Home » Preclinical drugs » Preclinical characterization of substituted 6,7-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-8(5H)-one P2X7 receptor antagonists

Preclinical characterization of substituted 6,7-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-8(5H)-one P2X7 receptor antagonists

Michael K. Ameriks , et al

Janssen Pharmaceutical Research & Development L.L.C., 3210 Merryfield Row, San Diego, CA 92121, United States

doi:10.1016/j.bmcl.2015.12.052

http://www.sciencedirect.com/science/article/pii/S0960894X15303656

Scheme 3.

Synthesis of compounds 11d and 11l–t. Reagents and conditions: (a) Boc₂O, NaOH, H₂O/MeOH, 0 °C→rt (42%); (b) 2-chloro-3-trifluoromethylbenzaldehyde, Na(OAc)₃BH, DCE, rt (85%); (c) methyl chlorooxoacetate, Et₃N, CH₂Cl₂, 0 °C→rt (97%); (d) 4 N HCl/dioxane, rt, then Et₃N, CH₂Cl₂, rt (100%); (e) Et₃O⁺BF₄⁻, DCM, rt, or Lawesson’s reagent, THF, 55 °C (67–99%); (f) RCONHNH₂, 1-butanol, 130 °C (27–90%).

PATENT

US 20140275096

http://www.google.com/patents/US20140275096

Step A. tert-butyl 3-ethoxy-5,6-dihydropyrazine-1(2H)-carboxylate

To a solution of tert-butyl 3-oxopiperazine-1-carboxylate (1 g, 5 mmol) in DCM (15 mL) was added triethyloxonium tetrafluoroborate (2.9 g, 15 mmol). Stirred for 2 h and neutralized with sat. aq NaHCO₃. Layers separated and aqueous layer extracted with DCM. Combined organic layers dried over Na₂SO₄, filtered, and concentrated to give the title compound, which was used directly without further purification.

Step B. tert-butyl 3-(pyrazin-2-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazine-7(8H)-carboxylate

To a solution of tert-butyl 3-ethoxy-5,6-dihydropyrazine-1(2H)-carboxylate (1.14 g, 5 mmol) in 1-butanol (30 mL) was added pyrazine-2-carbohydrazide (685 mg, 5 mmol). The reaction mixture was heated at reflux for 16 h. After cooling to rt, the reaction mixture was concentrated and purified by chromatography (SiO2; 2.5% MeOH in DCM) to afford the desired product as a white solid (700 mg, 50% over 2 steps). MS (ESI): mass calcd. for C₁₄H₁₈N₆O₂, 302.2; m/z found, 303.2 [M+H]⁺.
1H NMR (500 MHz, CDCl3) d 9.57 (d, J=1.4 Hz, 1H), 8.62 (d, J=2.5 Hz, 1H), 8.59-8.54 (m, 1H), 4.94 (s, 2H), 4.63-4.50 (m, 2H), 3.89 (t, J=5.4 Hz, 2H), 1.51 (s, 9H).

Step C. 3-(pyrazin-2-yl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine

To a solution of tert-butyl 3-(pyrazin-2-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazine-7(8H)-carboxylate (9.3 g, 30 mmol) in DCM (100 mL) was added 1.25M HCl in EtOH (30 mL, 37.5 mmol). After 3 h, the reaction mixture was concentrated, and the resulting solid was purified by chromatography (SiO₂; 10% MeOH in DCM) to provide the desired product as a white solid (3.7 g, 61%). MS (ESI): mass calcd. for C₉H₁₀N₆, 202.1; m/z found, 203.1 [M+H]⁺. ¹H NMR (400 MHz, CD₃OD) δ 9.35 (d, J=1.4 Hz, 1H), 8.72 (dd, J=2.5, 1.6 Hz, 1H), 8.66 (d, J=2.6 Hz, 1H), 4.50 (t, J=5.6 Hz, 2H), 4.22 (s, 2H), 3.24 (t, J=5.6 Hz, 2H).

