ASAHI GLASS CO., LTD : Research & Development/R&D Library/Vol.52/Paper 5

Paper5. Synthesis of a Novel Trifluorome than esulfonamidophenyl
-substituted Quinoline Derivative, GA 0113,
and its Pharmacological Profiles

Yoshitomi Morizawa*, Takashi Okazoe**, Shu-zhong Wang** and Jun Sasaki***

　The trifluoromethanesulfonamidophenyl substituted quinoline GA 0113 has been
synthesized from o - nitrobenzoyl chloride via a multi - step process. GA 0113 displaced specific binding of [ ¹²⁵ I] - Sar1, Ile⁸ - Ang II to AT1 receptors in membrane from Sf9 cells. In conscious normotensive dogs, GA 0113 inhibited the Ang II - induced pressor response with ID50 of 0.032 mg/kg and dose - dependently increased plasma renin activity for 48 h.

*Chiba Factory **Research Center ***Chemical Company


目次
	1. Introduction
	2. Results and Discussion
	3. Conclusion
	4. Experimental

1. Introduction

　The renin - angiotensin system (RAS)is well known to play an important role in blood pressure regulation and electrolyte homeostasis, and has the octapeptide angiotensin II (AII)as its principal active hormone^（1）. The prevention of the formation of AII from angiotensin I (AI)by angiotensin - converting enzyme (ACE)inhibitors induces blockade of the RAS in antihypertensive therapy. However, the lack of specificity of ACE inhibitors, having the adverse effects such as dry cough and angioedema, provided a major reason for developing alternative therapy.
　Although saralasin (Sar¹ - Ala⁸ - Ang II)was the first specific peptide antagonist of AII and used as pharmacological tools, the peptide has limited therapeutic value of the poor oral bioavailability and short duration of action. Many pharmaceutical industries have focused on finding a more specific way to block the RAS. Among them, nonpeptide AII antagonists were an attractive means, lacking the disadvantages of the peptide AII receptor antagonists. Most of them contain a nitrogen heterocycle linked to a biphenyltetrazole by a methylene spacer, as in losartan (Dup - 753)^（2） and candesartan cilexetil (TCV - 116)^（3） .
　There are some reports on the introduction of perfluoroalkyl substituents in nonpeptide AII receptor antagonists capitalizing on the enhanced binding affinity^（4） . On the other hand, much attention has been paid to the replacement of aryltetrazole group as a means for improving the relatively low oral bioavailability. AII antagonists incorporating squaric acid, acylsulfonamides, trifluoromethanesulfonamide (triflamide)^（5） , and acidic heterocycle moieties have recently been reported. Our strategy was to find a novel biphenyltetrazole replacement, and we describe herein the synthesis and pharmacological activity of the new potent nonpeptide nontetrazole AII receptor antagonist, designated GA0113, which carries a triflamide group as a more lipophilic acidic group and a quinoline moiety.

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2. Results and Discussion

2 . 1 Synthesis of GA 0113
　The key intermediate caroboxyphenyl substituted quinoline 3 was synthesized by the reaction of 5 - methylisatin (1)with 2 - acetylbenzoic acid followed by selective decarboxylation of the dicarboxylic acid thus produced (2) in the presence of catalytic amount of H2SO4 in quinoline (Scheme 1). After methyl esterification and benzylic bromination, an N - alkylation reaction with imidazopyridine derivative (4) followed by hydrolysis gave the carboxyphenyl - substituted quinoline GA 0056, which possessed antihypertensive activity. Curtius rearrangement methodology was then employed [ using (PhO)2P(O)N3 －Et3N －t - BuOH] to convert the carboxyl group to amino (CO2H →CON3 → N=C=O →NCO2Bu^t →NH2);however, the aniline derivative was obtained only in low yield (5%based on GA 0056), even after improving the reaction conditions. Finally, the quinolinylaniline was transformed into the desired triflamide GA 0113,6 - {(2 - ethyl - 5,7 - dimethyl - 3 H - imidazo [ 4,5 - b] pyridin - 3 - yl)methyl} - 2 - [ 2 - (trifluoromethanesulfonamido) phenyl] quinoline, by treatment with (CF3SO2)2O.
　After several attempts to develop a satisfactory synthetic method for producing bulk quantities of the quinolinylaniline precursor of GA 0113, for example, unsuccessfully to achieve decarboxylation of the nitrophenyl analogue of compound 2 or a modified Skraup reaction with 4 - methylaniline and 3 - (2 - nitrophenyl)acrolein, we have found a practical process through the application of Conrad - Limpach ’s method (Scheme 2)
　The key 2 - nitrophenyl ketone 6 was synthesized from 2 - nitrobenzoyl chloride (5)and diethyl malonate in the presence of magnesium ethoxide, and successive decarboxylation. Ring construction was accomplished by the reaction of 6 with p - toluidine, followed by treatment of 7 with polyphosphoric acid, then phosphorous oxychloride to give nitrophenylquinoline 8 in a fairly good yield. After N - alkylation according to the transformation of 3 to GA0056 (Scheme 1), chloro nitro compound 9 was reduced and the resulting aniline converted to GA0113. The overall yield of GA 0113 from 5 was 10%in a large scale production.

