg, 57% yield): 1H NMR (400 MHz, D2O) δ 7.06 (2H, ddd, J = 7.8, 7.2, 1.5 Hz, CH), 6.96 (1H, dd, J = 8.1, 1.3 Hz, CH), 6.93 – 6.82 (1H, m, CH), 4.50 (1H, dt, J = 9.2, 7.5 Hz, CH), 3.80 (3H, s, OCH3), 3.72 – 3.22 (10H, m, NCH2CH2N , NCH2CH2N and CH2CH2N), 2.28 – 2.10 (2H, m, CH2CH2N), 2.10 – 1.96 (1H, m, CH2), 1.86 (1H, dd, J = 13.3, 9.4 Hz, CH2), 1.68 – 1.42 (4H, m, CH2CH3), 1.00 – 0.75 (6H, m, CH2CH3); 13C NMR (101 MHz, D2O) δ 182.35 (CO), 153.90 (C), 138.69 (COCH3), 126.90 (CH), 122.35 (CH), 120.49 (CH), 113.32 (CH), 76.15 (CH), 56.21 (C(CH2CH2)2), 54.97 (NCH2CH2N), 53.20 (COCH3), 49.93 (NCH2CH2N), 49.35 (CH2CH2N), 38.35 (CH2), 31.74 (CH2CH2N), 30.05 (CH2CH3), 29.19 (CH2CH3), 9.00 (CH2CH3), 8.91 (CH2CH3); MS (LC/MS, M+H+): 361.2; Anal. Calcd for C21H34Cl2N2O3: C, 58.20; H, 7.91; N, 6.46; Found: C, 58.05; H, 7.95; N, 6.39. melting point of di-HCl salt: 228~229 oC
Synthesis of 3,3-diethyl-5-(2-(4-(2-isopropylphenyl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9v): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile, except 1-(2-Isopropyl-phenyl)-piperazinewas substituted for 2-piperazin-1-yl-benzonitrile. The product was isolated as a clear oil (44.8 mg, 40% yield). 1H NMR (400 MHz, DMSO) δ 7.30 (1H, dd, J = 7.4, 1.6 Hz, CH), 7.23 – 7.08 (3H, m, CH), 4.66 – 4.43 (1H, m, CH), 3.54 (2H, t, J = 9.6 Hz, NCH2CH2N, 3.41 (1H, dd, J = 13.7, 6.8 Hz, CH(CH3)2), 3.33 – 3.12 (6H, m, NCH2CH2N and NCH2CH2N), 3.02 (2H, d, J = 10.7 Hz, CH2CH2N), 2.31 – 2.03 (3H, m, CH2), 1.83 (1H, dd, J = 13.2, 9.3 Hz, CH), 1.69 – 1.34 (4H, m, CH2CH3), 1.16 (6H, d, J = 6.9 Hz, CH(CH3)2), 0.85 (6H, dt, J = 10.6, 7.5 Hz, CH2CH3); 13C NMR (101 MHz, DMSO) δ 179.77 (CO), 148.90 (C), 143.85 (C), 126.51 (CH), 125.20 (CH), 120.36 (CH), 74.31 (CH), 52.05 (C(CH2CH2)2), 51.57 (NCH2CH2N), 51.43 (NCH2CH2N), 49.55 (CH2CH2N), 47.87 (CH2), 36.43 (CH2CH2N), 29.72 (CH2CH3), 28.36 (CH2CH3), 27.66 (CH(CH3)2), 26.24 (CH(CH3)2), 23.99 (CH(CH3)2), 8.55 (CH2CH3), 8.51 (CH2CH3); MS (LC/MS, M+H+): 373.3.
