NOVEL QUINOLIN-2-YL NITRONES USEFUL FOR THE PREVENTION AND/OR TREATMENT OF NEURODEGENERATIVE DISEASES

Abstract

The present invention relates to the fields of medicinal chemistry and medicine, and in particular to quinolin-2-yl nitrones with the formula I as pharmaceutically active compounds. These compounds can be used as drugs for the treatment of neurodegenerative diseases by inhibiting BChE or MAO-B, either alone or in combination with other beneficial activities, such as antioxidant properties and metal chelation.

##STR00001##

Claims

1. A compound of formula I, ##STR00017## wherein R.sup.1 represents a -C.sub.1-4 alkyl, a substituted or unsubstituted phenyl or a substituted or unsubstituted benzyl, wherein the phenyl or benzyl, if substituted, is substituted by one or more (such as one, two or three) substituents independently selected from —H, —F, —Cl, —Br, —I, -Me, -Et, —Pr, -iPr, —OMe, —OEt, —OiPr, —OH, —NO.sub.2, —NH.sub.2, —CF.sub.3, and —OCF.sub.3; R.sup.2 represents —H, C.sub.1-4 alkyl, phenyl, halogen, —OR.sup.3 or —NHR.sup.3; R.sup.3 represents —H or -C.sub.1-4 alkyl, and -C.sub.1-4 alkyl is optionally substituted by one or more R.sup.4 groups; each R.sup.4 independently represents halogen, —OH, —OC.sub.1-4 alkyl, —NH.sub.2, —NH(C.sub.1-4 alkyl) or Cy.sub.1; and Cy.sub.1 represents a 5 to 8 member ring, saturated, partially insaturated or aromatic, which contains optionally from 1 to 3 heteroatoms selected among N, O, Se and S; Cy.sub.1 may be attached to rest of the molecule through any C or N atom available, and Cy.sub.1 is optionally substituted by one or more R.sup.5 groups; each R.sup.5 independently represent -C.sub.1-4 alkyl optionally substituted by one or more R.sup.6 ; and each R.sup.6 independently represents -C.sub.2-4 alkynyl, or a pharmaceutically acceptable salt or hydrate thereof.

2. The compound according to claim 1, wherein R.sup.1 is -C.sub.1-4 alkyl.

3. The compound according to claim 1, wherein R.sup.1 is a methyl (CH.sub.3) group or tert-butyl (t-C.sub.4H.sub.9) group.

4. The compound according to claim 1, wherein R.sup.1 is a benzyl (CH.sub.2C.sub.6H.sub.5) group.

5. The compound according to claims 1, wherein R.sup.2 is a hydrogen atom, hydroxyl, a methoxy group, —NH—CH.sub.3, or —N—(CH.sub.3).sub.2.

6. The compound according to claim 1, wherein R.sup.1 is a methyl (CH.sub.3) group, and R.sup.2 is a hydrogen atom, hydroxyl, a methoxy group, —NH—CH.sub.3, or —N—(CH.sub.3).sub.2.

7. The compound according to claim 1, wherein R.sup.1 is a tert-butyl (t-C.sub.4H.sub.9) group, and R.sup.2 is a hydrogen, hydroxyl, a methoxy group, —NH—CH.sub.3, or —N—(CH.sub.3).sub.2.

8. The compound according to claim 1, wherein R.sup.1 is a benzyl (CH.sub.2C.sub.6H.sub.5) group, and R.sup.2 is a hydrogen, hydroxyl, a methoxy group, —NH—CH.sub.3, or —N—(CH.sub.3).sub.2.

9. The compound according to claim 1, selected from the group consisting of: (Z)-N-tert-Butyl-1-(8-(3-(piperidin-1-yl)propoxy)quinolin-2-yl)methanimine oxide; (Z)-N-Benzyl-1-(8-(3-(piperidin-1-yl)propoxy)quinolin-2-yl)methanimine oxide; (Z)-N-tert-Butyl-1-(8-(3-(4-(prop-2-yn-1-yl)piperazin-1-yl)propoxy)quinolin-2-yl)methanimine oxide; (Z)-N-Benzyl-1-(8-(3-(4-(prop-2-yn-1-yl)piperazin-1-yl)propoxy)quinolin-2-yl)methanimine oxide; (Z)-1-(8-Hydroxyquinolin-2-yl)-N-methylmethanimine oxide; (Z)-N-tert-butyl-1-(8-hydroxyquinolin-2-Amethanimine oxide; and (Z)-N-Benzyl-1-(8-hydroxyquinolin-2-Amethanimine oxide.

10. The compound according to claim 1, wherein said compound is (Z)-N-benzyl-1-(8-hydroxyquinolin-2-yl)methanimine oxide.

11. The compound according to claim 1 for use in medicine.

12. A method for prevention and/or treatment of a neurodegenerative disease comprising administering the compound of claim 1 to a subject in need thereof.

13. A pharmaceutical composition comprising the compound according to claim 1, and a pharmaceutically suitable excipient and/or carrier.

14. The pharmaceutical composition according to claim 13 for use in medicine.

15. A method for prevention and/or treatment of a neurodegenerative disease comprising administering the pharmaceutical composition of claim 13 to a subject in need thereof.

16. The method according to claim 12, wherein for the neurodegenerative disease is Alzheimer's disease, Parkinson's disease, or amyotrophic lateral sclerosis.

17. A method, comprising administering the compound according claim 1 as adjuvant therapy for a neurodegenerative disease.

18. A method, comprising administering the pharmaceutical composition accordance to claim 13 as an adjuvant therapy for a neurodegenerative disease.

19. The method of claim 15, wherein the neurodegenerative disease is Alzheimer's disease, Parkinson's disease, or amyotrophic lateral sclerosis.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0006] FIG. 1. Metal chelating properties of compounds 10 and 11. UV-Vis spectra of QNs (A) 10 and (B) 11 (30 μM) alone or in the presence of equimolar quantity of metal ions in buffer (20 mM HEPES, 150 mM NaCl, pH=7.4) at room temperature. UV-vis titration of compounds (C) 10 (30 μM) and (D) 11 with Cu2+ in buffer.