2 . 2 Biological Data
　Pharmacological profiles of GA 0113 are as follows ⁽⁶⁾ . A binding assay for AT1 and AT2 receptors was performed using commercially - available membrane fractions expressing either human AT1 or AT2. GA 0113 and CV - 11974 (an AT1 antagonist and a metabolite of TCV - 116) displaced the specific binding of [ ¹²⁵ I] - Sar¹ , Ile⁸ - Ang II to binding sites in AT1 in a concentration - dependent manner (Figure 1), and the IC50 values were 1.1 ×10^{- 8} and 1.3 ×10^-7 mol/L, respectively. In contrast, specific binding of [ ¹²⁵ I] - Sar¹ , Ile⁸ - Ang II to binding sites in AT2 was displaced by PD 123319, a selective AT2 antagonist, but not by GA 0113.
　Antihypertensive effects in renal artery ligated hypertensive rats (RALHR)was examined with male Wister rats. Administration of GA 0113 (0.01 - 1 mg/kg)reduced systolic blood pressure (SBP)in a dose - related manner with ED25 of 0.015 mg/kg, and at dose 0.1 mg/kg or more, SBP was reduced for more than 24 h without affecting heart rate (HR)significantly (Figure 2). Pharmacokinetic examination revealed that GA0113 has longer T1/2 (12.2 h)and much better bioavailability (BA) (94%), whereas the T1/2 and BA of TCV - 116 have been reported to be 3.8 h and 19 - 28%, respectively^（7） . The high BA might attribute to the replacement of the tetrazole group with the more lipophilic and metabolically more stable acidic isostere, triflamide group, taking into consideration that the pKa (5 to 6)of aryltetrazole is similar to that (4.45)of PhNHSO2CF3⁽⁸⁾ , and a unique quinolinyl group.

2 . 3 MOPAC Calculation
　MOPAC PM3 calculation of anions PhNSO2R (R =CH3, CH2F, CHF2, CF3)in water (ε=78.4)using COSMO method optimized by EF indicated that the bond - lengths of N - S increase gradually from 1.75 (CH3)to 2.02 Å(CF3)and the dipole moments of their anion are dramatically decreased from 14.3 (CH3)to 9.7 D (CF3). Moreover, we have found that AM1 Hamiltonian is not suitable for such anions because the C - N - S bond angle increased from 154.2^o(CH3)to 176.0 ^o (CF3).

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3. Conclusion

　Although GA 0113 is not structurally related to TCV - 116 and other AT1 receptor antagonists bearing a biphenyltetrazole moiety, it may become a potent agent for the treatment of hypertension and other Angiotensin II - related cardiovascular diseases.