Step D. 2-(trimethylsilyl)ethyl 3-(pyrazin-2-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazine-7(8H)-carboxylate

To a solution of 3-(pyrazin-2-yl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine (1.0 g, 5.0 mmol) and N,N-diisopropylethylamine (1.7 mL, 9.9 mmol) in DMF (15 mL) was added 1-[2-(trimethylsilyl)ethoxycarbonyloxy]pyrrolidin-2,5-dione (1.5 g, 5.9 mmol). Stirred for 18 h and poured into ice cold brine (150 mL). Precipitate filtered and washed successively with water and ether to afford the desired product as a white solid (1.5 g, 89%). MS (ESI): mass calcd. for C₁₅H₂₂N₆O₂Si, 346.2; m/z found, 347.2 [M+H]⁺. ¹H NMR (500 MHz, CDCl₃) δ 9.50 (d, J=1.4 Hz, 1H), 8.56 (d, J=2.5 Hz, 1H), 8.52-8.48 (m, 1H), 4.91 (s, 2H), 4.60-4.45 (m, 2H), 4.25-4.14 (m, 2H), 3.87 (t, J=5.3 Hz, 2H), 1.07-0.92 (m, 2H), 0.01-0.04 (m, 9H).

Step E. 2-(trimethylsilyl)ethyl 8-oxo-3-(pyrazin-2-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazine-7(8H)-carboxylate

To a vigorously stirred solution of 2-(trimethylsilyl)ethyl 3-(pyrazin-2-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazine-7(8H)-carboxylate (172 mg, 0.5 mmol) in 1:1 CHCl₃:MeCN (3.8 mL) was added a solution of ruthenium (IV) oxide hydrate (9.8 mg, 0.07 mmol) and sodium metaperiodate (504 mg, 2.3 mmol) in water (4.7 mL). After 4 h, the reaction mixture was diluted with water and extracted with CHCl₃(×3). The combined organic extracts were dried (Na₂SO₄), filtered, and concentrated to afford a green oil. Purification by chromatography (SiO₂; EtOAc—10% IPA/EtOAc) provided the desired product as a white solid (663 mg, 63%).
[0140]

MS (ESI): mass calcd. for C₁₅H₂₀H₆O₃Si, 360.1; m/z found, 361.2 [M+H]⁺. ¹H NMR (500 MHz, CDCl₃) δ 9.59 (d, J=1.5 Hz, 1H), 8.63 (d, J=2.5 Hz, 1H), 8.55 (dd, J=2.5, 1.6 Hz, 1H), 4.88-4.75 (m, 2H), 4.47-4.33 (m, 2H), 4.33-4.24 (m, 2H), 1.18-1.04 (m, 2H), 0.04-(−0.02) (m, 9H).

Step F. 3-(pyrazin-2-yl)-6,7-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-8(5H)-one

To a solution of 2-(trimethylsilyl)ethyl 8-oxo-3-(pyrazin-2-yl)-5,6-dihydro-[1,2,4]triazolo[4,3-a]pyrazine-7(8H)-carboxylate (1.0 g, 2.9 mmol) in DCM (29 mL) was added TFA (5.7 mL, 75 mmol). After 1 h, the reaction mixture was concentrated. The crude residue was diluted with EtOAc, sonicated, and filtered to provide the desired product as a white solid (1.2 g, 95%). MS (ESI): mass calcd. for C₉H₈N₆O, 216.1; m/z found, 217.1 [M+H]⁺. ¹H NMR (500 MHz, DMSO-d₆) δ 9.39 (d, J=1.1 Hz, 1H), 8.77 (q, J=2.6 Hz, 2H), 8.56 (s, 1H), 4.73-4.60 (m, 2H), 3.67-3.55 (m, 2H).

Intermediate 3 was made in a manner analogous to Intermediate 1 substituting (±)-tert-butyl 2-methyl-5-oxopiperazine-1-carboxylate for tert-butyl 3-oxopiperazine-1-carboxylate in Step A. MS (ESI): mass calcd. for C₁₀H₁₀N₆O, 230.1; m/z found, 231.1 [M+H]⁺.