Synthesis of 5-(2-(4-(2,4-dimethylphenyl)piperazin-1-yl)ethyl)-3,3-diethyldihydrofuran-2(3H)-one (9w): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile, except 1-(2,4-Dimethyl-phenyl)-piperazinewas substituted for 2-piperazin-1-yl-benzonitrile. The product was isolated as a clear oil (52.8 mg, 49% yield). 1H NMR (400 MHz, DMSO) δ 7.11 – 6.75 (3H, m, CH), 4.55 (1H, dt, J = 11.8, 8.4 Hz, CH), 3.53 (2H, m, CH2CH2N), 3.33 – 3.02 (8H, m, NCH2CH2N and NCH2CH2N), 2.31 – 2.07 (9H, m, CH2CH2N, CH3, CH3, and CH2), 1.83 (1H, dd, J = 13.2, 9.3 Hz, CH2), 1.67 – 1.39 (4H, m, CH2CH3), 0.85 (6H, dt, J = 10.6, 7.5 Hz, CH2CH3); 13C NMR (101 MHz, DMSO) δ 179.75 (CO), 147.31 (C), 132.64 (CCH3), 131.80 (CCH3), 131.62 (CH), 127.05 (CH), 118.82 (CH), 74.31 (CH), 52.11 (C(CH2CH2)2), 51.55 (NCH2CH2N), 51.38 (NCH2CH2N), 48.24 (CH2CH2N), 47.85 (CH2), 36.44 (CH2CH2N), 28.33 (CH2CH3), 27.64 (CH2CH3), 20.32 (CH3), 17.27 (CH3), 8.54 (CH2CH3), 8.49 (CH2CH3); MS (LC/MS, M+H+): 359.3
Synthesis of 3,3-diethyl-5-(2-(4-(pyridin-2-yl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9x): The title compound was prepared according to the procedure for 2-(4-(2-(4,4-diethyl-5-oxotetrahydrofuran-2-yl)ethyl)piperazin-1-yl)benzonitrile, except 1-pyridin-2-yl-piperazine was substituted for 2-piperazin-1-yl-benzonitrile. The product was isolated as a clear oil (41.8 mg, 42% yield). 1H NMR (400 MHz, D2O) δ 8.10 (1H, ddd, J = 9.1, 7.2, 1.8 Hz, CH), 8.02 (1H, dd, J = 6.2, 1.7 Hz, CH), 7.34 (1H, d, J = 9.2 Hz, CH), 7.12 (1H, t, J = 6.7 Hz, CH), 4.71 (1H, ddd, J = 16.0, 9.2, 3.6 Hz, CH), 4.31 – 3.26 (10H. m, NCH2CH2N, NCH2CH2N, and CH2CH2N), 2.26 (3H, m, CH2), 2.00 (1H, dd, J = 13.5, 9.4 Hz, CH2), 1.76 – 1.46 (4H. m, CH2CH3), 0.88 (6H, dt, J = 11.8, 7.5 Hz, CH2CH3); 13C NMR (101 MHz, D2O) δ 187.89 (CO), 155.57 (C), 147.93 (CH), 140.42 (CH), 117.97 (CH), 115.85 (CH), 79.49 (CH), 56.71 (C(CH2CH2)2), 53.74 (NCH2CH2N), 52.39 (NCH2CH2N), 46.15 (CH2CH2N), 39.38 (CH2), 31.88 (CH2CH2N), 30.66 (CH2CH3), 26.67 (CH2CH3), 10.99 (CH2CH3), 10.86 (CH2CH3); MS (LC/MS, M+H+): 332.2.
Synthesis of 3,3-diethyl-5-(2-(4-(pyridin-3-yl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9y): The title compound was prepared according to the procedure for 7-(2-(4-phenylpiperazin-1-yl)ethyl)-6-oxaspiro[3.4]octan-5-one, except 5-(2-bromoethyl)-3,3-diethyldihydrofuran-2(3H)-one was substituted for 2-(5-oxo-6-oxaspiro[3.4]octan-7-yl)ethyl 4-methylbenzenesulfonate and 1-(pyridin-3-yl)piperazine for 1-phenylpiperazine. The product was isolated as a clear oil (Yield: 44%). 1H NMR (400 MHz, CDCl3) δ 8.31 (1H, b, CH), 8.10 (1H, b, CH), 7.17 (2H, m, CH), 4.49 (1H, m, CH), 3.23 (4H, t, J = 5.3 Hz, NCH2CH2N) 2.68-2.48 (6H, m, NCH2CH2N, and CH2CH2N), 2.14 (1H, dd, J= 6.7, 13.0 Hz, CH2), 1.95-1.78 (3H, m, CH2CH2N and CH2), 1.69-1.57 (4H, m, CH2CH3), 0.93 (6H, dt, J= 7.5, 19.1 Hz, CH2CH3).13C NMR (101 MHz, CDCl3) δ 180.55 (CO), 146.48 (C), 140.96 (CH), 138.56 (CH), 123.58 (CH), 122.98 (CH), 75.12 (CH), 54.55 (C(CH2CH2)2), 52.68 (NCH2CH2N), 48.59 (NCH2CH2N), 47.72 (CH2CH2N), 37.64 (CH2), 32.89 (CH2CH2N), 29.23 (CH2CH3), 28.28 (CH2CH3), 8.77 (CH2CH3), 8.71 (CH2CH3). LC/MS [M+H]= m/z 332.2