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4. Experimental

N - (4 ’- methylphneyl) - 3 - (4 ’- methylanilino) - 3 - (nitrophenyl) acrylamide (7)
　To a suspension of 125 mL of ethanol containing 70.5 g (615 mmol)of magnesium ethylate, 96.0 g (600 mmol)of diethyl malonate in 250mL of toluene was added dropwise. After stirring at a bath temperature of 70 °C for 2 hours, the reaction mixture was cooled to 0 °C, and 105 g (565 mmol)of 2 - nitrobenzoyl chloride in 625 mL of toluene was added dropwise. After stirring at room temperature for 3 hours, 60 mL of sulfuric acid in 250 mL of water was added and the whole was poured into 350 mL of water. The organic layer was washed with 350 mL of saturated aqueous sodium chloride solution and dried over magnesium sulfate. After filtration and concentration, the resulting residue was dried in vacuo to give 187.5 g of crude diethyl 2 - (nitrobenzoyl)malonate.
　To 187.5 g of the above compound, 250 mL of water and 262 mL (1.375 mmol)of p - toluenesulfonic acid monohydrate were added. The reaction mixture was heated to reflux for 2.5 hours and then cooled to room temperature. The organic layer extracted with chloroform (250 mL)was washed with 250 mL of 7%aqueous solution of sodium hydrogencarbonate and successively 250 mL of saturated aqueous sodium chloride solution. After drying over magnesium sulfate, the resulting residue was filtrated, concentrated, and dried in vacuo to give 138.5 g of crude product of ethyl 2 - nitrobenzoylacetate 6 .
　To the above product 6, 377 mL of toluene, 121 g (1.13 mmol)of p - toluidine and 1.6 g (11.3 mmol)of p - toluidine hydrochloride were added. The reaction mixture was heated under reflux for 8.5 hours using a Dean - Stark trap. During the refluxing, about 39 mL of water containing ethanol was distilled off. After further distilling off 282 mL of toluene, the mixture was cooled to 0 °C, and 100 mL of 5%aqueous potassium hydroxide solution dissolved in ethanol/water (9/1)was added. The resulting mixture was stirred at room temperature for 10 minutes, and the crystals precipitated were collected by filtration.
　The obtained filtration residue was washed successively with 50 mL of 5%potassium hydroxide solution dissolved in ethanol/water (9/1) twice and 50 mL of ethanol/water (9/1)twice and then dried in vacuo to give 145.5 g of N - (4 ’- methylphenyl) - 3 - (4 ’- methylanilino) - 3 - (nitrophenyl) acrylamide 7 (66.5%yield).
　¹H NMR (400 MHz, CDCl3)δ2.19 (s, 3H), 2.31 (s, 1H), 4.66 (s, 1H), 6.63 - 7.88 (m, 13H), 11.4 (s, 1H).

　4 - chloro - 6 - methyl - 2 - (2 - nitrophenyl) - 4 - quinoline (8)
　To 727.5 g of polyphosphoric acid, 145.5 g of 7sup was added. The mixture was stirred at from 100sup to 115 °C for 5 hours and then poured into 1455g ofsup ice - water. After allowed to stand overnight, thesup solid was collected by decantation. The solid wassup broken finely in water added and filtrated. Thesup resulting filtration residue was washed with 500sup mL of water twice and dried under reducedsup pressure at 60 °C. Then 500 mL of methanol wassup added to the solid and stirred for 2 hours. Thesup solid collected by filtration was washed with 250sup mL of methanol twice and dried under reducedsup pressure at 40 °C to give 53.3 g (50.6%yield)of 6 - sup methyl - 2 - (2 - nitrophenyl) - 4 - quinolone. Furthermore, sup 17.4 g (16.5%yield)of the product was obtainedsup from the filtrate.
　¹H NMR (400 MHz, DMSO - d6)δ2.43 (s, 3H), 6.00 (br s, 1H), 7.41 - 7.56 (m, 2H), 7.75 - 7.95 (m, 4H), 8.20 - 8.28 (m, 1H).
　To 63.9 mL of phosphorous oxychloride, 53.3 g of 6 - methyl - 2 - (2 - nitrophenyl) - 4 - quinolone obtained above was added and the mixture was heated to 110 °C for 4 hours. Then the mixture was poured into 640 mL of ice - water, and 1600 mL of chloroform wad added under stirring, followed by neutralization with 10 N aqueous sodium hydroxide solution. The resulting organic layer was washed with 640 mL of water, concentrated, and dried in an evaporater to obtain 55.0 g of crude product of 4 - chloro - 6 - methyl - 2 - (2 - nitrophenyl) - 4 - quinoline. To a 38.06 g of portion of the above product taken was added 380 mL of methanol. The resulting mixture was suspended and filtered. The resulting filtration residue was washed with 190 mL of methanol twice and dried under reduced pressure to give 29.5 g of 4 - chloro - 6 - methyl - 2 - (2 - nitrophenyl) - 4 - quinoline. Furthermore, 5.00 g of the crude product was recrystallized from ethyl acetate to give 3.26 g of the desired compound 8 (totally 60.8% yield).
　¹H NMR (400 MHz, CDCl3)δ2.61 (s, 3H), 7.58 - 7.72 (m, 5H), 7.98 - 8.03 (m, 3H).

