HETEROCYCLES

Paper | Special issue | Vol. 80, No. 2, 2010, pp. 1249-1265
Received, 15th August, 2009, Accepted, 1st October, 2009, Published online, 1st October, 2009.
DOI: 10.3987/COM-09-S(S)112

■ Synthesis and Evaluation of Novel 3,4-Epoxypiperidines as Efficient DNA Alkylating Agents

Yuji Kawada, Tetsuya Kodama, Kazuyuki Miyashita, Takeshi Imanishi, and Satoshi Obika*

Graduate School of Pharmaceutical Science, Osaka University, 1-6 Yamadaoka, Suita, Osaka 560-0871, Japan

Abstract

3,4-Epoxypiperidine derivatives are novel DNA alkylating agents based on an active site of the antitumor antibiotics azinomycins A and B. A 3,4-epoxypiperidine library was constructed containing derivatives with a variety of functional groups at C5 via Huisgen reaction, and DNA cleavage activity was examined. Results revealed a more active derivative than any 3,4-epoxypiperidines previously reported.

INTRODUCTION
Azinomycins A and B are antitumor antibiotics which were isolated from Streptomyces griseofuscus S42227 in 1986 (Figure 1).1, 2 Azinomycins possess potent in vitro cell cytotoxicity and greater in vivo antitumor activity than mitomycin C.3,4 This bioactivity is derived from a 4-hydroxy-1-azabicyclo[3.1.0]hexane structure inherent in azinomycins.5,6 Therefore, compounds containing the 4-hydroxy-1-azabicyclo[3.1.0]hexane structure are predicted to function as a DNA alkylating agents. However, this structure is unstable, which makes synthesis of 4-hydroxy-1-azabicyclo[3.1.0]hexane derivatives difficult.7, 8,9,10
A previously proposed hypothesis suggests that interconversion between the 4-hydroxy-1-　azabicyclo[3.1.0]hexane structure and the 3,4-epoxypiperidine structure is possible (Figure 2). Based on this hypothesis, several 3,4-epoxypiperidine derivatives were synthesized, and some possessed significant DNA cleavage activity.11 A relation between structure and DNA-cleavage activity also confirmed that a

nitrogen atom and epoxide group are essential for DNA cleavage. These results supported the hypothesis and revealed the utility of 3,4-epoxypiperidine derivatives as DNA alkylating agents.
A previous report clarified that an aromatic substituent group at C5 played a significant role in DNA cleavage activity.11 Thus, the present study describes the construction of a library of 3,4-epoxypiperidine derivatives with various functional groups at C5 to determine if a more active compound can be synthesized.

RESULTS AND DISCUSSION
The Huisgen reaction, a 1,3-dipolar cycloaddition between an azide and alkyne, was chosen for synthesis of the 3,4-epoxypiperidine derivatives. The Huisgen reaction is a representative reaction of “click chemistry” as proposed by Sharpless et al.12 As azido and alkynyl groups are insensitive to several conditions, the Huisgen reaction is suitable for introduction of a functional group in the final stage of synthesis. In addition, a number of alkynes are commercially available. Therefore, the synthesis of a 3,4-epoxypiperidine derivative containing an azido group was planned for application of the Huisgen reaction.
Initially, an ethoxycarbonyl group of tetrahydropyridine 1, prepared from pyridine according to a method previously reported13, was exchanged for a 2-trimethylsilylethoxycarbonyl (Teoc) group, which can be easily removed under mild conditions. Introduction of an azido group into compound 2 was achieved using 4-azidobenzyl bromide prepared from 4-iodobenzyl alcohol via two steps.14,15 Finally,

epoxidation with MCPBA and separation of two diastereomers by silica gel column chromatography gave trans-4 and cis-4 as racemates in 40% and 15% yield, respectively. Determination of relative configuration was accomplished by comparison of 1H NMR spectra of trans-4 and cis-4 with that of the compounds previously reported.11
A previous report revealed that the trans isomer was more active than the cis isomer. Therefore, trans-4 was selected for reaction with several alkynes (Scheme 2, Table 1). In general, reactions of trans-4 with alkynes occurred smoothly with good yields as shown in Table 1. When trimethylsilyl acetylene was employed, elimination of a trimethylsilyl group was also observed to give the corresponding non-substituted triazole (Table 1, entry a). Because some aromatic alkynes, such as 1-, 2- and 9-ethynylanthracenes, are not soluble in the reaction media (t-BuOH : H2O = 1 : 1), reaction time was extended and product yields were moderate (Table 1, entries m, n, and o).　The resulting triazoles 5 were transformed into 3,4-epoxypiperidine derivatives 6 in good yields upon removal of the Teoc group.
DNA cleavage activity of the 3,4-epoxypiperidines was examined using a relaxation assay of supercoiled plasmid DNA.11 DNA damage transforms a supercoiled plasmid DNA (form I) into an open circular DNA (form II), which can be analyzed by agarose gel electrophoresis; a change in form alters the mobility on the agarose gel. The 3,4-epoxypiperidines 6a to 6o possessed several degrees of DNA cleavage activity. In particular, the derivatives containing aromatic rings at the C5 position showed significant improvement in DNA cleavage activity. These results indicate that the aromatic rings

functionas intercalators and enhance the affinity toward DNA. Interestingly, DNA cleavage of the benzyl derivative with the benzene ring connected to the triazole ring via a methylene bridge was not as great as that of derivatives with aromatic rings connected directly to the triazole ring (6f vs. 6g). This fact was more dramatic for 6h, i.e., the activity of 6h with an ethylene bridge was much weaker. These results demonstrate that the relative position of the aromatic ring and triazole structure is important for expression of activity. In compound 6f, the benzene ring and triazole ring may work cooperatively to intercalate into the DNA strand. In addition, the size of aromatic ring obviously affected the activity. The activities of the naphthyl derivatives 6k and 6l were greater than those of the phenyl derivative 6f, which acts at several µM, and melphalan (8), a clinically employed DNA alkylating agent.16 Anthracenyltriazoles 6m, 6n and 6o were less active than naphthyl triazoles 6k and 6l, indicating that the naphthyltriazolyl group is the best choice as the C5-substituent of the 3,4-epoxypiperidine derivative.
In conclusion, a 3,4-epoxypiperidine library 6a–6o was constructed via a Huisgen reaction and the DNA alkylating activity of the derivatives was evaluated. Results of relaxation assay of plasmid DNA revealed that naphthyl triazole derivatives 6k and 6l possessed more potent activity than previously reported 3,4-epoxypiperidine derivative 7 and the DNA alkylating agent, melphalan, used for cancer treatment. This result indicates that 3,4-epoxypiperidine derivatives show promise as anticancer therapy drugs.

EXPERIMENTAL
Unless otherwise mentioned, all chemicals from commercial sources were used without further purification. CH2Cl2 and triethylamine were distilled over calcium hydride. All reactions were conducted under a nitrogen atmosphere. Melting points were measured on a Yanagimoto micro melting point apparatus and are uncorrected. The 1H and 13C NMR spectra were recorded on JEOL EX-270 (1H, 270 MHz; 13C, 67.8 MHz), AL-300 (1H, 300 MHz; 13C, 75.5 MHz), ECS-400 (1H, 400 MHz; 13C, 100 MHz) instruments. Values of δ are in ppm relative to tetramethylsilane (0.00 ppm) or CDCl3 (7.26 ppm) as internal standards. The IR spectra were recorded on a JASCO FT/IR-4200 spectrometer. FAB-mass or EI-mass were measured on a JEOL JMS-600 or JMS-700 mass spectrometer. NALDI-mass was measured on Bruker Daitonics® Autoflex II TOF/TOF. Column chromatography was conducted using Fuji Silysia FL-100D, PSQ-100B silica gel.