Synthesis of 3,3-diethyl-5-(2-(4-(pyridin-4-yl)piperazin-1-yl)ethyl)dihydrofuran-2(3H)-one (9z): The title compound was prepared according to the procedure for 7-(2-(4-phenylpiperazin-1-yl)ethyl)-6-oxaspiro[3.4]octan-5-one, except 5-(2-bromoethyl)-3,3-diethyldihydrofuran-2(3H)-one was substituted for 2-(5-oxo-6-oxaspiro[3.4]octan-7-yl)ethyl 4-methylbenzenesulfonate and 1-(pyridin-4-yl)piperazine for 1-phenylpiperazine. The product was isolated as a clear oil (Yield: 37%). 1H NMR (400 MHz, CDCl3) δ 8.27 (2H, d, J= 5.7 Hz, CH), 6.67 (2H, d, J= 5.9 Hz, CH), 4.50 (1H, m, CH), 3.35 (4H, t, J = 5.2 Hz, NCH2CH2N) 2.68-2.46 (6H, m, NCH2CH2N, and CH2CH2N), 2.15 (1H, dd, J= 6.6, 13.0 Hz, CH2), 1.95-1.77 (3H, m, CH2), 1.69-1.57 (4H, m, CH2CH3), 0.93 (6H, dt, J= 7.5, 19.3 Hz, CH2CH3) 13C NMR (101 MHz, MeOD) δ 183.19 (CO), 157.31 (C), 148.03 (CH), 109.36, (CH) 77.54 (CH), 55.46 (C(CH2CH2)2), 53.71 (NCH2CH2N), 50.13 (NCH2CH2N), 46.71 (CH2CH2N), 38.43 (CH2), 34.38 (CH2CH2N), 30.25 (CH2CH3), 29.31 (CH2CH3), 9.05 (CH2CH3), 8.96 (CH2CH3) LC/MS [M+H]= m/z 332.2
Computational values: TPSA and cLogP values were calculated using the Dotmatics software suite (Dotmatics LLC The Old Monastery, Windhill Bishops, Stortford Herts, CW23 2ND UK).
Sigma-1 and sigma-2 competitive radioligand-binding studies: Competitive binding assays were conducted by the Psychoactive Drug Screening Program (PDSP) at The University of North Carolina, Chapel Hill under the direction of Professor Bryan Roth. Assay conditions can be found in the PDSP assay protocol book at https://pdsp.unc.edu/pdspweb/content/UNC-CH%20Protocol%20Book.pdf.
Aqueous solubility (pH 7.4) assay: Compounds were assessed for their solubility at pH 7.4 using the commercially available Millipore MultiScreenTM Solubility filter system (Millipore, Billerica, MA). Analysis was performed by liquid chromatography tandem mass spectrometry (LC/MS/MS).
Cytochrome P450 3A4 inhibition assay: Compounds were assessed for their ability to inhibit human cytochrome P450 3A4 using testosterone as a substrate and LC/MS/MS analysis. Expressed enzymes was used to minimize non-specific binding and membrane partitioning issues (McMasters et al., 2007).
Microsomal stability assays: Test compounds were assessed for microsomal stability by incubating them at 37 oC in the presence of mouse or human liver microsomes and an NADPH regenerating system as described by Yang et. al..19 Microsomal protein content was adjusted to give accurate rates of substrate consumption. Analysis was performed by Liquid Chromatography-tandem mass spectrometry (LC/MS/MS) analysis.
Table 1. In vitro screening and physicochemical properties data for (9a) – (9z)
Entry
|
R1a
|
R1b
|
X
|
Y
|
Z
|
R3
|
MW
|
TPSA
|
cLogP
|
σ2
|
σ1
|
σ2/σ1 ratio
|
HLM
|
MLM
|
Sol
|
CYP3A4
|
Ki (nM)
|
T ½ (min.)