Intermediate 4. (6S)-1-(2-chloro-3-(trifluoromethyl)benzyl)-6-methylpiperazine-2,3-dione

[0146]

Step A. (S)-tert-butyl(2-aminopropyl)carbamate

To a solution of (S)-1,2-diaminopropane dihydrochloride (16 g, 109 mmol) in MeOH (64 mL) and water (16 mL) was added di-tert-butyl dicarbonate (28.5 g, 131 mmol) in MeOH (16 mL). The resulting solution was cooled in an ice bath, and 4N NaOH (35 mL, 140 mL) was added dropwise over 2 h. The mixture was allowed to warm to rt and stirred for a total of 20 h. The reaction was filtered, and the filtrate concentrated to remove MeOH. 200 mL EtOAc, 200 mL water, and 16 mL 1M HCl were added sequentially. The layers were separated and the aqueous layer washed with EtOAc (200 mL). The combined organic extracts were washed with 0.04M HCl (208 mL). The organic phase was separated and discarded. The aqueous phases were combined, adjusted to pH=14 with 10N NaOH (20 mL), and extracted with DCM (400 mL×2). The combined organic extracts were dried (Na₂SO₄), filtered, and concentrated to afford the desired product as a clear oil (8.0 g, 42%). MS (ESI): mass calcd. for C₈H₁₈N₂O₂, 174.1; m/z found, 175.2 [M+H]⁺. ¹H NMR (500 MHz, CDCl₃) δ 5.01 (br s, 1H), 3.24-3.09 (m, 1H), 3.09-2.95 (m, 1H), 2.92-2.84 (m, 1H), 1.45 (s, 9H), 1.35-1.19 (m, 2H), 1.07 (d, J=6.4 Hz, 3H).

Step B. (6S)-tert-butyl(2-((2-chloro-3-(trifluoromethyl)benzyl)amino)propyl) carbamate

A solution of (S)-tert-butyl(2-aminopropyl)carbamate (4.0 g, 23 mmol) and 2-chloro-3-trifluoromethylbenzaldehyde (4.8 g, 23 mmol) in DCE (100 mL) was stirred at rt for 2 h. Sodium triacetoxyborohydride (7.3 g, 34 mmol) was added at once and stirring continued overnight. Saturated aqueous NaHCO₃was added, and the resulting mixture was extracted with DCM (×2). The combined organic extracts were dried (Na₂SO₄), filtered, and concentrated to afford a clear oil. Purification by chromatography (SiO₂; hex—60% EtOAc/hex) provided the desired product as a clear oil (7.2 g, 85%). MS (ESI): mass calcd. for C₁₆H₂₂ClF₃N₂O₂, 366.1; m/z found, 367.2 [M+H]⁺. ¹H NMR (400 MHz, CDCl₃) δ 7.72-7.56 (m, 2H), 7.35 (t, J=7.7 Hz, 1H), 4.94 (s, 1H), 3.99 (d, J=14.1 Hz, 1H), 3.90 (d, J=14.1 Hz, 1H), 3.29-3.14 (m, 1H), 3.11-2.99 (m, 1H), 2.84 (dd, J=11.1, 6.2 Hz, 1H), 1.44 (s, 9H), 1.11 (d, J=6.4 Hz, 3H).

Step C. (6S)-methyl 2-((1-((tert-butoxycarbonyl)amino)propan-2-yl)(2-chloro-3-(trifluoromethyl)benzyl)amino)-2-oxoacetate

To an ice cold solution of (6S)-tert-butyl(2-((2-chloro-3-(trifluoromethyl)benzyl)amino)propyl) carbamate (7.2 g, 20 mmol) and triethylamine (2.8 mL, 21 mmol) in DCM (121 mL) was added methyl chlorooxoacetate (1.9 mL, 21 mmol) dropwise. The resulting mixture was warmed to rt and stirred overnight. After diluting with brine, the layers were separated, and the aqueous layer washed with DCM. The combined organic extracts were dried (Na₂SO₄), filtered, and concentrated to afford the desired product as a white solid (8.5 g, 97%). ¹H NMR (400 MHz, CDCl₃) δ 7.72-7.56 (m, 1H), 7.49-7.32 (m, 2H), 4.83 (d, J=17.1 Hz, 1H), 4.79-4.62 (m, 1H), 4.51 (d, J=17.1 Hz, 1H), 4.11-3.97 (m, 1H), 3.93 (s, 3H), 3.24-3.13 (m, 2H), 1.44 (s, 9H), 1.16-1.12 (m, 3H).