4-Azidobenzyl bromide: 4-Iodobenzyl alcohol was converted to 4-azidobenzyl alcohol according to a previously reported method.14 To a solution of 4-iodobenzyl alcohol (5.0 g, 21 mmol) in DMSO (35 mL) and water (7 mL) was added CuI (410 mg, 2.1 mmol), sodium ascorbate (640 mg, 3.2 mmol), NaN3 (1.7 g, 26 mmol), and N,N-dimethylethylenediamine (94 mg, 120 µL, 1.1 mmol) at rt, and the resulting mixture stirred at the same temperature for 12 h. The reaction mixture was diluted with AcOEt and washed with water and brine. The organic layer was dried over Na2SO4 and concentrated under reduced pressure to give 4-azidobenzyl alcohol (3.1 g) as a yellow oil. To a stirred solution of 4-azidobenzyl alcohol (3.1 g) in CH2Cl2 (150 mL) was added phosphorus tribromide (2.8 g, 1.0 mL, 10 mmol) at 0°C, and the reaction mixture stirred for 20 min at the same temperature. After addition of ice water and extraction twice with CH2Cl2, the combined organic layers were washed with water and brine, dried over MgSO4, and concentrated under reduced pressure to afford 4-azidobenzyl bromide (3.7 g) as a brown oil, which was employed for the next reaction without purification; 1H NMR (400 MHz, CDCl3) δ: 4.48 (2H, s), 7.00 (2H, dt, J = 2.0, 8.5 Hz), 7.38 (2H, dt, J = 2.0, 8.5 Hz).15
(5RS)-5-Hydroxy-N-(2-trimethylsilyl)ethoxycarbonyl-1,2,5,6-tetrahydropyridine (2): A solution of compound 1 (5.0 g, 29.2 mmol) in EtOH (20 mL) and 5 N KOH solution (20 mL) was refluxed for 19 h, and the reaction solvent concentrated under reduced pressure. CH2Cl2 (30 mL) and N-[2-(trimethylsilyl)ethoxycarbonyloxy]succinimide (8.3 g, 32.1 mmol) was added to the residue. The reaction mixture was stirred for 45 min at room temperature, diluted with Et2O, and washed with water and brine. The organic layer was dried over MgSO4 and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (AcOEt : n-hexane = 1 : 2) to give 2 (4.9 g, 83%) as a pale yellow oil; IR νmax (KBr): 3414, 2953, 2896, 1700, 1433, 1356, 1234, 1178, 1159, 1113, 1063 cm-1; 1H NMR (300 MHz, CDCl3) δ: 0.39 (9H, s), 1.01 (2H, t, J = 7.5 Hz), 3.60 (2H, brs), 3.83 (1H, dd, J = 2.0, 16.0 Hz), 4.01–4.23 (2H, m), 4.20 (2H, t, J = 7.5 Hz), 5.85–5.94 (2H, m); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.9, 17.0, 42.4, 47.0, 61.9, 62.2, 124.4, 129.8, 154.5; Mass (FAB) m/z 244 (M+H+); HRMS (FAB) calcd for C11H22N1O3Si: 244.1369. Found: 244.1353.
(5RS)-5-(4-Azidobenzyloxy)-N-(2-trimethylsilyl)ethoxycarbonyl-1,2,5,6-tetrahydropyridine (3): To a stirred solution of 2 (4.2 g, 17.5 mmol) in DMF (60 mL) was added NaH (60% in oil, 1.40 g, 35 mmol) at 0°C and the mixture was stirred at the same temperature for 20 min. 4-Azidobenzyl bromide (3.7 g, 17.5 mmol) in DMF (60 mL) was added dropwise to the reaction mixture at 0°C, and stirred at rt for 1 h. After addition of water at 0°C, the resulting mixture was extracted twice with Et2O. The combined organic layers were washed with water and brine, dried over MgSO4, and concentrated under reduced pressure to give 3 (6.5 g) as a brown oil, which was used for the next reaction without further purification; 1H NMR (270 MHz, CDCl3) δ: 0.05 (9H, s), 1.01 (2H, t, J = 8.0), 3.58 (1H, brs), 3.77 (1H, brs), 3.96 (3H, brs), 4.20 (2H, t, J = 8.0 Hz), 4,51–­­4.64 (2H, m), 5.90 (2H, s), 7.00 (2H, d, J = 8.5 Hz), 7.35 (2H, d, J = 8.5 Hz); Mass (FAB) m/z 375 (M+H+); HRMS (FAB) calcd for C18H27N4O3Si: 375.1852. Found: 375.1830.
(3RS,4RS,5RS)-5-(4-Azidobenzyloxy)-3,4-epoxy-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (tnans-4): To a solution of 3 (6.6 g, 17.5 mmol) in CH2Cl2 (170 mL) was added MCPBA (9.1 g, 52.5 mmol) at rt and the resulting mixture stirred at the same temperature for 84 h. After addition of a mixture of saturated aqueous Na2S2O3 and saturated aqueous NaHCO3 (ca. 120 mL, 1 : 1), the reaction mixture was extracted with AcOEt. The organic layer was washed with saturated aqueous NaHCO3 solution, water, and brine, dried over Na2SO4, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (AcOEt : n-hexane = 1 : 4) to give trans-4 (2.9 g, 40% from 2) and cis-4 (1.1 g, 15% from 2) as pale yellow oils; trans-4; IR νmax (KBr): 2953, 2898, 2112, 1698, 1507, 1462, 1424, 1358, 1284, 1248, 1178, 1126, 1089 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.04 (9H, s), 1.01 (2H, t, J = 8.0 Hz), 3.27 (2H, s), 3.44–3.56 (2H, m), 3.86 (3H, brs), 4.18 (2H, t, J = 8 Hz), 4.56 (1H, d, J = 11.0 Hz), 4.70 (1H, d, J = 11.0 Hz), 7.02 (2H, d, J = 8.0 Hz), 7.36 (2H, d, J = 8.0 Hz); 13C NMR (67.8 MHz, DMSO-d6, 80 °C) δ: ‒1.9, 16.8, 41.3, 41.4, 49.3, 51.2, 62.4, 69.6, 69.7, 118.6, 128.9, 134.9, 138.4, 154.9; Mass (FAB) m/z 391 (M+H+); HRMS (FAB) calcd for C18H27N4O4Si: 391.1802. Found: 391.1775.
1-(3-Hydroxy-3-methyl-1-butynyl)anthracene: To a solution of 1-bromoanthracene (500 mg, 1.9 mmol) and 2-methyl-3-butyn-2-ol (330 mg, 0.38 mL, 3.9 mmol) in triethylamine (10 mL) were added CuI (3.7 mg, 19 µmol) and Pd(PPh3)2Cl2 (6.8 mg, 9.7 µmol), and the reaction mixture stirred at 80°C for 10 h. After removal of the solvent under reduced pressure, the resulting residue was purified by silica gel column chromatography (CHCl3 : n-hexane = 1 : 1) to give 1-(3-hydroxy-3-methyl-1-butynyl)anthracene (380 mg, 75%) as a yellow oil; IR νmax (KBr): 3347, 3050, 2980, 2928, 1613, 1456, 1373, 1314, 1268, 1225, 1163 cm-1; 1H NMR (400 MHz, CDCl3) δ: 1.82 (6H, s), 2.19 (1H, s), 7.38 (1H, t, J = 7.0 Hz), 7.49–7.52 (2H, m), 7.67 (1H, d, J = 7.0 Hz), 7.95 (1H, d, J = 8.0 Hz), 7.98–8.01 (1H, m), 8.07–8.09 (1H, m), 8.40 (1H, s), 8.84 (1H, s); 13C NMR (100 MHz, CDCl3) δ: 31.7, 65.9, 80.4, 99.1, 120.3, 124.4, 124.8, 125.7, 126.8, 127.9, 128.5, 129.1, 130.2, 130.9, 131.1, 131.8, 132.0; Mass (EI) m/z 260 (M+, 100), 245 (50), 242 (29), 202 (29); HRMS (EI) calcd for C19H16O: 260.1201. Found: 260.1211.