DETAILED DESCRIPTION

Technical Problem

[0007] Several drugs have been approved for the treatment of neurodegenerative diseases, but they cause serious side effects and have limited efficacy in vivo. Therefore, there is an urgent need for the discovery of new drugs for the treatment of neurodegenerative diseases, especially Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis.

Solution to Problem

[0008] The above problem is solved by the present invention based on the surprising finding that quinolin-2-yl nitrones with general formula (I) show pharmacological activities beneficial for the treatment of neurodegenerative diseases.

[0009] The present invention provides in a first aspect a compound of general formula I

##STR00003##

wherein [0010] R.sup.1 represents a -C.sub.1-4 alkyl, a substituted or unsubstituted phenyl or a substituted or unsubstituted benzyl, wherein the phenyl or benzyl, if substituted, is substituted by one or more (such as one, two or three) substituents independently selected from —H, —F, —Cl, —Br, —I, -Me, -Et, —Pr, -iPr, —OMe, —OEt, —OiPr, —OH, —NO.sub.2, —NH.sub.2, —CF.sub.3, and —OCF.sub.3; [0011] R.sup.2 represents —H, -C.sub.1-4 alkyl, phenyl, halogen, —OR.sup.3 or —NHR.sup.3; [0012] R.sup.3 represents —H or -C.sub.1-4 alkyl, with -C.sub.1-4 alkyl being optionally substituted by one or more R.sup.4 groups; [0013] each R.sup.4 independently represents halogen, —OH, —OC.sub.1-4 alkyl, —NH.sub.2, —NH(C.sub.1-4 alkyl) or Cy.sub.1; [0014] Cy.sub.1 represents a 5 to 8-membered ring, saturated, partially unsaturated or aromatic, which contains optionally from 1 to 3 heteroatoms selected among N, O, Se and S; Cy.sub.1 may be attached to rest of the molecule through any C or N atom available, and Cy.sub.1 is optionally substituted by one or more R.sup.5 groups; [0015] each R.sup.5 independently represents -C.sub.1-4 alkyl optionally substituted by one or more R.sup.6; and [0016] each R.sup.6 independently represents -C.sub.2-4 alkynyl.

[0017] According to some embodiments, R.sup.1 is a -C.sub.1-4 alkyl.

[0018] According to some embodiments, R.sup.1 is a substituted or unsubstituted phenyl, wherein the phenyl, if substituted, is substituted by one or more (such as one, two or three) substituents independently selected from —H, —F, —Cl, —Br, —I, -Me, -Et, —Pr, -iPr, —OMe, —OEt, —OiPr, —OH, —NO.sub.2, —NH.sub.2, —CF.sub.3, and —OCF.sub.3;.

[0019] According to some embodiments, R.sup.1 is a substituted or unsubstituted benzyl, wherein the benzyl, if substituted, is substituted by one or more (such as one, two or three) substituents independently selected from —H, —F, —Cl, —Br, —I, -Me, -Et, —Pr, -iPr, —OMe, —OEt, —OiPr, —OH, —NO.sub.2, —NH.sub.2, —CF.sub.3, and —OCF.sub.3;.

[0020] According to some embodiments, R.sup.2 is H.

[0021] According to some embodiments, R.sup.2 is -C.sub.1-4 alkyl.

[0022] According to some embodiments, R.sup.2 is phenyl.

[0023] According to some embodiments, R.sup.2 is halogen.

[0024] According to some embodiments, R.sup.2 is OR.sup.3.

[0025] According to some embodiments, R.sup.3 in OR.sup.3 is H.

[0026] According to some embodiments, R.sup.3 in OR.sup.3 is C.sub.1-4 alkyl, optionally substituted by one or more R.sup.4 groups selected from halogen, —OH, -OC.sub.1-4 alkyl, —NH.sub.2, —NH(C.sub.1-4 alkyl) or Cy.sub.1.

[0027] According to some embodiments, R.sup.3 in OR.sup.3 is C.sub.1-4 alkyl, optionally substituted by Cy.sub.1.

[0028] According to some embodiments, Cy.sub.1 represents a 6-membered ring, saturated, partially unsaturated or aromatic, which contains optionally from 1 to 3, such as 1 or 2, heteroatoms selected among N, O, Se and S; Cy.sub.1 may be attached to rest of the molecule through any C or N atom available, and Cy.sub.1 is optionally substituted by one or more R.sup.5 groups.

[0029] According to some embodiments, Cy.sub.1 represents a 6-membered ring, saturated, partially unsaturated or aromatic, which contains optionally from 1 to 3 N atoms, such as 1 or 2 N atoms; Cy.sub.1 may be attached to rest of the molecule through any C or N atom available, and Cy.sub.1 is optionally substituted by one or more R.sup.5 groups.

[0030] According to some embodiments, R.sup.2 NHR.sup.3.

[0031] According to some embodiments, R.sup.3 in —NHR.sup.3 is H.

[0032] According to some embodiments, R.sup.3 in —NHR.sup.3 is C.sub.1-4 alkyl, optionally substituted by one or more R.sup.4 groups selected from halogen, —OH, —OC.sub.1-4 alkyl, —NH.sub.2, —NH(C.sub.1-4 alkyl) or Cy.sub.1.

[0033] According to some embodiments, R.sup.3 in —NHR.sup.3 is C1-4 alkyl, optionally substituted by Cy.sub.1.

[0034] According to some embodiments, Cy.sub.1 represents a 6-membered ring, saturated, partially unsaturated or aromatic, which contains optionally from 1 to 3, such as 1 or 2, heteroatoms selected among N, O, Se and S; Cy.sub.1 may be attached to rest of the molecule through any C or N atom available, and Cy.sub.1 is optionally substituted by one or more R.sup.5 groups.

