Substituted oxygenated heterocycles and thio-analogues: synthesis and biological evaluation as melatonin ligands

A new series of substituted oxygenated heterocycles and thio-analogues were synthesized and evaluated as melatonin receptor ligands. The replacement of the indolic moiety of melatonin by heterocyclic skeleton such as 1,4-benzodioxin, 2,3-dihydro-1,4-benzodioxin, chroman, 2,3-dihydro-1,4-benzoxathiin, thiochroman, carrying the amidic chain on the aromatic ring, leads to compounds showing a weak affinity for melatonin receptors, except for the compounds 1cb and 1hb.

Comparison of sulfobutylether- and sulfated-beta-cyclodextrins as additives for the chiral separation of basic spirobenzopyrans by capillary electrophoresis

Three charged substituted beta-cyclodextrins (beta-CDs), sulfobutylether-beta-(SBE-beta-CD), degree of substitution (DS) 4 and 7), and sulfated-beta-(S-beta-CD) cyclodextrins, were compared as chiral additives in capillary electrophoresis for the enantiomeric separation of basic spirobenzopyran derivatives (pKa 9.9) which differ from each other by an N-alkyl group. The number of sulfobutylether groups attached to the cyclodextrin moiety significantly influences the enantioseparation of the basic drugs. SBE-beta-CD (DS 7) which is more strongly bound to cationic analyte than SBE-beta-CD (DS 4.6), requires smaller concentrations to achieve the same resolution. Besides, better enantioresolutions were obtained with S-beta-CD rather than with SBE-beta-CDs though higher concentrations are required, which led to high current values. However, both pairs of enantiomers cannot be resolved using S-beta-CD while SBE-beta-CDs make it possible to resolve simultaneous enantioseparation of such solutes slightly differing in hydrophobicity. This supports the hypothesis that hydrophobic interactions (outside of the CD cavity) between the butyl group attached to SBE-beta-CD and the N-alkyl group of spirobenzopyran play a role in the enantioseparation. On the other hand, the sulfate group of S-beta-CD was directly attached to the CD moiety which means that the S-beta-CD-drug complexation mechanism arises through the combination of electrostatic and hydrophobic (inside the CD cavity) interactions. Finally, enantiomers of spirobenzopyran drugs were satisfactorily resolved by CE using a 20 mg/mL S-beta-CD concentration (resolution 4.0), 7 mg/mL SBE-beta-CD DS 4 (resolution 1.3), or 5 mg/mL SBE-beta-CD DS 7 (resolution 3.3) added to the phosphate buffer (pH 2.6, 50 mM ionic strength).

N,N-disubstituted aminomethyl benzofuran derivatives: synthesis and preliminary binding evaluation

A series of new N-substituted 2,3-dihydro-2-aminomethyl-2H-1-benzofuran derivatives was prepared and evaluated for affinity at 5-HT1A, 5-HT2A, 5-HT2C, 5-HT3, D2, and D3 receptors. Compound 9, 8-[4-[N-propyl-N-(7-hydroxy-2,3-dihydro -2H-1-benzofuran-2-yl)methyl]aminobutyl]-8-azaspiro[4,5]decane-7,9 -dione, bound at 5-HT1A sites with nanomolar affinity (IC50= 1.5 nM) and high selectivity over 5-HT2A, 5-HT2C, 5-HT3, D2, and D3 receptors.

Pharmacophoric search and 3D-QSAR comparative molecular field analysis studies on agonists of melatonin sheep receptors

Conformational analysis was used to characterize the agonist pharmacophore for melatonin sheep brain receptor recognition and activation. The molecular geometry shared by all conformations of the selected active ligands was determined. Assuming that all the compounds interact at the same binding site at the receptor level, 2-iodomelatonin pharmacophoric conformation served as a template for the superimposition of 64 structurally heterogeneous agonists constituting the training set used to perform a three-dimensional quantitative structure-activity relationship study via the comparative molecular field analysis method. A statistically significant model was obtained for the totality of the compounds (n = 64, q2 = 0.62, N = 6, r2 = 0.96, s = 0.28, F = 249) with steric, electrostatic, and lipophilic relative contributions of 28%, 35%, and 37%, respectively. The predictive power of the proposed model was discerned by successfully testing the 78 agonist ligands constituting the test set. The model so obtained and validated brings important structural insights to aid the design of novel melatoninergic agonist ligands prior to their synthesis.

6-aminoalkyloxazolo[4,5-b]pyridin-2(3H)-ones: synthesis and evaluation of antinoceptive activity

Series of 6-aminoalkyloxazolo[4,5-b]pyridin-2(3H)-ones incorporating structural modifications both in the alkyl chain and basic amino moiety were tested for their analgesic efficacy and safety in mice and rats. Two of the synthesised compounds, 4a (3-methyl-6-[(4-phenyl-1-piperazinyl)methyl]oxazolo[4,5-b]pyridin-2(3H)-one) and 12a (3-methyl-6¿1-[2-(4-phenyl-1-piperazinyl)ethan-1-ol]¿oxazolo[4,5-b]pyridin- 2(3H)-one) were found to be more potent than aspirin with ED50 values of 26 (16.1-42.4) and 15.5 (11.4-21.2) mg/kg po (mouse, phenylquinone writhing test) respectively and 6 (3.1-9.8) and 5.5 (3.5-8.8) mg/kg po (rat, acetic acid writhing test). Compounds 4a and 12a proved to be potent nonopioid nonantiinflammatory analgesics but unfortunately have sedative properties at relatively low doses (respectively 64 and 16 mg/kg po, mice).