1-Ethynylanthracene: A mixture of 1-(3-hydroxy-3-methyl-1-butynyl)anthracene (380 mg, 1.4 mmol) and KOH (120 mg, 2.1 mmol) in toluene (15 mL) was heated under reflux for 1 h. After removal of the solvent under reduced pressure, the resulting residue was purified by silica gel column chromatography (CHCl3 : n-hexane = 1 : 1) to give 1-ethynylanthracene (225 mg, 78%) as a yellow solid; mp 68–70°C (EtOH); IR νmax (KBr): 3284, 3051, 1611, 1537, 1452, 1371, 1309 cm-1; 1H NMR (400 MHz, CDCl3) δ: 3.60 (1H,s), 7.41 (1H, dd, J = 7.0, 9.0 Hz), 7.49-7.53 (2H, m), 7.76 (1H, d, J = 6.5 Hz), 8.03 (2H, d, J = 9.0 Hz), 8.09–8.11 (1H, m), 8.45 (1H, s), 8.93 (1H, s); 13C NMR (100 MHz, CDCl3) δ: 82.0, 82.4, 119.8, 124.4, 124.9, 125.9, 125.9, 126.9, 128.0, 128.5, 129.7, 131.0, 131.1, 131.9, 132.2; Mass (EI) m/z 202 (M+, 100); HRMS (EI) calcd for C16H10: 202.0782. Found: 202.0783.
2-(3-Hydroxy-3-methyl-1-butynyl)anthracene: To a solution of 2-bromoanthracene (500 mg, 1.9 mmol) and 2-methyl-3-butyn-2-ol (330 mg, 0.38 mL, 3.9 mmol) in triethylamine (10 mL) were added CuI (3.7 mg, 19 µmol) and Pd(PPh3)2Cl2 (6.8 mg, 9.7 µmol), and the reaction mixture was stirred at 80°C for 10 h. After removal of the solvent under reduced pressure, the resulting residue was purified by silica gel column chromatography (CHCl3) to give 2-(3-hydroxy-3-methyl-1-butynyl)anthracene (175 mg, 35%) as a yellow solid; mp 188°C (EtOH); IR νmax (KBr): 3347, 2982, 2929, 1623, 1457, 1362, 1272, 1242, 1165 cm-1; 1H NMR (400 MHz, CDCl3) δ: 1.67 (6H, s), 2.06 (1H, s), 7.33 (1H, d, J = 9.0 Hz), 7.39 (2H, dd, J = 3.0, 6.5 Hz), 7.84 (1H, d, J = 9.0 Hz), 7.90 (1H, brs), 8.03 (1H, s), 8.28 (2H, d, J = 7.5 Hz); 13C NMR (100 MHz, CDCl3) δ: 31.5, 65.8, 82.7, 94.5, 119.4, 125.7, 125.8, 126.2, 126.2, 127.6, 128.1, 128.2, 128.2, 130.6, 130.9, 131.9, 132.0, 132.1; Mass (EI) m/z 260 (M+, 100), 245 (69), 202 (56); HRMS (EI) calcd for C19H16O: 260.1201. Found: 260.1208.
2-Ethynylanthracene: A mixture of 2-(3-hydroxy-3-methyl-1-butynyl)anthracene (135 mg, 0.52 mmol) and KOH (43 mg, 0.77 mmol) in toluene (5 mL) was heated under reflux for 1 h. After removal of the solvent under reduced pressure, the resulting residue was purified by silica gel column chromatography (CHCl3) to give 1-ethynylanthracene (96 mg, 92%) as a yellow solid; mp 175–176°C (EtOH); IR νmax (KBr): 3290, 3053, 1621, 1456, 1304, 1270, 1155 cm-1; 1H NMR (300 MHz, CDCl3) δ: 3.21 (1H,s),7.46–7.51 (3H, m), 7.96 (1H, d, J = 9.0 Hz), 8.00 (2H, brs), 8.21 (1H, s), 8.40 (1H, s); 13C NMR (100 MHz, CDCl3) δ: 77.9, 84.2, 118.7, 125.8, 125.9, 126.2, 126.4, 127.5, 128.1, 128.3, 128.3, 130.8, 132.0, 132.2, 132.9;Mass (EI) m/z 202 (M+, 100); HRMS (EI) calcd for C16H10: 202.0782. Found: 202.0785.
Typical procedure for preparation of 5(3RS,4RS,5RS)-3,4-Epoxy-5-[4-(1H-1,2,3-triazol-1-yl)benzyloxy]-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5a): To a solution of trans-4 (75 mg, 0.19 mmol) in t-BuOH (1.0 mL) and water (1.0 mL) were added CuSO4·5H2O (48 mg, 0.19 mmol), sodium ascorbate (76 mg, 0.38 mmol), and trimethylsilylacetylene (39 mg, 55 µL, 0.38 mmol) at rt, and the reaction mixture stirred at the same temperature for 27 h. The reaction mixture was extracted with AcOEt. The organic layer was washed with water and brine, dried over Na2SO4, and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (AcOEt : n-hexane = 1 : 1) to give 5a (68 mg, 85%) as a white paste; IR νmax (KBr): 2953, 1696, 1522, 1463, 1420, 1359, 1321, 1281, 1250, 1177, 1127, 1092, 1030 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.07 (9H, s), 1.01 (2H, t, J = 8.0 Hz), 3.31 (2H, brs), 3.48–3.60 (2H, m), 3.87 (3H, brs), 4.18 (2H, t, J = 8.0 Hz), 4.64 (1H, d, J = 11.5 Hz), 4.80 (1H, d, J = 11.5 Hz), 7.53 (2H, d, J = 7.5 Hz), 7.74 (2H, d, J = 7.5 Hz), 7.86 (1H, s), 7.99 (1H, s); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.0, 18.0, 42.3, 42.4, 50.3, 52.2, 63.4, 70.5, 70.8, 69.7, 120.8, 123.6, 129.4, 134.7, 136.8, 139.4, 155.8; Mass (FAB) m/z 417 (M+H+); HRMS (FAB) calcd for C20H29N4O4Si: 417.1958. Found: 417.1960.
(3RS,4RS,5RS)-3,4-Epoxy-5-[4-(4-methoxymethyl-1H-1,2,3-triazol-1-yl)benzyloxy]-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5b): a colorless oil; IR νmax (KBr): 2952, 1696, 1521, 1463, 1421, 1281, 1249, 1094, 1044, 1024 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.04 (9H, s), 1.00 (2H, t, J = 8.0 Hz), 3.31 (2H, brs), 3.47 (3H, s), 3.47–3.60 (2H, m), 3.87 (3H, brs), 4.18 (2H, t, J = 8.0 Hz), 4.63 (1H, d, J = 11.5 Hz), 4.82 (1H, d, J = 11.5 Hz), 7.52 (2H, d, J = 8.0 Hz), 7.73 (2H, d, J = 8.0 Hz), 7.97 (1H, s); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.0, 18.0, 42.3, 42.4, 50.3, 52.2, 58.0, 63.4, 65.7, 70.5, 70.8, 120.6, 122.5, 129.4, 136.7, 139.4, 145.7, 155.9; Mass (FAB) m/z 489 (M+H+); HRMS (FAB) calcd for C23H33N4O6Si: 489.2169. Found: 489.2168.