[0035] According to some embodiments, Cy.sub.1 represents a 6-membered ring, saturated, partially unsaturated or aromatic, which contains optionally from 1 to 3 N atoms, such as 1 or 2 N atoms; Cy.sub.1 may be attached to rest of the molecule through any C or N atom available, and Cy.sub.1 is optionally substituted by one or more R.sup.5 groups.

[0036] Non-limiting examples of compounds of the present invention are: [0037] compounds of formula I, wherein R.sup.1 is a methyl (CH.sub.3) group, R.sup.2 is a hydrogen atom, hydroxyl, a methoxy group, —NH—CH.sub.3, or —N—(CH.sub.3).sub.2; [0038] compounds of formula I, wherein R.sup.1 is a tert-butyl (t-C.sub.4H.sub.9) group, R.sup.2 is a hydrogen atom, hydroxyl, a methoxy group, —NH—CH.sub.3, or —N—(CH.sub.3).sub.2; and [0039] compounds of formula I, wherein R.sup.1 is a benzyl (CH.sub.2C.sub.6H.sub.5) group, R.sup.2 is a hydrogen atom, hydroxyl, a methoxy group, —NH—CH.sub.3, or —N—(CH.sub.3).sub.2.

[0040] According to some embodiments, the compound is selected from the group consisting of: [0041] (Z)-N-tert-Butyl-1-(8-(3-(piperidin-1-yl)propoxy)quinolin-2-yl)methanimine oxide; [0042] (Z)-N-Benzyl-1-(8-(3-(piperidin-1-yl)propoxy)quinolin-2-yl)methanimine oxide; [0043] (Z)-N-tert-Butyl-1-(8-(3-(4-(prop-2-yn-1-yl)piperazin-1-yl)propoxy)quinolin-2-yl)methanimine oxide; [0044] (Z)-N-Benzyl-1-(8-(3-(4-(prop-2-yn-1-yl)piperazin-1-yl)propoxy)quinolin-2-yl)methanimine oxide; [0045] (Z)-1-(8-Hydroxyquinolin-2-yl)-N-methylmethanimine oxide; [0046] (Z)-N-tert-butyl-1-(8-hydroxyquinolin-2-yl)methanimine oxide; and [0047] (Z)-N-Benzyl-1-(8-hydroxyquinolin-2-yl)methanimine oxide.

[0048] A Particularly preferred compound of the present invention is quinolin-2-yl nitrone (Z)-N-benzyl-1-(8-hydroxyquinolin-2-yl)methanimine oxide, which structural formula (formula II) is described below:

##STR00004##

[0049] (Z)-N-Benzyl-1-(8-hydroxyquinolin-2-yl)methanimine oxide showed striking antioxidant capacity against hydroxyl radicals and thus a remarkable activity for neuroprotection of primary cultured neurons after experimental ischemia, as well as a very potent and selective capacity to inhibit human MAO-B and human BChE, as well as strong bio-metal (Zn, Fe, Cu) chelating properties.

[0050] Pharmaceutically acceptable pro-drugs, polymorphs, salts and hydrates of any of the above compounds of formula I are included within the present invention.

[0051] As used herein, the term “C.sub.1-4 alkyl” means a straight or branched chain non-cyclic hydrocarbon having 1, 2, 3 or 4 carbon atoms. The term “C.sub.1-4 alkyl” includes methyl, ethyl, propyl, isopropyl, butyl, sec-butyl and tert-butyl. Preferred examples of “C.sub.1-4 alkyl” are methyl and tert-butyl.

[0052] As used herein, the term “C.sub.2-4 alkynyl” means a straight or branched chain non-cyclic hydrocarbon having 2, 3 or 4 carbon atoms and including at least one carbon-carbon triple bond. The term “C.sub.2-4 alkynyl” includes ethynyl, 2-propynyl, 3-propynyl, 2-butynyl and 3-butynyl.

[0053] It is noted that any of the compounds mentioned as examples throughout the present invention can be used separately or in combination, particularly as adjuvant therapy administered simultaneously, alternatively or successively with respect to a first-line therapy suitable for the treatment of a neurodegenerative disease, such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis.

[0054] Therefore, in a further aspect the present invention provides a pharmaceutical composition comprising a compound of the present invention, or geometric isomers thereof, and a pharmaceutically acceptable excipient and/or carrier.

[0055] In a further aspect the present invention provides a compound or pharmaceutical composition of the present invention for use in medicine.

[0056] In a further aspect the present invention provides a compound or pharmaceutical composition of the present invention for use in the treatment of a neurodegenerative disease, such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis.

[0057] In a further aspect the present invention provides a compound or pharmaceutical composition of the present invention for use as adjuvant therapy.

[0058] The adjuvant therapy may be administered simultaneously, alternatively or successively with respect to a first-line therapy suitable for the treatment of a neurodegenerative disease, such as Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis.

[0059] The invention is illustrated, though not limited, by the following examples:

EXAMPLES

[0060] General Synthesis Methods. Reactions were monitored by TLC using precoated silica gel aluminium plates containing a fluorescent indicator (Merck, 5539). Detection was done by UV (254 nm) followed by charring with sulfuric-acetic acid spray, 1% aqueous potassium permanganate solution or 0.5% phosphomolybdic acid in 95% EtOH. Anhydrous Na.sub.2SO.sub.4 was used to dry organic solutions during work-ups and the removal of solvents was carried out under vacuum with a rotary evaporator. Flash column chromatography was performed using silica gel 60 (230-400 mesh, Merck). Melting points were determined on a Kofler block and are uncorrected. IR spectra were obtained on a Perkin-Elmer Spectrum One spectrophotometer. .sup.1H NMR spectra were recorded with a Varian VXR-200S spectrometer, using tetramethylsilane as internal standard and .sup.13C NMR spectra were recorded with a Bruker WP-200-SY. All the assignments for protons and carbons were in agreement with 2D COSY, HSQC, HMBC, and 1D NOESY spectra. Values with (*) can be interchanged. The purity of compounds was checked by elemental analyses, conducted on a Carlo Erba EA 1108 apparatus, and confirmed to be ≥95%.

