Efficient Synthesis of Photoreactive 2-Propoxyaniline Derivatives as Artificial Sweeteners

Abstract

5-Nitro-2-propoxyaniline is one of the strongest artificial sweeteners. However, little is known about the detailed relationship of the structure and biological activity between 5-nitro-2-propoxyaniline and its sweet receptor. Photoaffinity labeling is a useful method for revealing interactions of a small bioactive compound with molecules. Therefore, we synthesized photoreactive 2-propoxyaniline derivatives as useful tools for revealing the interactions by photoaffinity labeling.

Key words

photoaffinity labeling - chemical biology - photophore - artificial sweetener - sweet receptor

• References and Notes

• 1 Cox WS. J. Assoc. Off. Anal. Chem. 1953; 36: 749
• 2 Fitzhugh G, Nelson AA, Frawley JP. J. Am. Pharm. Assoc. 1951; 40: 583
• 3a Montmayeur J.-P, Liberles SD, Matsunami H, Buck LB. Nat. Neurosci. 2001; 4: 492
• 3b Li X, Staszewski L, Xu H, Durick K, Zoller M, Adler E. Proc. Natl. Acad. Sci. U.S.A. 2002; 99: 4692
• 4a Caldwell JE, Abildgaard F, Dzakula Z, Ming D, Hellekant G, Markley JL. Nat. Struct. Mol. Biol. 1998; 5: 427
• 4b Zell MT, Padden BE, Grant DJ. W, Schroeder SA, Wachholder KL, Prakash I, Munson EJ. Tetrahedron 2000; 56: 6603
• 4c Niccolai N, Spadaccini R, Scarselli M, Bernini A, Crescenzi O, Spiga O, Ciutti A, Maro DD, Bracci L, Dalvit C, Temussi PA. Protein Sci. 2001; 10: 1498
• 4d Offerdahl TJ, Salsbury JS, Dong Z, Grant DJ, Schroeder SA, Prakash I, Gorman EM, Barich DH, Munson EJ. J. Pharm. Sci. 2005; 94: 2591
• 4e Assadi-Porter M, Tonelli M, Maillet E, Hallenga K, Benard O, Max M, Markley JL. J. Am. Chem. Soc. 2008; 130: 7212
• 5a Hatada M, Jancarik J, Graves B, Kim SH. J. Am. Chem. Soc. 1985; 107: 4279
• 5b Feinstein RD, Polinsky A, Douglas AJ, Beijer CM. G. F, Chadha RK, Benedetti E, Goodman M. J. Am. Chem. Soc. 1991; 113: 3467
• 6a Bassoli A, Drew MG. B, Merlini L, Morini G. J. Med. Chem. 2002; 45: 4402
• 6b Morini G, Bassoli A, Temussi PA. J. Med. Chem. 2005; 48: 5520
• 7a Masuda K, Koizumi A, Misaka T, Hatanaka Y, Abe K, Tanaka T, Ishiguro M, Hashimoto M. Bioorg. Med. Chem. Lett. 2010; 20: 1081
• 7b Tsunekawa Y, Masuda K, Muto M, Muto Y, Murai Y, Hashidoko Y, Orikasa Y, Oda Y, Hatanaka Y, Hashimoto M. Heterocycles 2012; 84: 283
• 7c Sakurai M, Masuda K, Wang L, Murai Y, Sakihama Y, Hashidoko Y, Hatanaka Y, Hashimoto M. Heterocycles 2014; 88: 629
• 7d Sakurai M, Yoshida T, Wang L, Murai Y, Masuda K, Sakihama Y, Hashidoko Y, Hatanaka Y, Hashimoto M. Heterocycles 2015; 90: 698
• 7e Wang L, Yoshida T, Muto Y, Murai Y, Tachrim ZP, Ishida A, Nakagawa S, Sakihama Y, Hashidoko Y, Masuda K, Hatanaka Y, Hashimoto M. Eur. J. Org. Chem. 2015; 3129
• 8 Iwamura H. J. Med. Chem. 1980; 23: 308
• 9 Hashimoto M, Hatanaka Y. Eur. J. Org. Chem. 2008; 2513
• 10 Clewley RG, Fischer A, Henderson GN. Can. J. Chem. 1989; 67: 1472
• 11 Andersen J, Madsen U, Bjorkling F, Liang X. Synlett 2005; 2209
• 12 5-Azido-2-propoxyaniline (6) Compound 5 (57.3 mg, 0.25 mmol), NaN₃ (32.3 mg, 0.5 mmol), CuI (4.74 mg, 24.9 μmol), l-proline (8.6 mg, 75 μmol), and NaOH (3 mg, 75 μmol) were dissolved in 70% EtOH (500 μL). The reaction mixture was stirred for 1 d at 95 °C, and the solution was removed. The residue was purified by silica column chromatography (CHCl₃–n-hexane, 1:1; then EtOAc–n-hexane, 1:3) to yield 6 (20.2 mg, 42%) as brown oil. ¹H NMR (500 MHz, CDCl₃): δ = 6.72 (d, J = 8.1 Hz, 1 H), 6.39–6.34 (m, 2 H), 3.93 (t, J = 6.6 Hz, 2 H), 3.90 (br s, 2 H), 1.87–1.77 (m, J = 7.1 Hz, 2 H), 1.04 (t, J = 7.4 Hz, 3 H). ¹³C NMR (126 MHz, CDCl₃): δ = 144.1, 137.7, 132.6, 112.3, 108.2, 105.4, 70.2, 22.6, 10.6. ESI-HRMS: m/z [M + H]⁺ calcd for C₉H₁₃BrN₄O: 193.1089; found: 193.1090.