(3RS,4RS,5RS)-3,4-Epoxy-5-[4-(4-ethoxycarbonyl-1H-1,2,3-triazol-1-yl)benzyloxy]-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5c): a yellow oil; IR νmax (KBr): 2953, 2898, 1733, 1697, 1541, 1521, 1463, 1422, 1372, 1339, 1250, 1174, 1149, 1127, 1092 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.04 (9H, s), 1.01 (2H, t, J = 8.0 Hz), 1.45 (3H, t, J = 7.0 Hz), 3.31 (2H, brs), 3.43–3.65 (2H, m), 3.87 (3H, brs), 4.18 (2H, t, J = 8.0 Hz), 4.48 (2H, q, J = 7.0 Hz), 4.65 (1H, d, J = 11.0 Hz), 4.83 (1H, d, J = 11.0 Hz), 7.56 (2H, d, J = 8.0 Hz), 7.75 (2H, d, J = 8.0 Hz), 8.50 (1H, s); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.0, 14.7, 18.0, 42.3, 42.4, 50.3, 52.2, 61.2, 63.5, 70.5, 70.9, 121.2, 127.6, 129.4, 136.1, 140.2, 140.5, 155.9, 160.7; Mass (FAB) m/z 461 (M+H+); HRMS (FAB) calcd for C22H33N4O5Si: 461.2220. Found: 461.2225.
(3RS,4RS,5RS)-5-[4-(4-Cyclopropyl-1H-1,2,3-triazol-1-yl)benzyloxy]-3,4-epoxy-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5d): a colorless oil; IR νmax (KBr) : 2952, 1695, 1521, 1463, 1420, 1338, 1281, 1249, 1126, 1091, 1039 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.04 (9H, s), 0.93–1.03 (6H, m), 1.98–2.08 (1H, m), 3.30 (2H, brs), 3.48–3.63 (2H, m), 3.86 (3H, brs), 4.18 (2H, t, J = 8.0 Hz), 4.62 (1H, d, J = 11.5 Hz), 4.79 (1H, d, J = 11.5 Hz), 7.50 (2H, d, J = 8.0 Hz), 7.66 (1H, s), 7.69 (2H, d, J = 8.0 Hz); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.0, 7.0, 8.0, 18.0, 42.3, 42.4, 50.3, 52.2, 63.4, 70.6, 70.8, 119.4, 120.3, 129.3, 136.8, 139.0, 150.7, 156.0; Mass (FAB) m/z 457 (M+H+); HRMS (FAB) calcd for C23H33N4O4Si: 457.2271. Found: 457.2272.
(3RS,4RS,5RS)-5-[4-(4-Cyclohexyl-1H-1,2,3-triazol-1-yl)benzyloxy]-3,4-epoxy-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5e)
a colorless oil; IR νmax (KBr) : 2926, 2853, 1697, 1519, 1449, 1420, 1280, 1249, 1126, 1091, 1047 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.04 (9H, s), 1.00 (2H, t, J = 8.0 Hz), 1.37–1.51 (6H, m), 1.74–1.86 (2H, m), 2.11 (2H, brs), 2.86 (1H, brs), 3.30 (2H, brs), 3.44–3.59 (2H, m), 3.87 (3H, brs), 4.18 (2H, t, J = 8 Hz), 4.62 (1H, d, J = 11.0 Hz), 4.80 (1H, d, J = 11.0 Hz), 7.50 (2H, d, J = 8.0 Hz), 7.68 (2H, d, J = 8.0 Hz), 7.73 (1H, s); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.0, 18.0, 26.0, 26.2, 33.0, 35.3, 42.3, 42.4, 50.3, 52.2, 63.4, 70.6, 70.8, 119.3, 120.3, 129.3, 137.0, 139.0, 153.8, 155.9; Mass (FAB) m/z 499 (M+H+); HRMS (FAB) calcd for C26H30N4O4Si: 499.2741. Found: 499.2733.
(3RS,4RS,5RS)-3,4-Epoxy-5-[4-(4-phenyl-1H-1,2,3-triazol-1-yl)benzyloxy]-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5f): a white solid; mp 58–60°C (toluene : n-hexane = 1 : 3); IR νmax (KBr): 2953, 1697, 1522, 1460, 1419, 1281, 1250, 1124, 1090, 1042 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.05 (9H, s), 1.01 (2H, t, J = 8.0 Hz), 3.32 (2H, brs), 3.49–3.66 (2H, m), 3.87 (3H, brs), 4.20 (2H, t, J = 8 Hz), 4.65 (1H, d, J = 11.5 Hz), 4.70 (1H, d, J = 11.5 Hz), 7.31–7.56 (5H, m), 7.79 (2H, d, J = 8.0 Hz), 7.92 (2H, d, J = 8.0 Hz), 8.20 (1H, s); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.0, 18.0, 42.4, 42.4, 50.3, 52.2, 63.5, 70.6, 70.8, 120.0, 120.6, 126.1, 128.7, 129.4, 131.0, 136.0, 136.7, 139.5, 148.0, 155.9; Mass (FAB) m/z 493 (M+H+); HRMS (FAB) calcd for C26H33N4O4Si: 493.2271. Found: 493.2261; Anal. Calcd for C26H32N4O4Si: C, 63.39; H, 6.55; N, 11.37. Found: C, 63.16; H, 6.48; N, 11.35.
(3RS,4RS,5RS)-5-[4-(4-Benzyl-1H-1,2,3-triazol-1-yl)benzyloxy]-3,4-epoxy-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5g): a white paste; IR νmax (KBr): 2952, 1697, 1520, 1456, 1419, 1359, 1282, 1250, 1124, 1090, 1043, 1024 cm-1; 1H NMR (400 MHz, CDCl3) δ: 0.03 (9H, s), 1.00 (2H, t, J = 8.0 Hz), 3.29 (2H, brs), 3.44–3.61 (2H, m), 3.84–3.88 (3H, m), 4.17 (2H, t, J = 8 Hz), 4.18 (2H, s), 4.61 (1H, d, J = 12.0 Hz), 4.79 (1H, d, J = 12.0 Hz), 7.24–7.28 (1H, m), 7.32–7.34 (4H, m), 7.47 (2H, d, J = 8.0 Hz), 7.58 (1H, s), 7.68 (2H, d, J = 8.0 Hz); 13C NMR (75.45 MHz, DMSO-d6, 80°C) δ: ‒2.0, 17.0, 30.9, 41.3, 41.4, 49.3, 51.2, 62.4, 69.6, 69.8, 119.5, 120.2, 125.7, 127.9, 128.1, 128.3, 135.8, 138.2, 138.8, 146.7, 154.9; Mass (FAB) m/z 507 (M+H+); HRMS (FAB) calcd for C27H35N4O4Si: 507.2428. Found: 507.2426.
(3RS,4RS,5RS)-3,4-Epoxy-5-[4-(4-phenethyl-1H-1,2,3-triazol-1-yl)benzyloxy]-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5h): a colorless oil; IR νmax (KBr): 2952, 1696, 1520, 1455, 1420, 1281, 1249, 1126, 1091, 1045 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.04 (9H, s), 1.01 (2H, t, J = 8.0 Hz), 3.09 (2H, t, J = 5.5 Hz), 3.11 (2H, t, J = 5.5 Hz), 3.30 (2H, brs), 3.48–3.63 (2H, m), 3.87 (3H, brs), 4.18 (2H, t, J = 8.0 Hz), 4.62 (1H, d, J = 11.5 Hz), 4.80 (1H, d, J = 11.5 Hz), 7.21–7.30 (5H, m), 7.49–7.54 (3H, m), 7.67 (2H, d, J = 8.0 Hz); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.9, 17.1, 26.5, 34.3, 41.5, 41.5, 549.4, 51.3, 62.6, 69.7, 69.9, 119.5, 119.8, 125.6, 127.9, 127.9, 128.5, 136.0, 138.2, 140.8, 147.1, 155.0; Mass (FAB) m/z 521 (M+H+); HRMS (FAB) calcd for C28H37N4O4Si: 521.1584. Found: 521.2581.