[0061] General procedure for the synthesis of nitrones. A solution of the corresponding carbaldehyde (1 mmol), Na.sub.2SO.sub.4 (3 mmol), AcONa (2 mmol) and the appropriate N-alkylhydroxylamine hydrochloride (1.5 mmol) in EtOH (5 mL) was heated at 90° C. for 2-3 h under MWI. After that time, the solvent was evaporated and the crude mixture was purified on column chromatography using the indicated mixtures of solvents.

##STR00005##

Synthesis of Compounds 3 and 4

[0062] 8-(3-(Piperidin-1-yl)propoxy)quinoline-2-carbaldehyde (2). A solution of commercial 8-hydroxyquinoline-2-carbaldehyde (1) (103.9 mg, 0.6 mmol) in CHCl.sub.3 (3.6 mL)/ water (0.6 mL), K.sub.2CO.sub.3 (249 mg, 1.8 mmol) and commercial 1-(3-chloropropyl)piperidine (178.32 mg, 0.9 mmol) were added. The mixture was vigorously stirred and heated at 80° C. for 1 d. After that time, the solvent was evaporated under reduced pressure and the crude mixture was purified on column chromatography (DCM/MeOH 7%) to yield compound 2 as a yellow solid (158.7 mg, 89%): mp 44-6° C.; IR (KBr) ν 2932, 1709, 1462, 1323, 1102 cm.sup.−1;.sup.1H NMR (400 MHz, CDCl.sub.3) δ 10.20 (s, 1H), 8.18 (dd, J=8.5, 0.9 Hz, 1H), 7.97 (d, J=8.4 Hz, 1H), 7.52 (t, J=8.0 Hz, 1H), 7.37 (dd, J=8.3, 1.1 Hz, 1H), 7.12 (dd, J=7.9, 1.2 Hz, 1H), 4.29 (t, J=6.8 Hz, 2H), 2.62-2.51 (m, 2H), 2.50-2.30 (m, 4H), 2.25-2.12 (m, 2H), 1.55 (p, J=5.6 Hz, 4H), 1.39 (q, J=5.7, 4.3 Hz, 2H); .sup.13C NMR (101 MHz, CDCl.sub.3) δ 193.9, 155.5, 151.4, 140.1, 137.2, 131.4, 129.8, 119.5, 117.7, 109.9, 67.9, 55.78, 54.6 (2C), 26.33, 25.8 (2C), 24.3. HRMS (ESI_ACN) Calcd. for C.sub.18H.sub.22N.sub.2O.sub.2: 298.1682. Found: 298.1690.

[0063] (Z)-N-tert-Butyl-1-(8-(3-(piperidin-1-yl)propoxy)quinolin-2-yl)methanimine oxide (3). Following the general method for the synthesis of nitrones, a solution of carbaldehyde 2 (79.35 mg, 0.27 mmol), Na.sub.2SO.sub.4 (76.68 mg, 0.54 mmol), AcONa (26.57 mg, 0.324 mmol) and N-tert-butylhydroxylamine hydrochloride (40.69 mg, 0.324 mmol) in EtOH (5 mL) was heated at 95° C. for 3 h under MWI. Then, the solvent was evaporated and the crude mixture was purified on column chromatography (DCM/MeOH 7%) to yield compound 3 as a yellow solid (52.3 mg, 52%): mp 135-7° C.; IR (KBr) ν 3493, 2942, 1615, 1261, 1096 cm.sup.−1; .sup.1H NMR (400 MHz, CDCl .sub.3) δ 9.27 (d, J=8.8 Hz, 1H), 8.36-8.13 (m, 1H), 7.53-7.41 (m, 2H), 7.16-7.04 (m, 1H), 4.37 (t, J=5.7 Hz, 2H), 3.61 (d, J=11.9 Hz, 2H), 3.43-3.28 (m, 2H), 2.68 (dd, J=15.8, 6.7 Hz, 4H), 2.32 (d, J=13.8 Hz, 2H), 2.00-1.79 (m, 4H), 1.67 (s, 9H); .sup.13C NMR (101 MHz, CDCl.sub.3) δ 137.5, 132.1, 129.6, 127.6, 127.5, 121.9, 120.4, 119.1, 110.2, 110.0, 72.5. 66.7, 55.4, 53.5 (2C), 28.4 (3C), 23.9, 22.7 (2C), 22.2. HRMS (ESI_ACN) Calcd. for C.sub.22H .sub.31N.sub.3O.sub.2: 369.24163. Found: 369.24136.

[0064] (Z)-N-Benzyl-1-(8-(3-(piperidin-1-yl)propoxy)quinolin-2-yl)methanimine oxide (4). Following the general method for the synthesis of nitrones, a solution of carbaldehyde 2 (79.35 mg, 0.27 mmol), Na.sub.2SO.sub.4 (76.68 mg, 0.54 mmol), AcONa (26.57 mg, 0.324 mmol) and N-benzylhydroxylamine hydrochloride (51.71 mg, 0.324 mmol) in EtOH (5 mL) was heated at 90° C. for 2 h under MWI. After that time, the solvent was evaporated and the crude mixture was purified on column chromatography (DCM/MeOH 7%) to yield compound 4 as a mixture of Z and E isomers in a 3.5:1 ratio, that we were unable to separate, as a yellow solid (59.7 mg, 55%): mp 108-10° C.; IR (KBr) ν 3420, 2935, 1600, 1455, 1105 cm.sup.−1; .sup.1H NMR (400 MHz, CDCl.sub.3) [(minor isomer E) 8.17 (d, J=8.8 Hz, 1H, H4), 7.79 (s, 1H, CH═N), 7.74 (dd, J=8.4, 1.1 Hz, 1H, H3), 7.55 (dd, J=7.0, 2.5 Hz, 1 H, H5), 7.09 (br d, J=1.5 Hz, 1H, H7), 5.43 (s, 1H, CH.sub.2C.sub.6H.sub.5), (major isomer Z) 9.15 (d, J=8.8 Hz, 1H, H4), 8.17 (d, J=8.8 Hz, 1H, H3), 8.08 (s, 1H, CH═N), 7.07 (br d, J=7.5 Hz, 1H, H7), 5.15 (s, 1H, CH.sub.2C.sub.6H.sub.5)], 8.28-8.26 (m, 1H, C.sub.6H.sub.5), 7.54 (br d, J=Hz, 1H, H5), 7.44-7.38 (m, 6H, H6, C.sub.6H.sub.5), 7.45 (t, J=Hz, 1H, H6), 7.52-7.37 (m, 4H, C.sub.6H.sub.5), 4.31 (t, J=Hz., 2H, OCH.sub.2), 3.15-2.65 (m, 6H), 2.43-2.41 (m, 2H), 1.98-1.70 (m, 4H), 1.65-1.51 (m, 2H). HRMS (ESI_ACN) Calcd. for C.sub.25H.sub.29N.sub.3O.sub.2: 403.22598. Found: 403.22528.