Step D. (6S)-methyl 2-((1-aminopropan-2-yl)(2-chloro-3-(trifluoromethyl)benzyl)amino)-2-oxoacetate hydrochloride

To a solution of 4M HCl in dioxane (75 mL) was added (6S)-methyl 2-((1-((tert-butoxycarbonyl)amino)propan-2-yl)(2-chloro-3-(trifluoromethyl)benzyl)amino)-2-oxoacetate (7.5 g, 16.7 mmol). After 30 minutes, the reaction mixture was concentrated and the product was used in the next step without further purification (6.5 g, 100%). MS (ESI): mass calcd. for C₁₄H₁₆ClF₃N₂O₃, 352.1; m/z found, 353.1 [M+H]⁺.

Step E. (6S)-1-(2-chloro-3-(trifluoromethyl)benzyl)-6-methylpiperazine-2,3-dione

To a solution of (6S)-methyl 2-((1-aminopropan-2-yl)(2-chloro-3-(trifluoromethyl)benzyl)amino)-2-oxoacetate hydrochloride (7.3 g, 18.9 mmol) in DCM (90 mL) was added triethylamine (7.9 mL, 57 mmol) at once. After 2 h, 1N HCl was added and the layers were separated. The aqueous layer was extracted with DCM (×2). The combined organic extracts were dried (Na₂SO₄), filtered, and concentrated to afford the desired product as a white solid (5.9 g, 98%). MS (ESI): mass calcd. for C₁₃H₁₁ClF₃N₂O₂, 320.1; m/z found, 321.1 [M+H]⁺. ¹H NMR (600 MHz, CDCl₃) δ 8.24 (d, J=3.6 Hz, 1H), 7.68 (dd, J=7.8, 1.1 Hz, 1H), 7.59 (d, J=7.7 Hz, 1H), 7.39 (t, J=7.8 Hz, 1H), 5.22 (d, J=15.7 Hz, 1H), 4.52 (d, J=15.7 Hz, 1H), 3.82-3.73 (m, 1H), 3.69-3.61 (m, 1H), 3.31 (ddd, J=13.2, 5.2, 2.3 Hz, 1H), 1.46-1.38 (m, 3H).
Example 14

(±)-7-[2-Chloro-3-(trifluoromethyl)benzyl]-6-methyl-3-pyrazin-2-yl-6,7-dihydro[1,2,4]triazolo[4,3-a]pyrazin-8(5H)-one………..

……………………(±) FORM

Example 14 was made in a manner analogous to Example 2 substituting Intermediate 3 for Intermediate 1 and 1-(bromomethyl)-2-chloro-3-(trifluoromethyl)benzene for 1-(bromomethyl)-2,3-dichlorobenzene to provide the desired compound as a white solid (102 mg, 63%). MS (ESI): mass calcd. for C₁₈H₁₄ClF₃N₆O, 422.1; m/z found, 423.1 [M+H]⁺. ¹H NMR (500 MHz, DMSO-d₆) 89.48 (d, J=1.2 Hz, 1H), 8.84-8.82 (m, 2H), 7.85-7.82 (m, 2H), 7.56 (t, J=7.8 Hz, 1H), 5.20 (d, J=16.5 Hz, 1H), 4.98 (dd, J=13.8, 2.2 Hz, 1H), 4.80 (dd, J=13.8, 4.6 Hz, 1H), 4.56 (d, J=16.6 Hz, 1H), 4.23-4.10 (m, 1H), 1.23 (d, J=6.7 Hz, 3H).