(3RS, 4RS,5RS)-3,4-Epoxy-5-{4-[4-(2-pyridinyl) -1H-1,2,3-triazol-1-yl]benzyloxy}-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5i): colorless crystals; mp 110–111°C (toluene : n-hexane = 1 : 2); IR νmax (KBr): 2952, 1695, 1602, 1521, 1468, 1412, 1357, 1279, 1249, 1126, 1091, 1029 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.07 (9H, s), 1.00 (2H, t, J = 7.5 Hz), 3.30 (2H, brs), 3.43–3.60 (2H, m), 3.87 (3H, brs), 4.18 (2H, t, J = 7.5 Hz), 4.64 (1H, d, J = 10.0 Hz), 4.81 (1H, d, J = 10.0 Hz), 7.26 (1H, t, J = 7.0 Hz), 7.54 (2H, d, J = 6.5 Hz), 7.79–7.81 (2H, m), 8.25 (1H, d, J = 7.0 Hz), 8.59 (1H, s), 8.61 (1H, d, J = 7.0 Hz); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.0, 17.9, 42.3, 42.4, 50.3, 52.2, 63.4, 70.5, 70.8, 120.4, 120.8, 121.7, 123.7, 129.3, 136.6, 137.6, 139.6, 148.8, 150.1, 150.2, 155.8; Mass (FAB) m/z 494 (M+H+); Anal. Calcd for C25H31N5O4Si : C, 60.83; H, 6.33; N, 14.19. Found: C, 60.97; H, 6.28; N, 14.13.
(3RS,4RS,5RS)-3,4-Epoxy-5-{4-[4-(4-fluorophenyl)-1H-1,2,3-triazol-1-yl]benzyloxy}-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5j): a white solid; mp 97–99°C (toluene : n-hexane = 1 : 2); IR νmax (KBr): 2953, 1698, 1495, 1465, 1423, 1280, 1250, 1093, 1043 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.04 (9H, s), 1.01 (2H, t, J = 7.5 Hz), 3.31 (2H, brs), 3.48–3.59 (2H, m), 3.87 (3H, brs), 4.18 (2H, t, J = 7.5 Hz), 4.65 (1H, d, J= 11.5 Hz), 4.84 (1H, d, J = 11.5 Hz), 7.16 (2H, t, J = 8.5 Hz), 7.55 (2H, d, J = 8.0 Hz), 7.78 (2H, d, J = 8.0 Hz), 7.89 (2H, dd, J = 5.5, 8.5 Hz), 8.14 (1H, s); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.0, 18.0, 42.4, 42.4, 50.3, 52.2, 63.5, 70.6, 70.8, 116.4 (d, J = 22.0 Hz), 112.0, 120.6, 127.6 (d, J = 3.0 Hz), 128.1 (d, J = 8.5 Hz ), 129.4, 136.7, 139.6, 147.1, 155.9, 162.7 (d, J = 245.0 Hz); Mass (FAB) m/z 511 (M+H+); HRMS (FAB) calcd for C26H32FN4O4Si: 511.2177. Found: 511.2171.
(3RS,4RS,5RS)-3,4-Epoxy-5-{4-[4-(1-naphthyl) -1H-1,2,3-triazol-1-yl]benzyloxy}-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5k): a pale yellow foam; IR νmax (KBr): 2952, 1695, 1520, 1462, 1423, 1356, 1248, 1126, 1091, 1045 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.05 (9H, s), 1.02 (2H, t, J = 8.0 Hz), 3.30 (2H, brs), 3.50–3.65 (2H, m), 3.88 (3H, brs), 4.19 (2H, t, J = 8.0 Hz), 4.67 (1H, d, J = 12.0 Hz), 4.86 (1H, d, J = 12.0 Hz), 7.51‒7.59 (5H, m), 7.92–7.95 (5H, m), 8.25 (1H, s), 8.44 (1H, t, J = 5.0 Hz); 13C NMR (67.8 MHz, DMSO-d6, 80 °C) δ: ‒1.0, 18.0, 42.4, 42.5, 50.3, 52.2, 63.5, 70.6, 70.8, 120.8, 122.6, 126.0, 126.1, 126.6, 127.2, 127.7, 128.2, 128.9, 129.4, 129.4, 131.2, 134.3, 136.8, 139.5, 147.3, 155.9; Mass (FAB) m/z 543 (M+H+); HRMS (FAB) calcd for C30H35N4O4Si: 543.2428. Found: 543.2429.
(3RS,4RS,5RS)-3,4-Epoxy-5-{4-[4-(2-naphthyl) -1H-1,2,3-triazol-1-yl]benzyloxy}-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5l) a white solid; mp. 113–114°C (toluene : n-hexane = 1 : 3); IR νmax (KBr): 2953, 1698, 1520, 1464, 1418, 1250, 1117, 1042, 951 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.05 (9H, s), 1.02 (2H, t, J = 8.0 Hz), 3.31 (2H, brs), 3.45–3.61 (2H, m), 3.88 (3H, brs), 4.20 (2H, t, J = 8.0 Hz), 4.66 (1H, d, J = 11.5 Hz), 4.84 (1H, d, J = 11.5 Hz), 7.49–7.58 (4H, m), 7.81–8.00 (6H, m), 8.31 (1H, s), 8.43 (1H, s); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.0, 18.0, 42.4, 42.5, 50.3, 52.2, 63.5, 70.6, 70.9, 120.4, 120.6, 124.4, 124.5, 126.7, 127.1, 128.3, 128.5, 128.5, 129.1, 129.4, 133.4, 133.8, 136.7, 139.5, 148.0, 155.9; Mass (FAB) m/z 543 (M+H+); Anal. Calcd for C30H34N4O4Si : C, 66.39; H, 6.31; N, 10.32. Found: C, 66.11; H, 6.29; N, 10.29.
(3RS,4RS,5RS)-5-{4-[4-(1-Anthracenyl)-1H-1,2,3-triazol-1-yl]benzyloxy}-3,4-epoxy-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5m): a yellow foam; IR νmax (KBr): 2952, 2898, 2109, 1694, 1519, 1462, 1418, 1312, 1281, 1250, 1125, 1092, 1039 cm-1; 1H NMR (400 MHz, CDCl3) δ: 0.05 (9H, s), 1.02 (2H, t, J = 8.0 Hz), 3.34 (2H, brs), 3.51–3.67 (2H, m), 3.89–3.97 (3H, m), 4.20 (2H, t, J = 8.0 Hz), 4.71 (1H, d, J = 12.0 Hz), 4.87 (1H, d, J = 12.0 Hz), 7.46–7.62 (5H, m), 7.77 (1H, d, J = 6.5 Hz), 7.90 (2H, d, J = 8.0 Hz), 8.03 (2H, d, J = 8.0 Hz), 8.10 (1H, d, J = 8.0 Hz) 8.34 (1H, s), 8.52 (1H, s), 9.06 (1H, s); 13C NMR (67.8 MHz, DMSO-d6, 80 °C) δ: ‒1.9, 17.0, 41.4, 41.5, 49.3, 51.3, 62.5, 69.6, 69.8, 119.9, 121.8, 124.0, 124.4, 125.2, 125.5, 126.2, 126.3, 127.3, 127.3, 128.2, 128.4, 128.4, 128.7, 130.8, 131.3, 131.3, 135.8, 138.6, 146.4, 154.9; Mass (FAB) m/z 593 (M+H+); HRMS (FAB) calcd for C34H37N4O4Si: 593.2584. Found: 593.2584.