##STR00006##

Synthesis of QNs 7 and 8

[0065] 1-(3-Chloropropyl)-4-(prop-2-yn-1-yl)piperazine (5). To solution of commercial 1-(3-chloropropyl)piperazine dihydrochloride (702 mg, 3 mmol, 1 equiv), TEA (0.84 mL, 6 mmol, 2 equiv) in dry CH.sub.2Cl.sub.2 (5 mL), cooled at 0° C., propargyl bromide (0.81 mL, 9 mmol, 3 equiv) was added over 30 min under Ar. The mixture was stirred at rt for 24 h and then treated with a saturated sodium bicarbonate solution (10 mL). The organic layer was separated and washed with saturated brine, and dried over anhydrous sodium sulfate. The solvent was removed under reduced pressure and the residue purified by column chromatography through silica gel (CH.sub.2Cl.sub.2/MeOH 1%-2%), to yield 5 (312 mg, 52%) as a colorless oil: .sup.1H NMR (400 MHz, CDCl.sub.3) δ 3.53 (t, J=6.6 Hz, 2H), 3.23 (d, J=2.5 Hz, 2H), 2.54-2.39 (m, 10H), 2.18 (t, J=2.5 Hz, 1H), 1.88 (p, J=6.7 Hz, 2H); .sup.13C NMR (101 MHz, CDCl.sub.3) δ 78.8, 73.2, 55.4, 53.1 (2C), 51.9 (2C), 46.8, 43.2, 29.9.

[0066] 8-(3-(4-(Prop-2-yn-1-yl)piperazin-1-yl)propoxy)quinoline-2-carbaldehyde (6). A solution of commercial 8-hydroxyquinoline-2-carbaldehyde (1) (91.69 mg, 0.53 mmol) in CHCl.sub.3 (5 mL) was added K.sub.2CO.sub.3 (219.42 mg, 1.59 mmol) and 1-(3-chloropropyl)-4-(prop-2-yn-1-yl)piperazine (5) (138 mg, 0.69 mmol); then, water (1 mL) was added. The mixture was vigorously stirred and heated at 80° C. for 2 d. After that time, the solvent was evaporated under reduced pressure and the crude mixture was purified on column chromatography (DCM/MeOH 4%) to yield compound 6 as a yellow solid (95.5 mg, 53%): mp 99-101° C.; IR (KBr) ν 3128, 2829, 1715, 1462, 1320, 1094 cm.sup.−1; .sup.1H NMR (400 MHz, CDCl.sub.3) δ 10.20 (s, 1H), 8.20 (d, J=8.4 Hz, 1H), 7.98 (d, J=8.5 Hz, 1H), 7.53 (t, J=8.5 Hz, 1H), 7.39 (d, J=8.5 Hz, 1H), 7.13 (d, J=8.4 Hz, 1H), 4.31 (t, J=6.5 Hz, 2H), 3.24 (s, 2H), 2.76-2.36 (m, 10H), 2.26-2.13 (m, 3H); .sup.13C NMR (101 MHz, CDCl.sub.3) δ 193.8, 155.5, 151.4, 140.1, 137.2, 131.4, 129.8, 119.6, 117.8, 110.0, 78.8, 73.2, 67.7, 55.0, 53.0 (2C), 51.8 (2C), 46.8, 26.3. HRMS (ESI_ACN) Calcd. for C.sub.20H.sub.23N.sub.3O.sub.2: 337.1790. Found: 337.1790.

[0067] (Z)-N-tert-Butyl-1-(8-(3-(4-(prop-2-yn-1-yl)piperazin-1-yl)propoxy)quinolin-2-yl)methanimine oxide (7). Following the general method for the synthesis of nitrones, the reaction of carbaldehyde 6 (69 mg, mmol) with Na.sub.2SO.sub.4 (57 mg, 0.4 mmol), AcONa (26 mg, 0.32 mmol) and N-tert-butylhydroxylamine hydrochloride (38 mg, 0.3 mmol) in EtOH (5 mL) after 5 min, and column chromatography (DCM/MeOH 3%) yielded compound 7 as a yellow gum (55.7 mg, 66%): IR (KBr) ν 3428, 2819, 1451, 13206, 1155, 1104 cm.sup.−1; .sup.1H NMR (400 Hz, CDCl.sub.3) δ 9.26 (d, J=8.8 Hz, 1H), 8.19 (d, J=8.8 Hz, 1H), 8.13 (s, 1H), 7.44-7.38 (m, 2H,), 7.08-7.06 (m, 1H), 4.29 (t, J=6.9 Hz, 2H), 3.30-3.28 (m, 2H), 2.63 (s, 10H), 2.32-2.17 (m, 3H), 1.65 (s, 9H); .sup.13C NMR (126 MHz, CDCl.sub.3) δ 154.6, 149.8, 140.2, 136.6, 132.6, 129.5, 127.3, 121.7, 119.5, 109.0, 78.7, 73.4, 72.0, 67.7, 55.0, 53.0 (2C), 51.8 (2C), 46.8, 28.3 (3C), 26.3. HRMS (ESI_ACN) Calcd for C.sub.24H.sub.32N.sub.4O.sub.2: 408,2525. Found: 408,2525.