　4 - chloro - 6 - [ (2 - ethyl - 5, 7 - dimethyl - 3H - imidazo[ 4, 5 - b] piridin - 3 - yl)methyl] - 2 - (nitrophenyl)quinoline (9)
　To 4 - chloro - 6 - methyl - 2 - (2 - nitrophenyl) - 4 - quinoline 8 (27.6 g, 92.4 mmol)in chloroform (110 mL), 15.6 g of N - bromosuccinimide (NBS)(87.8 mmol)was added with stiring. Then, 2, 2 ’ - azobis (2, 4 - dimethyl - valeronitorile) (0.78 g)in chloroform (15 mL)was added dropwise. The whole was heated to reflux for 1 hour. After cooling to room temperature, the mixture was poured into 220 mL of water and sep - arated. The organic layer was washed with 110 mL of water twice. Concentration and recrystallization from toluene to give 14.7 g (44.3%yield based on NBS)of 4 - chloro - 6 - bromemethyl - 2 - (2 - nitrophenyl) - 4 - quinoline.
　H NMR (400 MHz, CDCl 3)δ4.71 (s, 2H), 7.60 - 7.84(m, 5H), 8.02 (d, J =8.0 Hz, 1H), 8.09 (d, J =8.8 Hz, 1H), 8.25 (s, 1H).
　To the solution of 2 - ethyl - 5, 7 - dimethyl - 1 H - imidazo[ 4, 5 - b] pyridine (7.45 g, 42.5 mmol)in N, N - dimethylformamide (DMF)(61 mL), sodium hydride (60%, 1.79 g, 44.6 mmol)was added and stired at room temperature for 30 minutes.　Then, 15.3 g of 4 - chloro - 6 - bromomethyl - 2 - (2 - nitrophenyl) - 4 - quinoline was added and reacted at same temperature for 12 hours.　After adding 120 mL of toluene, the whole was poured into a mixture of toluene (60 mL)and water (300 mL).　After addition of ethyl acetate (120 mL), the mixture was separated and the aqueous layer was extracted with a mixture of toluene (90mL)and ethyl acetate (90 mL).　The combined organic layer was evaporated and the resulting residue in toluene (90 mL)added was washed with 90 mL of water twice.　The resulting insolubles were filtered off and the organic layer was concentrated in an evaporator, followed by allowed to stand at 5 °C. The crystals precipitated were collected, washed with 10 mL of toluene twice, and dried to afford the desired compound 9 (8.12 g, 40.5%yield).
　¹H NMR (400 MHz, CDCl3)δ1.36 (t, J =7.6 Hz, 3H), 2.61 (s, 3H), 2.66 (s, 3H), 2.84 (q, J =7.6 Hz, 2H), 5.69 (s, 2H),6.93 (s, 1H), 7.53 - 7.72 (m, 5H), 8.01 (d, J = 8.0 Hz, 2H), 8.08 (s, 1H).