|
mM
|
(IC50 nM)
|
9a
|
Et
|
Et
|
CH2
|
N
|
CH2
|
Ph
|
330
|
33
|
3.5
|
82
|
138
|
1.7
|
48
|
2
|
200
|
10000
|
9b
|
Me
|
Me
|
CH2
|
N
|
CH2
|
Ph
|
302
|
33
|
2.6
|
753
|
279
|
0.4
|
60
|
14
|
192
|
10000
|
9c
|
Et
|
Et
|
C(O)
|
N
|
CH2
|
Ph
|
344
|
50
|
3.3
|
10000
|
10000
|
1.0
|
39
|
3
|
189
|
10000
|
9d
|
Et
|
Et
|
CH2
|
N
|
C(O)
|
Ph
|
344
|
50
|
3.3
|
5289
|
10000
|
1.9
|
60
|
9.6
|
140
|
10000
|
9e
|
Et
|
Et
|
CH2
|
CH2
|
CH2
|
Ph
|
329
|
30
|
4.7
|
6.4
|
2.7
|
0.4
|
46
|
2
|
200
|
10000
|
9f
|
Et
|
Et
|
CH2
|
N
|
CH2
|
Cyc-hex
|
337
|
33
|
3.8
|
5.4
|
26
|
4.8
|
60
|
4.3
|
147
|
10000
|
9g
|
Et
|
Et
|
CH2
|
N
|
CH2
|
4-CN-Ph
|
355
|
57
|
3.2
|
34
|
98
|
2.9
|
24
|
3.5
|
200
|
8570
|
9h
|
Et
|
Et
|
CH2
|
N
|
CH2
|
4-CF3-Ph
|
398
|
33
|
4.5
|
7.3
|
14
|
1.9
|
11
|
3
|
25
|
10000
|
9i
|
Et
|
Et
|
CH2
|
N
|
CH2
|
4-Cl-Ph
|
365
|
33
|
4.1
|
12
|
17
|
1.4
|
12
|
2
|
88
|
10000
|
9j
|
Et
|
Et
|
CH2
|
N
|
CH2
|
4-OMe-Ph
|
361
|
42
|
3.4
|
53
|
79
|
1.5
|
60
|
5.4
|
185
|
10000
|
9k
|
Et
|
Et
|
CH2
|
N
|
CH2
|
4-Me-Ph
|
344
|
33
|
3.8
|
14
|
10000
|
714
|
41
|
2
|
200
|
10000
|
9l
|
Et
|
Et
|
CH2
|
N
|
CH2
|
3-CN-Ph
|
355
|
57
|
3.2
|
46
|
159
|
3.5
|
9.9
|
3.2
|
200
|
10000
|
9m
|
Et
|
Et
|
CH2
|
N
|
CH2
|
3-CF3-Ph
|
398
|
33
|
4.5
|
12
|
65
|
5.4
|
9.8
|
2.9
|
109
|
10000
|
9n
|
Et
|
Et
|
CH2
|
N
|
CH2
|
3-Cl-Ph
|
365
|
33
|
4.1
|
9.9
|
84
|
8.5
|
6.7
|
2.1
|
107
|
10000
|
9o
|
Et
|
Et
|
CH2
|
N
|
CH2
|
3-Me-Ph
|
344
|
33
|
3.8
|
30
|
59
|
2.0
|
15.2
|
2
|
200
|
10000
|
9p
|
Et
|
Et
|
CH2
|
N
|
CH2
|
3-OMe-Ph
|
360
|
42
|
3.4
|
62
|
169
|
2.7
|
37.8
|
2
|
200
|
10000
|
9q
|
Et
|
Et
|
CH2
|
N
|
CH2
|
2-CN-Ph
|
355
|
57
|
3.2
|
61
|
351
|
5.8
|
3.6
|
2
|
200
|
10000
|
9r
|
Et
|
Et
|
CH2
|
N
|
CH2
|
2-CF3-Ph
|
398
|
33
|
4.5
|
17
|
67
|
3.9
|
8.9
|
2
|
72
|
10000
|
9s
|
Et
|
Et
|
CH2
|
N
|
CH2
|
2-Cl-Ph
|
365
|
33
|
4.1
|
7.0
|
35
|
5.0
|
11
|
2
|
200
|
10000
|
9t
|
Et
|
Et
|
CH2
|
N
|
CH2
|
2-Me-Ph
|
344
|
33
|
3.8
|
9.3
|
36
|
3.9
|
22
|
2
|
194
|
7400
|
9u
|
Et
|
Et
|
CH2
|
N
|
CH2
|
2-OMe-Ph
|
360
|
42
|
3.4
|
44
|
1168
|
26.5
|
20
|
2.3
|
200
|
10000
|
9v
|
Et
|
Et
|
CH2
|
N
|
CH2
|
2-iPr-Ph
|
373
|
33
|
4.6
|
5.9
|
195
|
33.1
|
7.5
|
2.4
|
37
|
10000
|
9w
|
Et
|
Et
|
CH2
|
N
|
CH2
|
2,4-di-Me-Ph
|
359
|
33
|
4.0
|
9.2
|
10
|
1.0
|
27
|
2
|
126
|
10000
|
9x
|
Et
|
Et
|
CH2
|
N
|
CH2
|
2-Py
|
331
|
46
|
2.6
|
268
|
1499
|
5.6
|
46
|
2
|
200
|
10000
|
9y
|
Et
|
Et
|
CH2
|
N
|
CH2
|
3-Py
|
331
|
46
|
2.2
|
10000
|
10000
|
1.0
|
52
|
5.4
|
193
|
10000
|
9z
|
Et
|
Et
|
CH2
|
N
|
CH2
|
4-Py
|
331
|
46
|
2.2
|
142
|
10000
|
70.4
|
60
|
60
|
199
|
10000
|