AN 3485

AN3485,

6-(4-(aminomethyl)-2-chlorophenoxyl)benzo[c][1,2]oxaborol-1(3H)-ol,
was synthesized at Anacor Pharmaceuticals as described in patent application WO 2010028005
A1

6-[4-(Aminomethyl)-2-chlorophenoxy]-2,1-benzoxaborol-1(3H)-ol hydrochloride

Anacor Pharmaceuticals, Inc.

http://jpet.aspetjournals.org/content/early/2012/11/28/jpet.112.200030.full.pdf

Pro-inflammatory cytokines play a critical role in the development of autoimmune and
inflammatory diseases. Targeting the cytokine environment has proven efficient for averting
inflammation. In this study, we reported that 6-(4-(aminomethyl)-2-
chlorophenoxyl)benzo[c][1,2]oxaborol-1(3H)-ol (AN3485), a benzoxaborole analog, inhibited
TLR2-, TLR3-, TLR4- and TLR5-mediated TNF-α, IL-1β and IL-6 release from human PBMCs
and isolated monocytes with IC50s ranging from 18 to 580 nM, and the inhibition was mediated
at the transcriptional level. Topical administration of AN3485 significantly reduced PMAinduced contact dermatitis and oxazolone-induced delayed-type hypersensitivity in mice,
indicating its capability of penetrating skin and potential topical application in skin
inflammation. Oral administration of AN3485 showed dose-dependent suppression of LPSinduced TNF-α and IL-6 production in mice with an ED90 of 30 mg/kg. Oral AN3485, 35
mg/kg, twice a day, suppressed collagen-induced arthritis in mice over a 20-day period. The
potent anti-inflammatory activity in in vitro and in vivo disease models makes AN3485 an
attractive therapeutic lead for a variety of cutaneous and systemic inflammatory diseases

A new class of boron-containing small molecules has been developed over the past several
years as potential drugs. Different from carbon, boron contains an electrophilic empty p-orbital
which can form transient bonds with nucleophiles in an enzyme active site, which mimics a
tetrahedral transition state of peptide bond cleavage in an enzymatic reaction (Baker et al., 2011).
The benzoxaboroles, in which the boron atom is incorporated into a heteroaromatic ring system,
are able to inhibit a number of important enzymes, including bacterial and fungi Leucyl-tRNA
synthetase (Rock et al., 2007), human phosphodiesterase-4 (PDE4) (Akama et al., 2009) and
HCV NS3/4A protease (Li et al., 2010). Three benzoxaboroles, AN2690 (Tavaborole), AN2728
and AN3365 (GSK’052) are in clinical trials for treatment of onychomycosis, psoriasis/atopic dermatitis and Gram-negative bacterial infection, and have been proven safe in human when
applied topically or systemically

……………………………………………………….

Structure-activity relationships of 6-(aminomethylphenoxy)-benzoxaborole derivatives as anti-inflammatory agent
Bioorg Med Chem Lett 2013, 23(6): 1680

http://www.sciencedirect.com/science/article/pii/S0960894X13001054

Scheme 2.

Synthesis of compounds 9a–e. Reagents and conditions: (a) K₂CO₃, DMSO, 80–90 °C, overnight (33–61%); (b) LAH, THF, 0 °C to rt, 1 h, then 4 M HCl in 1,4-dioxane (43–68%); (c) aq NaOH, MeOH, 50 °C, 2 h (61%), (d) Ac₂O, pyridine, rt (79%).