(3RS,4RS,5RS)-5-{4-[4-(2-Anthracenyl)-1H-1,2,3-triazol-1-yl]benzyloxy}-3,4-epoxy-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5n): a yellow solid; mp 155–156°C (toluene : n-hexane = 1 : 3); IR νmax (KBr): 2954, 1698, 1520, 1464, 1418, 1281, 1251, 1231, 1092, 1036 cm-1; 1H NMR (300 MHz, CDCl3) δ: 0.05 (9H, s), 1.02 (2H, t, J = 8.0 Hz), 3.32 (2H, brs), 3.50–3.65 (2H, m), 3.88–3.90 (3H, m), 4.20 (2H, t, J = 8.0 Hz), 4.63 (1H, d, J = 11.5 Hz), 4.82 (1H, d, J = 11.5 Hz), 7.45–7.55 (4H, m), 7.80 (1H, d, J = 7.5 Hz), 7.94–8.09 (4H, m), 8.30 (1H, s), 8.41 (1H, s), 8.46 (1H, s), 8.58 (1H, s); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.9, 17.0, 41.4, 41.5, 49.3, 51.2, 62.5, 69.6, 69.9, 119.5, 119.6, 123.3, 123.4, 125.2, 125.3, 125.7, 125.9, 126.9, 127.6, 127.6, 128.4, 128.5, 130.5, 130.8, 131.2, 131.4, 135.7, 138.6, 147.0, 154.9; Mass (FAB) m/z 593 (M+H+); HRMS (FAB) calcd for C34H37N4O4Si: 593.2584. Found: 593.2595.
(3RS,4RS,5RS)-5-{4-[4-(9-Anthracenyl)-1H-1,2,3-triazol-1-yl]benzyloxy}-3,4-epoxy-N-(2-trimethylsilyl)ethoxycarbonylpiperidine (5o): a white foam; IR νmax (KBr): 2952, 1694, 1519, 1462, 1421, 1357, 1313, 1279, 1249, 1126, 1091, 1047, 1026 cm-1; 1H NMR (270 MHz, CDCl3) δ: 0.06 (9H, s), 1.02 (2H, t, J = 8.0 Hz), 3.34 (2H, brs), 3.51–3.62 (2H, m), 3.91 (3H, brs), 4.20 (2H, t, J = 8.0 Hz), 4.69 (1H, d, J = 12.0 Hz), 4.87 (1H, d, J = 12.0 Hz), 7.42–7.52 (4H, m), 7.61 (2H, d, J = 7.5 Hz), 7.92 (2H, d, J = 8.0 Hz), 7.93 (2H, d, J = 8.0 Hz), 8.07 (2H, d, J = 7.5 Hz), 8.25 (1H, s), 8.59 (1H, s); 13C NMR (67.8 MHz, DMSO-d6, 80°C) δ: ‒1.9, 17.0, 14.4, 41.5, 49.3, 51.3, 62.5, 69.6, 69.8, 123.7, 124.1, 124.9, 125.4, 125.9, 127.7, 128.0, 128.5, 130.3, 130.6, 135.8, 138.6, 143.1, 154.9; Mass (FAB) m/z 593 (M+H+); HRMS (FAB) calcd for C34H37N4O4Si: 593.2584. Found: 593.2584.
Typical procedure of preparation of 6(3RS,4RS,5RS)-3,4-epoxy-5-[4-(1H-1,2,3-triazol-1-yl)benzyloxy]piperidine (6a): Tetra-n-butylammonium fluoride (1.0 M THF solution, 36 µmol, 36 µL) was added to 5a (10 mg, 24 µmol) and the solvent was concentrated under reduced pressure. The reaction mixture was left at rt for 2 h and purified by silica gel column chromatography (CHCl3 : MeOH = 25 : 1) to give 6a (5.3 mg, 82%) as a colorless oil. This compound was immediately dissolved in DMSO to prevent polymerization, 1H NMR (270 MHz, CDCl3) δ: 2.51 (1H, dd, J = 7.5, 13.5 Hz), 3.06 (1H, dd, J = 5.0, 13.5 Hz), 3.14–3.25 (3H, m), 3.29 (1H, d, J = 4.0 Hz), 3.65 (1H, dd, J = 5.5, 7.5 Hz), 4.69 (1H, d, J = 12.0 Hz), 4.75 (1H, d, J = 12.0 Hz), 7.53 (2H, d, J = 8.5 Hz), 7.75 (2H, dt, J = 2.0, 8.5 Hz), 7.85 (1H, d, J = 1.0 Hz), 7.99 (1H, d, J = 1.0 Hz); 13C NMR (100 MHz, CDCl3) δ: 43.9, 45.2, 50.9, 52.8, 70.6, 70.7, 120.7, 121.7, 128.9, 134.5, 136.5, 138.7.
(3RS,4RS,5RS)-3,4-epoxy-5-[4-(4-methoxymethyl-1H-1,2,3-triazol-1-yl)benzyloxy]piperidine (6b): a colorless oil; 1H NMR (270 MHz, CDCl3) δ: 2.51 (1H, dd, J = 7.5, 13.5 Hz), 3.06 (1H, dd, J = 5.5, 13.5 Hz), 3.14–3.25 (3H, m), 3.29 (1H, d, J = 3.5 Hz), 3.48 (3H, s), 3.65 (1H, dd, J = 5.5, 7.5 Hz),4.68 (2H, s), 4.67 (1H, d, J = 12.0 Hz), 4.74 (1H, d, J = 12.0 Hz), 7.52 (2H, d, J = 8.5 Hz), 7.73 (2H, d, J = 8.5 Hz), 7.98 (1H, s); 13C NMR (100 MHz, CDCl3) δ: 43.8, 45.2, 50.9, 52.8, 58.5, 66.0, 70.6, 70.7, 120.5, 120.6, 128.8, 136.5, 138.7, 145.9.
(3RS,4RS,5RS)-3,4-Epoxy-5-[4-(4-ethoxycarbonyl-1H-1,2,3-triazol-1-yl)benzyloxy]piperidine (6c): a colorless oil; 1H NMR (270 MHz, CDCl3) δ: 1.44 (3H, t, J = 7.5 Hz), 2.50 (1H, dd, J = 7.5, 13.5 Hz), 3.06 (1H, dd, J = 5.0, 13.5 Hz), 3.14–3.25 (3H, m), 3.29 (1H, d, J = 4.0 Hz), 3.65 (1H, dd, J = 5.5, 7.0 Hz), 4.47 (2H, q, J = 7.5 Hz), 4.70 (1H, d, J = 12.0 Hz), 4.75 (1H, d, J = 12.0), 7.55 (2H, d, J = 8.5 Hz), 7.76 (2H, dt, J = 2.0, 8.5 Hz), 8.50 (1H, s); 13C NMR (100 MHz, CDCl3) δ: 14.3, 43.8, 45.2, 50.9, 52.8, 61.5, 70.6, 70.7, 120.9, 125.4, 128.9, 135.8, 139.6, 140.89 160.6.
(3RS,4RS,5RS)-3,4-Epoxy-5-[4-(4-cyclopropyl-1H-1,2,3-triazol-1-yl)benzyloxy]piperidine (6d): a colorless oil; 1H NMR (270 MHz, CDCl3) δ: 0.90–1.05 (4H, m), 1.98–2.08 (1H, m), 2.50 (1H, dd, J = 7.5, 13.5 Hz), 3.05 (1H, dd, J = 5.0, 13.5 Hz), 3.10–3.21 (3H, m), 3.29 (1H, d, J = 3.5 Hz), 3.64 (1H, t, J = 6.0 Hz), 4.67 (1H, d, J = 12.0 Hz), 4.72 (1H, d, J = 12.0 Hz), 7.49 (2H, d, J = 8.5 Hz), 7.67 (1H, s), 7.71 (2H, d, J = 8.5 Hz); 13C NMR (100 MHz, CDCl3) δ: 6.7, 7.9, 43.9, 45.2, 51.0, 52.9, 70.6, 70.8, 117.8, 120.4, 128.8, 136.8, 138.3, 151.0; Mass (NALDI) m/z 413 (M+H+).