　6 - {(2 - ethyl - 5, 7 - dimethyl - 3H - imidazo[ 4, 5 - b] pyridin - 3 - yl) methyl} - 2 - [ 2 - (trifluoromethanesulfonamido)phenyl] quinoline, GA 0113
　To potassium hydroxide (8.0 g)in methanol (240 mL), 9 (8.12 g, 17.2 mmol)and 5%palladium - carbon (0.80 g)were added. The whole was stirred under a hydrogen atmosphere for 17 hours. After adding 120 mL of chloroform, the reaction mixture was filtered on Celite. To the resulting filtrate, water (120 mL)was added. The organic layer separated was washed with water (120 mL). Water (60 mL) was added again and a 130 mL portion was distilled off by heating under an atmospheric pressure. After allowed to stand at 5 °C, the crystals precipitated were collected by filtration. The crystals were further recrystallized from a mixture of chloroform with methanol to obtain 2 - {6 - [ (2 - ethyl - 5, 7 - dimethyl - 3H - imidazo[ 4, 5 - b] pyridin - 3 - yl)methyl] quinolin - 2 - yl}aniline (3.30 g, 47.1%yield).
　¹H NMR (400 MHz,CDCl3)δ1.31 (t,J =7.6 Hz, 3H),2.61 (s,3H),2.67 (s,3H),2.81 (q,J =7.6 Hz,2H), 5.64 (s,2H),6.15 (br s,2H),6.80 (t,J =8.0 Hz,2H), 6.93 (s,1H),7.20 (dd,J =7.0,1.2 Hz,1H),7.41 (s,1H), 7.51 (dd,J =2.0,8.8 Hz,1H),7.66 (d,J =7.6 Hz,1H), 7.80 (d,J =8.8 Hz,1H),5H),7.97 (d,J =8.8 Hz,1H), 8.06 (d,J =8.8 Hz,1H).
　Trifluoromethanesulfonic anhydride (3.6 mL, 21.4 mmol)in chloroform (36 mL)was added dropwise into the solution of the above compound (8.73 g, 21.4 mmol)and triethylamine (6.0 mL, 42.8 mmol)in chloroform (87 mL)over 50 minutes under cooling in ice - bath. After stirring for 10 minutes, 2M acetic acid (123 mL)was added dropwise into the mixture under ice - cooling. The resulting mixture was separated and the organic layer was washed successively with deionized water (123 mL)twice, 2%aqueous sodium bicarbonate (123 mL)once to afford crude desired compound in chloroform.
　The chloroform solution of the above compound in ethanol (60 mL)was heated to a bath temperature of 90 - 115 °C. After distilling off 176 mL of the solvent, the residue was allowed to stand at 0 °C overnight and the crystals precipitated were collected by filtration. After washing with ethanol (10 mL)three times, the crystals were dried under reduced pressure.　An 8.36 g portion of the obtained crystals (8.48 g in total)was taken up and ethyl acetate (425 mL)and ethanol (175 mL)were added. After distilling off 325 mL of the solvent, the residue was allowed to stand at room temperature. The crystals thus precipitated were collected by filtration, washed with ethanol (10 mL)three times and dried under reduced pressure to give 6.35 g (55.0%yield)of crystals, GA113;mp 252.0 °C.
　¹H NMR (400 MHz, CDCl3)δ1.34 (t, J =7.6 Hz, 3H), 2.60 (s, 3H), 2.67 (s, 3H), 2.82 (q, J =7.6 Hz, 2H), 5.67 (s, 2H), 6.94 (s, 1H), 7.29 (t, J =8.0 Hz, 2H), 7.43 (s, 1H), 7.48 (t, J =7.2 Hz, 1H), 7.69 (dd, J =8.6, 1.4 Hz, 1H), 7.84 (d, J =8.0 Hz, 1H), 7.99 - 8.05 (m, 3H), 8.22 (d, J =9.2 Hz, 1H). ¹⁹F NMR (400 MHz, CDCl3) δ－77.183.

－Acknowledgement －
We thank Drs. Hajime Ebisu, Masakuni Nishikawa, and Hiroshi Shinyama, Pharmaceutical Research Division, WelFide Corporation, when the study was done, for evaluation of pharmacological profiles, and Dr. Yoshihisa Inoue, Drug Discovery Laboratories, Pharmaceutical Research division, WelFide Corporation, when the study was done, for the MOPAC calculations and discussion.

－References －

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