Synthesis of 6-(4-(aminomethyl)-2-chlorophenoxy)benzo[c][1,2]oxaborol-1(3H)-ol (9e): To a solution of 3H-benzo[c][1,2]oxaborole-1,6-diol (8) (300 mg, 2.00 mmol) in DMSO (30 mL) were added K₂CO₃(828 mg, 6.00 mmol) and 3-chloro-4-fluoro-benzonitrile (7b) (933 mg, 6.00 mmol). The reaction was heated at 90 °C for 7 h. After cooling the reaction mixture to room temperature, EtOAc (50 mL) was added. The organic layer was washed with water (5 × 50 mL). The organic layer was evaporated under vacuum. The residue was purified by reverse phase chromatography to afford 3-chloro-4-(1-hydroxy-1,3-dihydro-benzo[c][1,2]oxaborol-6-yloxy)-benzonitrile (9b) (190 mg, 33%). ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.24 (s, 1H), 8.22 (s, 1H), 7.77 (d, J = 7.8 Hz, 1H), 7.50 (d, J = 8.2 Hz, 1H), 7.34 (s, 1H), 7.28 (d, J = 8.2 Hz, 1H), 7.01 (d, J = 8.6 Hz, 1H), 4.99 (s, 2H); ESIMS (m/z): 284 (M−H)⁻; HPLC: 96.4% (220 nm), 96.0% (maxplot).
To a solution of compound 9b (136 mg, 0.480 mmol) in anhydrous THF (60 mL) was added lithium aluminum hydride (1 M/ether, 1.19 mL, 1.19 mmol) at 0 °C. The reaction was stirred for 2 h. Then the reaction was quenched with 1 M HCl (30 mL). MeOH (50 mL) was added and the solution was filtered. The filtrate was evaporated under vacuum. The residue was purified by reverse phase chromatography (biotage, gradient MeOH/H₂O from 10% to 100%). To a suspension of 9e free base in MeOH (5 mL) was added 4 M HCl in 1,4-dioxane (0.2 mL). The mixture became a clear solution then precipitates formed, which were collected by filtration to afford 9e (106 mg, 68%) as a white solid. ¹H NMR (400 MHz, DMSO-d₆) δ ppm 9.19 (s, 1H), 8.18 (br s, 3H), 7.75 (s, 1H), 7.44–7.39 (m, 2H), 7.19–7.10 (m, 3H), 4.98 (s, 2H), 4.03 (q, J = 5.5 Hz, 2H); ESIMS (m/z): 290 (M+H)⁺; HPLC: 95.9% (220 nm), 96.9% (maxplot).

…………………………………………………………

Patent

https://www.google.com/patents/WO2010028005A1?cl=en

(X) IS AN 3485

Compound 2:

To a solution of 2-hydroxy-4-methoxy-benzaldehyde (30 g, 197 mmol) in DCM (anhydrous, 120 rnL) was added pyridine (79 mL, 986 mmol) at room temperature. After the mixture was cooled to -10 ⁰C, the Tf₂O (50 mL, 296 mmol) was slowly added to the reaction between -10 ⁰C to 0 ⁰C. The addition took about 2.5 hours. After the addition, the stirring was kept for 30 minutes. The EtOAc (200 mL) was added. The organic layer was washed with 1 M HCl (3 X 80 mL), dried over MgSO₄, filtered, and evaporated under vacuum. The residue was purified over silica gel, eluting with 5% EtOAc / hexanes to give trifluoro-methanesulfonic acid 2- formyl-5-methoxy-phenyl ester (2) 46 g in 82% yield. ¹H NMR (400 MHz,

CHLOROFORM-^) δ ppm 10.13 (s, 1 H), 7.95 (d, J=8.99 Hz, 1 H), 7.03 (dd, J=8.60, 2.34 Hz, 1 H), 6.88 (d, J=2.34 Hz, 1 H), 3.93 (s, 3 H)

Compound 3:

To a solution of trifluoro-methanesulfonic acid 2-formyl-5-methoxy-phenyl ester (2) (46 g, 160 mmol) in 1,4-dioxane (anhydrous, 360 rnL) were added bis(pinacolato)diboron (82.3 g, 320 mmol), [l,l ‘-bis(diphenylphosphino)ferrocene] palladium(II)chloride (23.7 g, 32 mmol) and KOAc (47.6 g, 480 mmol). The mixture was stirred at room temperature with N₂bubbling for 30 minutes. Then the reaction was heated at 100 ⁰C for 3 hours. The solution was filtered, evaporated under vacuum. The residue was purified over silica gel, eluting with 20% EtOAc / hexanes to afford 4-methoxy-2-(4,4,5,5-tetramethyl-[l,3,2]dioxaborolan-2-yl)-benzaldehyde (3) 37.8 g in 90% yield. ¹H NMR (400 MHz, CHLOROFORM- d) δ ppm 10.34 (s, 1 H), 7.90 (d, J=8.60 Hz, 1 H), 7.26 (s, 1 H), 6.99 (d, J=8.60 Hz, 1 H), 3.86 (s, 3 H), 1.36 (s, 12 H)

Compound 4:

To a clear solution of 4-methoxy-2-(4,4,5,5-tetramethyl-

[l,3,2]dioxaborolan-2-yl)-benzaldehyde (3) (48 g, 180 mmol) in MeOH (anhydrous, 300 mL) was slowly added NaBH₄ (6.96 g, 180 mmol). The reaction was stirred at room temperature for 2 hours. Then IM HCl (100 mL) was slowly added. After stirring for overnight, the MeOH was evaporated under vacuum. The solid was filtered, washed with water and air-dried to afford 6-methoxy-3H- benzo[c][l,2]oxaborol-l-ol (4) 23 g in 77% yield. ¹H NMR (400 MHz, DMSO-J₆) δ ppm 9.11 (s, 1 H), 7.29 (d, J=8.21 Hz, 1 H), 7.23 (d, J=2.34 Hz, 1 H), 7.03 (dd, J=8.40, 2.54 Hz, 1 H), 4.90 (s, 2 H), 3.75 (s, 3 H).

Compound 5:

To a clear solution of 6-methoxy-3H-benzo[c][l,2]oxaborol-l-ol (4) (600 mg, 3.66 mmol) in DCM (anhydrous, 60 mL) was slowly added BBr₃ (1M/DCM, 8.05 mL, 8.05 mmol) at -10 ⁰C. The reaction was stirred for 3 hours, with monitoring by NMR. After all 4 had gone, 30 mL of cold water was added. Then 50 mL of EtOAc was added to extract all organic compounds. The organic layer was washed with cold brine, until the pH of aqueous layer changed to pH 7. The organic layer was dried over Na₂SO₄, filtered, evaporated under vacuum. The residue (-85% HPLC purity) was used directly for the next step reaction without further purification. ¹H NMR (400 MHz, DMSO-J₆) δ ppm 9.29 (s, 1 H), 9.04 (s, 1 H), 7.17 (d, J=8.21 Hz, 1 H), 7.07 (d, J=2.34 Hz, 1 H), 6.85 (dd, J=8.21, 2.34 Hz, 1 H), 4.85 (s, 2 H). ESMS (m/z): 149 (M- H)^“. HPLC: 88.31% (220 nm), 85.02% (maxplot).

Compound 6:

To a solution of 3H-benzo[c][l,2]oxaborole-l,6-diol (5) (300 mg, 2 mmol) in DMSO (30 mL) were added K₂CO₃ (828 mg, 6 mmol) and 3-chloro-4-fiuoro- benzonitrile (933 mg, 6 mmol). The reaction was heated at 90 ⁰C for 7 hours. After the cooling of reaction solution, EtOAc (50 mL) was added. The organic layer was washed with water (5 X 50 mL). The organic layer was evaporated under vacuum. The residue was purified by reverse phase chromatography to afford 3-chloro-4-(l- hydroxy-l,3-dihydro-benzo[c][l,2]oxaborol-6-yloxy)-benzonitrile (6) 190 mg in 33.3% yield. ¹H NMR (400 MHz, DMSO-J₆) δ ppm 9.24 (s, 1 H), 8.22 (s, 1 H), 7.77 (d, J=7.81 Hz, 1 H), 7.50 (d, J=8.20 Hz, 1 H), 7.34 (s, 1 H), 7.28 (d, J=8.20 Hz, 1 H), 7.01 (d, J=8.59 Hz, 1 H), 4.99 (s, 2 H). ESMS (m/z): 284 (M-H)^“. HPLC: 96.41% (220 nm), 96.0% (maxplot).

(X): IS AN 3485

To a clear solution of 3-chloro-4-(l-hydroxy-l,3-dihydro- benzo[c][l,2]oxaborol-6-yloxy)-benzonitrile (6) (136 mg, 0.48 mmol) in THF

(anhydrous, 60 mL) was added lithium aluminum hydride (lM/ether, 1.19 mL, 1.19 mmol) at 0 ⁰C. The reaction was stirred for 2 hours. Then the reaction was quenched with IM HCl (30 mL). MeOH (50 mL) was added and the solution was filtered. The filtrate was evaporated under vacuum. The residue was purified by reverse phase chromatography (biotage, gradient MeOH / H₂O from 10% to 100%) to afford (X) 106 mg (white solid) in 68% yield. ¹H NMR (400 MHz, DMSO-J₆) δ ppm 9.19 (s, 1 H), 8.18 (br, s, 3 H), 7.75 (s, IH), 7.44-7.39 (m, 2 H), 7.19-7.10 (m, 3 H), 4.98 (s, 2 H), 4.03 (q, J=5.50 Hz, 2 H).

ESMS (m/z): 290 (M+H)⁺.

HPLC: 95.9% (220 nm), 96.85% (maxplot).

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