(3RS,4RS,5RS)-3,4-Epoxy-5-[4-(4-cyclohexyl-1H-1,2,3-triazol-1-yl)benzyloxy]piperidine (6e): a colorless oil; 1H NMR (270 MHz, CDCl3) δ: 1.20–1.52 (5H, m), 1.69–1.78 (3H, m), 2.08–2.11 (2H, m), 2.47 (1H, dd, J = 7.5, 13.5 Hz), 2.76–2.84 (1H, m), 3.01 (1H, dd, J = 5.0, 13.5 Hz), 3.10–3.21 (3H, m), 3.25 (1H, d, J = 4.0 Hz), 3.60 (1H, dd, J = 5.5, 7.5 Hz), 4.64 (1H, d, J = 12.0 Hz), 4.69 (1H, d, J = 12.0 Hz), 7.46 (2H, d, J = 8.5 Hz), 7.63 (1H, s), 7.75 (2H, dt, J = 2.0, 8.5 Hz); 13C NMR (100 MHz, CDCl3) δ: 26.0, 26.1, 33.0, 35.3, 43.8, 45.1, 50.9, 52.8, 70.5, 70.8, 117.4, 120.4, 128.8, 136.9, 138.2, 154.5; Mass (NALDI) m/z 355 (M+H+).
(3RS,4RS,5RS)-3,4-Epoxy-5-[4-(4-phenyl-1H-1,2,3-triazol-1-yl)benzyloxy]piperidine (6f): a white solid; mp 129–131°C (toluene : n-hexane = 2 : 1); 1H NMR (270 MHz, CDCl3) δ: 2.51 (1H, dd, J = 7.5, 13.5 Hz), 3.07 (1H, dd, J = 5.0, 13.5 Hz), 3.14-3.25 (3H, m), 3.30 (1H, d, J = 3.5 Hz), 3.65 (1H, dd, J = 5.5, 7.5 Hz), 4.70 (1H, d, J = 12.0 Hz), 4.76 (1H, d, J = 12.0 Hz), 7.37-7.56 (5H, m), 7.81 (2H, d, J = 8.5 Hz), 7.93 (2H, d, J = 8.5 Hz), 8.19 (1H, s); 13C NMR (100 MHz, CDCl3) δ: 43.8, 45.1, 50.9, 52.8, 70.6, 70.7, 117.5, 120.5, 125.8, 128.4, 128.9, 128.9, 130.1, 136.5, 138.7, 148.4.
(3RS,4RS,5RS)-3,4-Epoxy-5-[4-(4-benzyl-1H-1,2,3-triazol-1-yl)benzyloxy]piperidine (6g): a colorless oil; 1H NMR (400 MHz, CDCl3) δ: 2.43 (1H, dd, J = 7.0, 13.5 Hz), 2.97 (1H, dd, J = 4.0, 13.5 Hz), 3.04 (1H, dd, J = 2.0, 15.0 Hz), 3.08–3.10 (1H, m), 3.14 (1H, d, J = 15.0 Hz), 3.21 (1H, d, J = 4.0 Hz), 3.56 (1H, dd, J = 5.0, 7.0 Hz), 4.11 (2H, s), 4.60 (1H, d, J = 12.5 Hz), 4.64 (1H, d, J = 12.5 Hz), 7.17–7.21 (1H, m), 7.26–7.27 (4H, m), 7.41 (2H, d, J = 8.0 Hz), 7.52 (1H, s), 7.62 (2H, d, J = 8.0 Hz); 13C NMR (100 MHz, CDCl3) δ: 32.3, 43.8, 45.2, 50.9, 52.8, 70.5, 70.7, 119.5, 120.4, 126.6, 128.7, 128.7, 136.6, 138.4, 138.7, 148.5; Mass (NALDI) m/z 363 (M+H+).
(3RS,4RS,5RS)-3,4-Epoxy-5-[4-(4-phenethyl-1H-1,2,3-triazol-1-yl)benzyloxy]piperidine (6h): a colorless oil; 1H NMR (270 MHz, CDCl3) δ: 2.50 (1H, dd, J = 7.5, 13.5 Hz), 3.02–3.19 (8H, m), 3.29 (1H, d, J = 4.0 Hz), 3.63 (1H, dd, J = 5.5, 7.5 Hz), 4.67 (1H, d, J = 12.0 Hz), 4.73 (1H, d, J = 12.0 Hz), 7.19-7.33 (5H, m), 7.49 (2H, d, J = 8.5 Hz), 7.54 (1H, s), 7.68 (2H, d, J = 8.5 Hz); 13C NMR (100 MHz, CDCl3) δ: 27.5, 35.4, 43.8, 45.2, 50.9, 52.8, 70.5, 70.7, 119.1, 120.4, 126.2, 128.4, 128.5, 128.8, 136.7, 138.3, 141.0, 148.1; Mass (NALDI) m/z 377 (M+H+).
(3RS,4RS,5RS)-3,4-Epoxy-5-{4-[4-(2-pyridinyl)-1H-1,2,3-triazol-1-yl]benzyloxy}piperidine (6i): a white solid; mp 115–118°C (toluene : n-hexane = 2 : 1); 1H NMR (270 MHz, CDCl3) δ: 2.51 (1H, dd, J = 7.5, 13.5 Hz), 3.07 (1H, dd, J = 5.5, 13.5 Hz), 3.14-3.24 (3H, m), 3.30 (1H, d, J = 3.5 Hz), 3.66 (1H, dd, J = 5.5, 7.5 Hz), 4.70 (1H, d, J = 12.0 Hz), 4.75 (1H, d, J = 12.0 Hz), 7.29 (1H, dd, J = 1.0, 5.0 Hz), 7.54 (2H, d, J = 8.5 Hz),7.79–7.85 (3H, m), 8.25 (1H, dt, J = 1.0, 8.0 Hz), 8.61 (2H, m); 13C NMR (100 MHz, CDCl3) δ: 43.8, 45.2, 50.9, 52.8, 70.6, 70.7, 119.9, 120.4, 120.5, 123.1, 128.9, 136.5, 137.0, 138.8, 149.0, 149.5, 149.9; Mass (NALDI) m/z 372 (M+Na+).
(3RS,4RS,5RS)-3,4-Epoxy-5-{4-[4-(4-fluorophenyl)-1H-1,2,3-triazol-1-yl]benzyloxy}piperidine (6j): a white solid; mp 179°C (toluene : n-hexane = 2 : 1); 1H NMR (270 MHz, CDCl3) δ: 2.52 (1H, dd, J = 7.5, 13.5 Hz), 3.07 (1H, dd, J = 5.5, 13.5 Hz), 3.14-3.25 (3H, m), 3.30 (1H, d, J = 3.5 Hz), 3.65 (1H, dd, J = 5.5, 7.5 Hz), 4.70 (1H, d, J = 12.0 Hz), 4.76 (1H, d, J = 12 Hz), 7.16 (2H, t, J = 8.5 Hz), 7.55 (2H, d, J = 8.5 Hz), 7.79 (2H, d, J = 8.5 Hz), 8.89 (2H, dd, J = 5.5, 8.5 Hz), 8.15 (1H, s); 13C NMR (100 MHz, CDCl3) δ: 43.9, 45.2, 51.0, 52.8, 70.6, 70.7, 115.9 (d, J = 22.0 Hz), 117.3, 120.6, 126.4 (d, J = 3.0 Hz), 127.6 (d, J = 8.0 Hz ), 128.9, 136.5, 138.8, 147.6, 162.8 (d, J = 247.0 Hz).