[0068] (Z)-N-Benzyl-1-(8-(3-(4-(prop-2-yn-1-yl)piperazin-1-yl)propoxy)quinolin-2-yl)methanimine oxide (8). Following the general method for the synthesis of nitrones, a solution of carbaldehyde 6 (95.5 mg, mmol), treated with Na.sub.2SO.sub.4 (79.52 mg, 0.56 mmol), NaHCO.sub.3 (35.28 mg, 0.42 mmol) and N-benzylhydroxylamine hydrochloride (67.03 mg, 0.42 mmol), in THF (5 mL), reacted instantly. After that time, the solvent was evaporated and the crude mixture was purified on column chromatography (DCM/MeOH 3%) to yield compound 8 as a mixture of E and Z isomers in a 1.5:1 ratio, that we were unable to separate, as a yellow gum (92.5 mg, 75%): IR (KBr) ν 3429, 2817, 1457, 1320, 1151, 1104 cm.sup.−1; .sup.1H NMR (500 MHz, CDCl.sub.3) δ [(major isomer E) 8.17 (d, J=8.5 Hz, 1H, H4), 7.81 (d, J=8.5 Hz, 1H, H3), 7.75 (s, 1H, CH═N), 7.55 (dd, J=7.8, 1.7 Hz, 1H, H5), 7.12 (dd, J=7.7, 1.2 Hz, 1H, H7), 5.44 (s, 1H, CH.sub.2C.sub.6H.sub.5), 3.30 (d, J=2.4 Hz, 2H, CH.sub.2C≡CH), (minor isomer Z) 9.18 (d, J=8.7 Hz, 1H, H4), 8.19 (d, J=8.7 Hz, 1H, H3), 8.06 (s, 1H, CH═N), 7.10 (dd, J=7.7, 1.3 Hz, 1H, H7), 5.14 (s, 1H, CH.sub.2C.sub.6H.sub.5), 3.31 (d, J=2.4 Hz, 2H, CH.sub.2C≡CH)], 8.26-8.24 (m, 1H, C.sub.6H.sub.5), 7.45 (t, J=Hz, 1H, H6), 7.52-7.37 [m, 4H, H5 (minor)], C.sub.6H.sub.5), 4.31 (t, J=Hz, 2H, OCH.sub.2), 2.75-2.50 (m, 10H), 2.25-2.24 (m, 1H, CH.sub.2C≡CH), 2.24-2.16 (h, J=Hz, 2H, NCH.sub.2CH.sub.2CH.sub.2O). HRMS (ESI_ACN) Calcd for C.sub.27H.sub.30CIN.sub.4O.sub.2: 442.2369. Found: 442.2369.

##STR00007##

Synthesis of QNs 9-11

[0069] (Z)-1-(8-Hydroxyquinolin-2-yl)-N-methylmethanimine oxide (9). Following the general method for the synthesis of nitrones, the reaction of 8-hydroxyquinoline-2-carbaldehyde (1) (173 mg, 1 mmol, 1 equiv) with Na.sub.2SO.sub.4 (426 mg, 3 mmol, 3 equiv), AcONa (160 mg, 2 mmol, 1.6 equiv) and N-methylhydroxylamine hydrochloride (239 mg, 1.5 mmol, 1.5 equiv) in EtOH (7 mL) at 90° C. for 10 min, after column chromatography (hexane/AcOEt 9/1) yielded compound 9 as a pale yellow solid (171 mg, 85%): 149-151° C.; .sup.1H NMR (300 MHz, CDCl.sub.3) δ 9.16 (d, J=8.8 Hz, 1H), 8.25 (d, J=8.8 Hz, 1H), 8.03 (br s, 1H), 7.86 (s, 1H), 7.51-7.46 (m, 1H), 7.36 (dd, J=7.6, 1.3 Hz, 1H), 7.18 (dd, J=7.6, 1.3 Hz, 1H), 4.01 (s, 3H); .sup.13C NMR (100 MHz, CDCl.sub.3) δ 152.1, 147.7, 138.1, 136.8, 136.4, 128.7, 128.6, 121.4, 117.8, 110.1, 55.1. HRMS (ESI_ACN) Calcd. for C.sub.11H.sub.10N.sub.2O.sub.2: 202,0742. Found 202,0742.

[0070] (Z)-N-tert-butyl-1-(8-hydroxyquinolin-2-yl)methanimine oxide (10). Following the general method for the synthesis of nitrones, the reaction of 8-hydroxyquinoline-2-carbaldehyde (1) (173 mg, 1 mmol, 1 equiv) with Na.sub.2SO.sub.4 (426 mg, 3 mmol, 3 equiv), AcONa (160 mg, 2 mmol, 1.6 equiv) and N-tert-butylhydroxylamine hydrochloride (188 mg, 1.5 mmol, 1.5 equiv) in EtOH (7 mL) at 90° C. for 5 min, after column chromatography (hexane/AcOEt 9/1), yielded compound 10 as a pale yellow solid (159 mg, 92%): 103-4° C.; .sup.1H NMR (400 MHz, CDCl.sub.3) δ 9.16 (d, J=8.8 Hz, 1H), 8.16 (d, J=8.8 Hz, 1H), 8.04 (br s , 1H), 7.97 (s, 1H), 7.41-7.39 (m, 1H), 7.27 (dd, J=7.6, 1.2 Hz, 1H), 7.09 (dd, J=7.6, 1.2 Hz, 1H), 1.62 (s, 9H); .sup.13C NMR (100 MHz, CDCl.sub.3) δ 152.0, 148.5, 138.1, 136.7, 131.5, 128.5, 128.4, 121.7, 117.8, 110.0, 72.1, 28.4 (3C). HRMS (ESI_ACN) Calcd. for C.sub.14H.sub.16N.sub.2O.sub.2: 244,1212. Found 244,1212.

