Synthesis of Novel Benzo[b][1,6]naphthyridine Derivatives and Investigation of Their Potential as Scaffolds of MAO Inhibitors

In this work, 2-alkyl-10-chloro-1,2,3,4-tetrahydrobenzo[b][1,6]naphthyridines were obtained and their reactivity was studied. Novel derivatives of the tricyclic scaffold, including 1-phenylethynyl (5), 1-indol-3-yl (8), and azocino[4,5-b]quinoline (10) derivatives, were synthesized and characterized herein for the first time. Among the newly synthesized derivatives, 5c-h proved to be MAO B inhibitors with potency in the low micromolar range. In particular, the 1-(2-(4-fluorophenyl)ethynyl) analog 5g achieved an IC₅₀ of 1.35 μM, a value close to that of the well-known MAO B inhibitor pargyline.

Synthesis of 5,6,7,8-Tetrahydro-1,6-naphthyridines and Related Heterocycles by Cobalt-Catalyzed [2 + 2 + 2] Cyclizations

[reaction: see text] Microwave-promoted, cobalt-catalyzed intramolecular [2 + 2 + 2] cyclizations of dialkynylnitriles successfully gave 5,6,7,8-tetrahydro-1,6-naphthyridines. The efficient synthesis of these relatively simple, yet rarely addressed heterocycles enabled the preparation of a collection of these compounds.

Synthesis of diazadibenzoperylenes and characterization of their structural, optical, redox, and coordination properties

Tetraphenoxy-substituted diazadibenzoperylenes 5a,b were synthesized from tetrachloroperylene tetracarboxylic acid bisanhydride 1 through imidization with benzylamine, nucleophilic displacement of the four chlorine atoms by phenolates, carbonyl group reduction by LiAlH(4)/AlCl(3), and subsequent Pd/C-promoted debenzylation-dehydrogenation. The structural properties of these extended diazaarenes are discussed on the basis of a X-ray crystal structure of the N,N'-dibutylated diazadibenzoperylenium dication 6, which revealed a 25 degrees twist of the central six-membered ring leading to an atropisomeric pi-conjugated backbone. The chromophoric systems of 5 and 6 were characterized by optical absorption and fluorescence spectroscopy, which revealed an intense fluorescence with a quantum yield of 75% for 5 and 50% for 6. Cyclic voltammetry showed reversible oxidation and reduction waves for 6, whereas the oxidation of 5 afforded the irreversible deposition of a conductive film on the electrode surface. Finally, the potential use of ligands 5 in supramolecular chemistry has been evaluated by complexation experiments with carboxylic acids and zinc tetraphenylporphyrin (ZnTPP).

Synthesis and SAR of 5-, 6-, 7- and 8-aza analogues of 3-aryl-4-hydroxyquinolin-2(1H)-one as NMDA/glycine site antagonists

A series of 5-, 6-, 7- and 8-aza analogues of 3-aryl-4-hydroxyquinolin-2(1H)-one was synthesized and assayed as NMDA/glycine receptor antagonists. The in vitro potency of these antagonists was determined by displacement of the glycine site radioligand [(3)H]5,7-dicholorokynurenic acid ([(3)H]DCKA) in rat brain cortical membranes. Selected compounds were also tested for functional antagonism using electrophysiological assays in Xenopus oocytes expressing cloned NMDA receptor (NR) 1A/2C subunits. Among the 5-, 6-, 7-, and 8-aza-3-aryl-4-hydroxyquinoline-2(1H)-ones investigated, 5-aza-7-chloro-4-hydroxy-3-(3-phenoxyphenyl)quinolin-2-(1H)-one (13i) is the most potent antagonist, having an IC(50) value of 110 nM in [(3)H]DCKA binding and a K(b) of 11 nM in the electrophysiology assay. Compound 13i is also an active anticonvulsant when administered systemically in the mouse maximum electroshock-induced seizure test (ED(50)=2.3mg/kg, IP).

Inhibition of wheat embryo calcium-dependent protein kinase by acridines and azaacridines

The inhibition of wheat Ca(2+)-dependent protein kinase (CDPK) by substituted acridines and substituted 5-, 6-, 7- and 8-azaacridines (5-AA, 6-AA, 7-AA and 8-AA) was examined. Of a total of 71 substituted acridines and azaacridines examined, only 20 have IC50 values for wheat CDPK of less than 200 microM. Of these, effective compounds all have neutral or basic 4-substituents, except for 2,7-dibromo-4-carboxy-5-AAO (IC50 73 microM), the carboxymethyl ester of which is a much better inhibitor (IC50 20 microM). There is a large aza position effect so that various 4-substituted azaacridines can be either very active or very poor inhibitors depending upon the azaacridine nucleus substituted. One of the most potent inhibitors found is the 8-AA 4-N-(2-dimethylaminoethyl)carboxamide (4-P) derivative (IC50 1.5 microM), but the corresponding 4-substituted acridine analogue is a very poor inhibitor. Other potent inhibitors found include 1-nitro-4-P-8-AA (IC50 4 microM) and 7-bromo-4-methyl-5-AA (IC50 0.7 microM). These potent and relatively specific CDPK inhibitors may be useful in obtaining evidence for CDPK involvement in plant cell responses to specific signals.