(3RS,4RS,5RS)-3,4-Epoxy-5-{4-[4-(1-naphthyl)-1H-1,2,3-triazol-1-yl]benzyloxy}piperidine (6k): a yellow oil; 1H NMR (270 MHz, CDCl3) δ: 2.53 (1H, dd, J = 7.5, 13.5 Hz), 3.07 (1H, dd, J = 5.0, 13.5 Hz), 3.15-3.26 (3H, m), 3.31 (1H, d, J = 3.5 Hz), 3.67 (1H, dd, J = 5.5, 7.5 Hz), 4.72 (1H, d, J = 12.0 Hz), 4.78 (1H, d, J = 12.0 Hz), 7.52–7.65 (5H, m), 7.80 (1H, dd, J = 1.5, 7.5 Hz), 7.86 (2H, dt, J = 2.0, 8.5 Hz), 7.91–8.00 (2H, m), 8.25 (1H, s), 8.42–8.46 (1H, m); 13C NMR (100 MHz, CDCl3) δ: 43.9, 45.2, 51.0, 52.9, 70.6, 70.8, 120.5, 120.6, 125.4, 126.1, 126.8, 127.4, 127.6, 128.5, 128.9, 129.2, 131.1, 133.9, 136.6, 138.8, 147.6; Mass (NALDI) m/z 399 (M+H+).
(3RS,4RS,5RS)-3,4-Epoxy-5-{4-[4-(2-naphthyl)-1H-1,2,3-triazol-1-yl]benzyloxy}piperidine (6l): a colorless oil; 1H NMR (270 MHz, CDCl3) δ: 2.52 (1H, dd, J = 7.5, 13.5 Hz), 3.07 (1H, dd, J = 5.0, 13.5 Hz), 3.14–3.25 (3H, m), 3.31 (1H, d, J = 3.5 Hz), 3.66 (1H, dd, J = 5.5, 7.5 Hz), 4.71 (1H, d, J = 12.0 Hz), 4.76 (1H, d, J = 12.0 Hz),7.47–7.57 (4H, m), 7.81–8.03 (6H, m), 8.31 (1H, s), 8.43 (1H, s); 13C NMR (100 MHz, CDCl3) δ: 43.9, 45.2, 51.0, 52.9, 70.6, 70.7, 117.8, 120.6, 123.8, 124.7, 126.3, 126.5, 127.5, 127.8, 128.2, 128.7, 128.9, 133.3, 133.5, 136.6, 138.8, 148.5; Mass (NALDI) m/z 399 (M+H+).
(3RS,4RS,5RS)-5-{4-[4-(1-Anthracenyl)-1H-1,2,3-triazol-1-yl]benzyloxy}-3,4-epoxypiperidine (6m): a yellow oil; 1H NMR (400 MHz, CDCl3) δ: 2.55 (1H, dd, J = 7.5, 13.5 Hz), 3.09 (1H, dd, J = 5.0, 13.5 Hz), 3.14 (1H, dd, J = 1.5, 15.0 Hz), 3.18–3.19 (1H, m), 3.23 (1H, d, J = 15.0 Hz), 3.33 (1H, d, J = 3.5 Hz), 3.68 (1H, dd, J = 5.0, 7.5 Hz), 4.74 (1H, d, J = 12.0 Hz), 4.78 (1H, d, J = 12.0 Hz), 7.46–7.56 (4H, m), 7.60 (2H, d, J = 8.0 Hz), 7.77 (1H, d, J = 7.0 Hz), 7.91 (2H, d, J = 8.0 Hz), 8.02–8.04 (2H, m), 8.10 (1H, d, J = 8.0 Hz), 8.35 (1H, s), 8.52 (1H, s); 13C NMR (100 MHz, CDCl3) δ: 43.8, 45.2, 50.9, 52.8, 70.6, 70.7, 120.6, 120.6, 120.7, 124.5, 124.6, 125.6, 125.8, 126.9, 127.0, 127.8, 128.7, 128.9, 129.4, 129.6, 131.6, 131.9, 132.1, 136.6, 138.8, 147.9; Mass (NALDI) m/z 449 (M+H+).
(3RS,4RS,5RS)-5-{4-[4-(2-Anthracenyl)-1H-1,2,3-triazol-1-yl]benzyloxy}-3,4-epoxypiperidine (6n): a yellow oil; 1H NMR (400 MHz, CDCl3) δ: 2.53 (1H, dd, J = 7.0, 13.5 Hz), 3.08 (1H, dd, J = 5.0, 13.5 Hz), 3.13 (1H, dd, J = 1.5, 15.0 Hz), 3.18–3.19 (1H, m), 3.23 (1H, d, J = 15.0 Hz), 3.32 (1H, d, J = 4.0 Hz), 3.67 (1H, dd, J = 5.0, 7.0 Hz), 4.72 (1H, d, J = 12.0 Hz), 4.76 (1H, d, J = 12.0 Hz), 7.48–7.52 (2H, m), 7.57 (2H, d, J = 8.0 Hz), 7.85 (2H, d, J = 8.0 Hz), 7.97–8.04 (3H, m), 8.11 (1H, d, J = 8.0 Hz), 8.35 (1H, s), 8.45 (1H, s), 8.50 (1H, s), 8.61 (1H, s); 13C NMR (100 MHz, CDCl3) δ: 43.9, 45.2, 51.0, 52.9, 70.6, 70.8, 117.8, 120.6, 123.6, 124.7, 125.6, 125.7, 126.3, 126.7, 126.8, 128.2, 128.2, 128.9, 129.1, 131.3, 131.5, 132.0, 132.1, 136.6, 138.8, 148.5, 154.5; Mass (NALDI) m/z 449 (M+H+).
(3RS,4RS,5RS)-5-{4-[4-(9-Anthracenyl)-1H-1,2,3-triazol-1-yl]benzyloxy}-3,4-epoxypiperidine (6o): a yellow oil; 1H NMR (270 MHz, CDCl3) δ: 2.49 (1H, dd, J = 7.0, 13.5 Hz), 2.98–3.05 (2H, m), 3.10–3.14 (2H, m), 3.26 (1H, d, J = 3.5 Hz), 3.63 (1H, dd, J = 5.0, 7.0 Hz), 4.69 (2H, s), 7.34–7.45 (4H, m), 7.53 (2H, d, J = 8.0 Hz), 7.82–7.88 (4H, m), 8.00 (2H, d, J = 8.0 Hz), 8.18 (1H, s), 8.35 (1H, s), 8.51 (1H, s); 13C NMR (100 MHz, CDCl3) δ: 43.8, 45.2, 50.9, 52.8, 70.6, 70.7, 120.5, 122.6, 123.9, 125.3, 125.8, 126.2, 128.5, 128.5, 128.9, 131.3, 136.5, 138.8, 144.7; Mass (NALDI) m/z 449 (M+H+).
Examination of relaxation assay of supercoiled plasmid DNA: To a solution of supercoiled pBR 322 DNA (0.15 µg) in pH 7.0 TE buffer (9 µL) was added a DMSO solution of the compounds (1 µL, 10 µM and 100 µM), and the mixture was incubated for 24 h at 37°C. The resulting DNA analysis was conducted using electrophoresis (tris-acetate-EDTA buffer, ethidium bromide 1.3 µM solution) on 0.7% native agarose gel at 7.4 v/cm for 30 min.

ACKNOWLEDGEMENTS
This work was supported in part by a Grant-in-Aid for Science Research from the Japan Society for the Promotion of Science and the Ministry of Education, Culture, Sports, Science and Technology, Japan.

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