[0071] (Z)-N-Benzyl-1-(8-hydroxyquinolin-2-yl)methanimine oxide (11). Following the general method for the synthesis of nitrones, the reaction of 8-hydroxyquinoline-2-carbaldehyde (1) (173 mg, 1 mmol, 1 equiv), Na.sub.2SO.sub.4 (426 mg, 3 mmol, 3 equiv.), AcONa (160 mg, 2 mmol, 1.6 equiv.) and N-benzylhydroxylamine hydrochloride (239 mg, 1.5 mmol, 1.5 equiv.) in EtOH (7 mL) was heated at 90° C. during 10 min under mw irradiation. After that time, the solvent was evaporated and the crude mixture was purified on column chromatography (Hexanes/AcOEt 9/1) to yield compound 11 as a pale yellow solid (272 mg, 98%): 110-1° C.; .sup.1H NMR (400 MHz, CDCl.sub.3) δ 9.15 (d, J=8.8 Hz, 1H), 8.22 (d, J=8.8 Hz, 1H), 8.00 (br s, 1H), 7.88 (s, 1H), 7.55-7.51(m, 2H), 7.44-7.37 (m, 4H), 7.26 (dd, J=7.6, 1.2 Hz, 1H), 7.08 (dd, J=7.6, 1.2 Hz, 1H), 5.09 (s, 2H); .sup.13C NMR (100 MHz, CDCl.sub.3) δ 152.1, 147.7, 138.1, 136.8, 135.3, 132.7, 129.5 (2C), 129.3, 129.2 (2C), 128.7, 128.6, 121.6, 117.8, 110.1, 72.1. HRMS (ESI_ACN) Calcd. for C.sub.17H.sub.14N.sub.2O.sub.2: 278,1055. Found 278,1055.

Pharmacological Evaluation

[0072] Inhibition of Cholinesterases. The inhibitory potencies of compounds against the ChEs were determined by the method of Ellman (Ellman, G. L.; Courtney, K. D.; Andres, V.; Featherstone, R. M. Biochem. Pharmacol. 1961, 7, 88-95). Briefly, compounds were incubated with Ellman's reagent (final concentration, 370 μM) and the ChEs (final concentration, approx. 1 nM or 100 μM hBChE or hAChE, respectively) in 0.1 M sodium phosphate (pH 8.0) for 5 min at 20° C. on 96-well microplates (Brand microplate, pureGrade, F-bottom). Reactions were started adding the substrate (final concentration, 500 μM butyrylthiocholine iodide [BTCI] or acetylthiocholine iodide [ATCI] for hBChE and hAChE, respectively). The final content of DMSO was always 1% (v/v). The increase in absorbance (λ=412 nm) was monitored for 2 min using a microplate reader (Synergy HT, BioTek Instruments, VT, USA). The initial velocities in the presence (vi) and absence (vo) of the compounds were calculated, and the inhibitory potencies were expressed as residual activities (RA=vi/vo). The IC.sub.50 values were determined by plotting RA against the applied inhibitor concentrations, with the experimental data fitted to a four-parameter logistic function (GraphPad Prism 9.3, GraphPad Software, San Diego, CA, USA). Donepezil was used as a positive control (Table 1).

[0073] Inhibition of Monoamine Oxidases. Recombinant microsomal hMAOs expressed in BTI-TN-5B1-4 cells, HRP (type II, lyophilized powder) and p-tyramine hydrochloride were purchased from Sigma Aldrich (Sigma Aldrich, MO, USA). 10-Acetyl-3,7-dihydroxyphenoxazine (Amplex Red) was synthesized as described previously (von der Eltz, H.; DE; Guder, H.-J.; DE; Muhlegger, K.; DE. U.S. Pat. No. 5,035,998—Hydrolase Substrates. U.S. Pat. No. 5,035,998, Jul. 30, 1991). Briefly, 100 μL of 50 mM sodium phosphate (pH 7.4, 0.05% [v/v] Triton X-114) containing the test compounds, and hMAO-A or hMAO-B were incubated at 37° C. for 15 min in 96-well microplates (Nunc Microwell microplates, Thermo Fisher). After preincubation, the reaction was started by adding Amplex Red (final concentration, 200 μM), HRP (2 U/mL), and p-tyramine (1 mM). The increase in fluorescence intensity (λex=530 nm, λem=590 nm) was monitored at 37° C. for 30 min using a microplate reader (Synergy HT; BioTek Instruments, Inc., VT, USA). DMSO was used for control experiments (1%, v/v). To determine the blank value (b), sodium phosphate buffer replaced the enzyme solution. Initial velocities were calculated from the trends obtained, with each measurement performed in duplicate. The inhibitory potencies are expressed as the RAs according to equation: RA=(vi−b)/(vo−b), where vi is the velocity in the presence of the test compounds, and v0 is the control velocity in the presence of DMSO. IC.sub.50 values were determined by plotting the residual MAO activities against the applied inhibitor concentrations, with the experimental data fitted to a Hill four-parameter equation (GraphPad Prism 9.3, GraphPad Software, San Diego, CA, USA). For the reversibility assay, hMAO-B was incubated at 100-fold final concentration with the inhibitors at IC50 concentration at 37° C. (volume, 50 μL). After 15 min, the mixture was diluted 100-fold into the reaction buffer containing Amplex Red, HRP, and p-tyramine hydrochloride. The final concentrations of all reagents and of hMAO-B were the same as described above. Control experiments were performed in the same manner, replacing the inhibitor solution with DMSO (Table 1).