Example 15

(6R)-7-[2-Chloro-3-(trifluoromethyl)benzyl]-6-methyl-3-pyrazin-2-yl-6,7-dihydro[1,2,4]triazolo[4,3-a]pyrazin-8(5H)-one

Chiral SFC separation of (±)-7-[2-Chloro-3-(trifluoromethyl)benzyl]-6-methyl-3-pyrazin-2-yl-6,7-dihydro[1,2,4]triazolo[4,3-a]pyrazin-8(5H)-one on a CHIRALCEL OD-H column (5 μM, 250×20 mm) using 70% CO₂/30% MeOH provided 39 mg of the title compound as the first eluting enantiomer. [α]=+40° (c 2.2, CHCl₃).
MS (ESI): mass calcd. for C₁₈H₁₄ClF₃N₆O, 422.1; m/z found, 423.1 [M+H]⁺. ¹H NMR (500 MHz, CDCl₃) δ 9.66 (d, J=1.5 Hz, 1H), 8.68 (d, J=2.5 Hz, 1H), 8.59 (dd, J=2.5, 1.5 Hz, 1H), 7.76-7.72 (m, 1H), 7.69 (dd, J=7.9, 1.6 Hz, 1H), 7.41 (t, J=7.8 Hz, 1H), 5.44 (d, J=15.5 Hz, 1H), 5.17 (dd, J=13.9, 2.1 Hz, 1H), 4.62-4.54 (m, 2H), 4.08-4.02 (m, 1H), 1.36 (d, J=6.8 Hz, 3H).

Example 16

Chiral SFC separation of (±)-7-[2-Chloro-3-(trifluoromethyl)benzyl]-6-methyl-3-pyrazin-2-yl-6,7-dihydro[1,2,4]triazolo[4,3-a]pyrazin-8(5H)-one on a CHIRALCEL OD-H column (5 μM, 250×20 mm) using 70% CO₂/30% MeOH provided 40 mg of the title compound as the second eluting enantiomer.
[α]=−44° (c 2.2, CHCl₃).
MS (ESI): mass calcd. for C₁₈H₁₄ClF₃N₆O, 422.1; m/z found, 423.1 [M+H]⁺.
¹H NMR (500 MHz, CDCl₃) δ 9.66 (d, J=1.5 Hz, 1H), 8.68 (d, J=2.5 Hz, 1H), 8.59 (dd, J=2.5, 1.5 Hz, 1H), 7.76-7.72 (m, 1H), 7.69 (dd, J=7.9, 1.6 Hz, 1H), 7.41 (t, J=7.8 Hz, 1H), 5.44 (d, J=15.5 Hz, 1H), 5.17 (dd, J=13.9, 2.1 Hz, 1H), 4.62-4.54 (m, 2H), 4.08-4.02 (m, 1H), 1.36 (d, J=6.8 Hz, 3H).

Patent	Submitted	Granted
P2X7 MODULATORS [US2014275096]	2014-03-14	2014-09-18

see,,,,,,,,,http://worlddrugtracker.blogspot.in/2016/01/preclinical-characterization-of.html

//////////////P2X7, 6,7-Dihydro-[1,2,4]triazolo[4,3-a]pyrazin-8(5H)-one, Autoradiography, Depression, CNS, Preclinical characterization, substituted 6,7-dihydro-[1,2,4]triazolo[4,3-a]pyrazin-8(5H)-one, P2X7 receptor antagonists, Janssen Pharmaceutical Research & Development L.L.C, 1627748-32-6

FC(F)(F)c4cccc(CN1C(=O)c2nnc(n2C[C@@H]1C)c3cnccn3)c4Cl

CC1CN2C(=NN=C2C(=O)N1CC3=C(C(=CC=C3)C(F)(F)F)Cl)C4=NC=CN=C4

Tags: 1627748-32-6, 2, 3-a]pyrazin-8(5H)-one, 4]triazolo[4, 6, 7-Dihydro-[1, Autoradiography, CNS, Depression, Janssen Pharmaceutical Research & Development L.L.C, P2X7, P2X7 receptor antagonists, Preclinical characterization, substituted 6

By DR ANTHONY MELVIN CRASTO Ph.D in Preclinical drugs on January 7, 2016.

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