• 13 Cao X, Deng X.-Q, Shu B, Wang S.-B, Quan Z.-S. Drug Res. 2013; 63: 319
• 14 Brain C.-T, Culshaw A.-J, Dziadulewicz E.-K, Schopfer U. WO 2002042248, 2002
• 15 (3-Amino-4-propoxyphenyl)(phenyl)methanone (10) N-(5-Benzoyl-2-propoxyphenyl)acetamide (9, 100 mg, 0.34 mmol) was dissolved in MeOH (2 mL) and concd HCl (2 mL). The mixture reacted for 1 h under reflux. The solution was concentrated, and sat. NaHCO₃ was added to the residue. The desired product was extracted with EtOAc (2 × 50 mL), dried over MgSO₄, and then evaporated. The residue was purified by silica column chromatography (EtOAc–n-hexane, 1:4) to yield 10 (81.0 mg, 94%) as yellow oil. ¹H NMR (270 MHz, CDCl₃): δ = 7.81–7.68 (m, 2 H), 7.62–7.38 (m, 3 H), 7.27 (s, 1 H), 7.19 (d, J = 8.4 Hz, 1 H), 6.79 (d, J = 8.2 Hz, 1 H), 4.04 (t, J = 6.4 Hz, 2 H), 3.93 (br s, 2 H), 1.87 (sext, J = 7.1 Hz, 2 H), 1.07 (t, J = 7.4 Hz, 3 H). ¹³C NMR (68 MHz, CDCl₃): δ = 196.2, 150.6, 138.7, 136.3, 131.7, 130.3, 129.8, 128.1, 122.7, 116.0, 109.9, 69.9, 22.4, 10.4. ESI-HRMS: m/z [M + H]⁺ calcd for C₁₆H₁₈NO₂: 256.1338; found: 256.1341.
• 16 Lu X, Cseh S, Byun H-S, Tigyi G, Bittman R. J. Org. Chem. 2003; 68: 7046
• 17 Kitamura C, Naito T, Yoneda A, Kobayashi T, Naito H, Komatsu T. Chem. Lett. 2009; 38: 600
• 18 Chatterjee A, Oh DJ, Kim KM, Youk K.-S, Ahn KH. Chem. Asian J. 2008; 3: 1962
• 19 Linderman RJ, Graves DM. J. Org. Chem. 1989; 54: 661
• 20 Murai Y, Masuda K, Sakihama Y, Hashidoko Y, Hatanaka Y, Hashimoto M. J. Org. Chem. 2012; 77: 1092
• 21 Kosemura S, Emori H, Yamamura S, Anai T, Tomita K, Hasegawa K. Tetrahedron Lett. 1997; 38: 2125
• 22 2-Propoxy-5-[3-(trifluoromethyl)-3H-diazirin-3-yl]aniline (22) Diaziridine 21 (38.1 mg, 0.15 mmol) and activated MnO₂ (excess) were suspended in Et₂O (6 mL). The reaction mixture was stirred at r.t. for 1 h, then filtered insoluble material. The filtrate was concentrated, and the residue was purified by silica column chromatography (CH₂Cl₂–n-hexane, 1:3) to yield 22 (35.5 mg, 94%) as yellow oil. ¹H NMR (500 MHz, CDCl₃): δ = 6.72 (d, J = 8.6 Hz, 1 H), 6.55 (s, 1 H), 6.46 (d, J = 8.6 Hz, 1 H), 3.94 (t, J = 6.6 Hz, 2 H), 3.90 (br s, 2 H), 1.86–1.78 (m, 2 H), 1.03 (t, J = 7.4 Hz, 3 H). ¹³C NMR (126 MHz, CDCl₃): δ = 147.6, 136.8, 122.4 (q, ¹J _CF = 274.7 Hz), 121.4, 116.9, 112.5, 111.1, 69.9, 28.4 (q, ²J _CF = 40.8 Hz), 22.6, 10.6. ¹⁹F NMR (471 MHz, CDCl₃): δ = –65.2. ESI-HRMS: m/z [M + H]⁺ calcd for C₁₁H₁₃F₃N₃O: 260.1011; found: 260.1010.
• 23 Cellular Responses with Cell-Based Assay The hT1R2-hT1R3 and G16-gust44 cell lines (approx 80,000 cells) were treated in 96-well black-wall plates with a calcium indicator dye (FLIPR Calcium 4) for 1 h at 37 °C. Fluorescence changes by excitation at λ = 485 nm, emission at λ = 525 nm, were monitored at 2 s intervals. The photoreactive compounds (6, 10, 22) and sucrose (as positive control) were added at 20 s, and scanning was continued for an additional 4 min.
• 24 Imada T, Misaka T, Fujiwara S, Okada S, Fukuda Y, Abe K. Biochem. Biophys. Res. Commun. 2010; 397: 220