TABLE-US-00001 TABLE 1 In vitro MAO and ChE inhibitory potencies of compounds and positive controls. IC.sub.50 ± SEM [μM].sup.a Compound Structure hMAO-A hMAO-B hAChE hBChE 3 [00008] n.a..sup.b n.a..sup.b n.a..sup.b,c 0.0254 ± 0.0021 4 [00009] n.a..sup.b n.a..sup.b n.a..sup.b,c 0.0769 ± 0.0063 7 [00010] n.a..sup.b n.a..sup.b n.a..sup.b 0.0073 ± 0.0011 8 [00011] n.a..sup.b,c n.a..sup.b n.a..sup.b 0.0310 ± 0.0064 9 [00012] n.a..sup.b,c 10.1 ± 2.5 n.a..sup.b n.a..sup.b 10 [00013] n.a..sup.b 16.4 ± 1.0 n.a..sup.b 0.0051 ± 0.0006 11 [00014] n.a..sup.b 4.46 ± 0.18 0.0290 ± 0.0030 0.0011 ± 0.00031.sup.d Donepezil [00015] n.d..sup.e n.d..sup.e 0.0220 ± 0.0024 4.15 ± 0.56 Safinamide [00016] n.a..sup.b 0.029 ± 0.002 n.d..sup.e n.d..sup.e .sup.aSEM, standard error of the mean, IC.sub.50 values are average of three independent experiments, each performed in triplicate; .sup.bn.a., not active (residual activity - RA at 100 μM ≥50%). .sup.cnonspecific inhibition at the screening concentration (100 μM) due to solubility issues, inhibition disappears upon dilution (10 μM). .sup.dIC.sub.50 value do not reflect the true affinity of the compound due to the IC.sub.50 value approaching the concentration of the hBChE (approx. 1 nM) in the in vitro assays.

[0074] DPPH radical-scavenging potency of compounds 10 and 11. Free-radical scavenging potency was evaluated using the DPPH assay. DPPH (2,2-diphenyl-1-picrylhydrazyl radical) was dissolved in MeOH (150 μL, 140 μM) and added to 150 μL methanol solution of the test sample (screening at 100 μM, serial dilution of compounds for EC.sub.50 determination) or methanol (negative control) on 96-well microtiter plates (Brand microplate, pureGrade, F-bottom). The microtiter plate was incubated at room temperature in the dark for 90 min. The absorbance at 517 nm was then determined with a microplate reader (Synergy HT; BioTek Instruments, Inc., VT, USA). The experiments were performed in triplicate, with subtraction of the blank value (compound without DPPH). The percentages of DPPH free radicals were calculated as DPPH free radical (%)=[(A0−A1)/A0]×100, where A0 is the absorbance of the negative control, and A1 is the absorbance of the test sample. The free-radical scavenging potency is expressed as the concentration that scavenged 50% of the DPPH free radicals (EC.sub.50)±SEM. Compounds 10 and 11 displayed the free-radical scavenging potency with EC.sub.50 values of 119.2±1.2 μM and 126.0±0.1 μM, respectively. Resveratrol and Trolox were used as the positive controls under the same assay conditions.

[0075] Metal-chelating properties of 10 and 11. The chelation properties were determined in HEPES buffer (20 mM, 150 mM NaCl, pH 7.4) using a 96-well microplate reader (Synergy HT; BioTek Instruments, Inc., VT, USA). To determine the chelation of the metal ions by the compounds, 30 μM compound solution was treated with equimolar concentrations of CuCl.sub.2, ZnCl.sub.2, CoCl.sub.2, MgCl.sub.2, CaCl.sub.2, FeCl.sub.2, FeCl.sub.3, and AlCl.sub.3. To prevent oxidation of Fe.sup.2+, the solution of FeCl.sub.2 was prepared in the presence of 1 mM ascorbic acid. The absorption spectra were recorded after 30 min incubation at room temperature. The chelation was detected by the change in the absorption spectra, which was specific for each metal ion. The Cu.sup.2+ binding stoichiometry was resolved by titration of a 30 μM buffered solution of the compounds with additions of CuCl.sub.2 buffered stock solution. The absorption of the compounds in the absence and presence of increasing Cu.sup.2+ concentrations (0-150 μM) were recorded at the most responsive wavelength after 30 min incubation at room temperature. The absorbance differences in the absence and presence of Cu.sup.2+ were plotted against the Cu.sup.2+/compound molar ratio. The curves were approximated using data points at the lowest and highest Cu.sup.2+/compound ratios, and the intercepts were calculated (Yoe-Jones method) (Bosque-Sendra, J. M.; Almansa-López, E.; Garcia-Campana, M.; Cuadros-Rodriguez, L. Anal. Sci. 2003, 19, 1431-1439).

[0076] The absorption spectra of 10 (λabs, max=286 nm) incubated with equimolar quantity of Zn.sup.2+, Cu.sup.2+, and Al.sup.3+ showed characteristic bathochromic shift with new absorption maxima at 309, 310 and 296 nm, respectively (FIG. 1A), whereas addition of Fe.sup.2+ and Fe.sup.3+ resulted in hyperchromic shift, i.e., the increase in absorbance at 286 nm, and appearance of secondary maxima at ˜230 nm. On the other hand, no major changes in absorption spectra were observed for Ca.sup.2+ and Mg.sup.2+ ions. Similar was observed for nitrone 19 (λabs, max=287 nm): i) appearance of maxima at 310, 311 and 296 nm for Zn.sup.2+, Cu.sup.2+, and Al.sup.3+, respectively; ii) hypochromic change in absorbance spectra for 19 in the presence of Fe.sup.2+ and Fe.sup.3+, and iii) no major alterations in spectra upon incubation with Ca.sup.2+ and Mg.sup.2+ (FIG. 1B). This indicated that both QNs generated corresponding complexes with Zn.sup.2+, Cu.sup.2+, Al.sup.3+, Fe.sup.2+ and Fe.sup.3+, whereas they did not chelate Ca.sup.2+ and Mg.sub.2+. Copper ion is of particular interest in AD,59,60 thus the stoichiometry of the Cu2+ complexes with compounds 10 and 11 was determined by Yoe-Jones method,61 which showed an interception point at 0.5 indicating 10-Cu.sup.2+ and 11-Cu.sup.2+ complexes with a 1:2 Cu.sup.2+/compound molar ratio (FIG. 1).