Substituted pyrido[3,2-b]oxazin-3(4H)-ones: synthesis and evaluation of antinociceptive activity

A new series of N-substituted pyrido[3,2-b]oxazinones has been synthesized, pharmacologically evaluated, and compared with acetyl salicylic acid. The compound with the maximal combination of safety and analgesic efficacy was 4-¿3-[4-(4-fluorophenyl-1-piperazinyl)propyl]¿-2H-pyrido[3,2-b]-1, 4-oxazin-3(4H)-one (6c) with ED50 values of 12.5 mg/kg po (mouse: phenylquinone writhing test) and 27.8 mg/kg po (rat: acetic acid writhing test), respectively. Compound 6c proved to be more active than aspirin with a safety index of 5.1.

N-substituted aminohydroxypyridines as potential non-opioid analgesic agents

A series of new N-substituted aminohydroxypyridines have been synthesized, pharmacologically evaluated and compared with their N-substituted oxazolopyridone analogs. The compound with the maximal combination of safety and analgesic efficacy was 3-[2-[4-(4-fluorophenyl)-1-piperazinyl]ethyl]amino-2-hydroxypyridine (compound 10a), with ED50 values 0.4 mg kg-1 po (mouse: phenylquinone writhing test) and 0.5 mg kg-1 po (rat: acetic acid writhing test). Compound 10a possesses a potent non-opioid antinociceptive activity with moderate anti-inflammatory properties.

Direct high-performance liquid chromatographic separation of the enantiomers of methoxy and hydroxy derivatives of 3,4-dihydro-3-(dipropylamino)-2H-1-benzopyrans with dopaminergic activity

The direct HPLC resolution of the enantiomers of methoxy and hydroxy derivatives of 3,4-dihydro-3-(dipropylamino)-2H-1-benzopyrans and of unsubstituted amino compounds was achieved using Chiralcel OD and/or Chiralpak AD stationary phases. The position of the substituent (methoxyl or hydroxyl) in the aromatic ring has a strong effect on the enantioselectivity. Circular dichroism spectra of the single enantiomers of one compound were measured.

N-substituted oxazolo[5,4-b]pyridin-2(1H)-ones: a new class of non-opiate antinociceptive agents

A series of 1-(aminoalkyl)- and 1-[(4-aryl-1-piperazinyl)alkyl]oxazolo[5,4-b]pyridin-2(1H)-one derivatives of oxazolo[5,4-b]pyridin-2(1H)-one, incorporating modifications to the length of the alkyl side chain and to the amino or 4-aryl-1-piperazinyl substituents, were tested for safety and analgesic efficacy in mice and rats. Some compounds with 4-(substituted or nonsubstituted phenyl)-1-piperazinyl substituents and a 3-4-carbon alkyl side chain had significantly greater analgesic activity than that of the oxazolo[4,5-b]pyridin-2(3H)-one analogs. To reduce the metabolic N-dealkylation of the piperazine observed in our previous work on oxazolo[4,5-b]-pyridin-2(3H)-ones, analogs of the most active compounds with steric hindrance on the alkyl side chain were prepared and tested. The compound with the maximal combination of safety and analgesic efficacy was 1-[[4-(4-fluorophenyl)-1-piperazinyl]propyl]oxazolo[5,4-b]pyridin- 2(1H)-one (compound 3b), with ED50 values of 5.6 mg/kg po (mouse, phenylquinone writhing test) and 0.5 mg/kg po (rat, acetic acid writhing test). Compound 3b is a potent, rapid-acting, non-opioid, nonantiinflammatory analgesic with low acute toxicity and sustained effect.

Preparation of 4,6-cyclo-hexopyranoses by palladium-mediated intramolecular cyclodehalogenation

4,6-Cyclo-4,6-dideoxy-hexapyronoses were obtained by palladium-mediated intramolecular cyclodehalogenation. Thus, methyl 2,3-di-O-acetyl-4,6-dideoxy-4,6-diiodo-beta-D-galactopyranoside (3) afforded methyl 2,3-di-O-acetyl-4,5-cyclo-4,6-dideoxy-beta-D-galactopyranoside (5) in 56% yield upon treatment with hydrogen in the presence of palladium-on-charcoal and diethylamine. The structure of 5 was proven by MS, NMR including NOE measurements, and by independent conversion of 4 to 5 by zinc-mediated Wurtz synthesis. Similarly, methyl 2,3-di-O-acetyl-4,6-cyclo-4,6-dideoxy-alpha-D-galactopyranoside (6) and O-(2,3,-di-O-acetyl-4,6-cyclo-4,6-dideoxy-alpha-D-galactopyranosyl)-(1-- >4)-1,2,3,6-tetra-O-acetyl-beta-D-glucopyranose (17) were obtained along with the respective 4,6-dideoxy analogues. Also methyl 2,3-di-O-acetyl-4,6-dideoxy-4,6-diiodo-beta-D-glucopyranoside (19) gave galacto-configured 5 stereoselectively.