1,5-naphthyridines. Synthesis of 7-chloro-4-(4-diethylamino-1-methylbutylamino)-2-methoxy-1,5-naphthyridine and related compounds

Zn-, Mg-, and Li-TMP Bases for the Successive Regioselective Metalations of the 1,5-Naphthyridine Scaffold (TMP=2,2,6,6-Tetramethylpiperidyl)

A set of successive regioselective metalations and functionalizations of the 1,5-naphthyridine scaffold are described. A combination of Zn-, Mg-, and Li-TMP (TMP=2,2,6,6-tetramethylpiperidyl) bases and the presence or absence of a Lewis acid (BF₃ ⋅OEt₂ ) allows the introduction of up to three substituents to the 1,5-naphthyridine core. Also, a novel "halogen dance" reaction was discovered upon metalation of an 8-iodo-2,4-trifunctionalized 1,5-naphthyridine allowing a fourth regioselective functionalization. Additionally, reactions leading to key 1,5-naphthyridines for the preparation of OLED materials and a potential antibacterial agent were performed.

Synthesis and evaluation of naphthyridine compounds as antimalarial agents

Primaquine is the drug of choice for the radical cure of Plasmodium vivax malaria, but possesses serious side effects. In this study novel primaquine analogues were designed and synthesized. Lower toxicity was achieved by reducing or eliminating the tendency of forming chemically reactive and toxic intermediates and metabolites. In vitro and in vivo studies found that synthesized compounds were less toxic than the parent compound primaquine, while preserving the desired antimalarial activity. Some of these compounds possess a therapeutic index over 10 times superior to that of the commonly used antimalarial drug chloroquine. These compounds, as well as the underlying design rationale, may find usefulness in the discovery and development of new antimalarial drugs.

Intramolecular Inverse-Electron-Demand Diels−Alder Reactions of Imidazoles with 1,2,4-Triazines: A New Route to 1,2,3,4-Tetrahydro-1,5-naphthyridines and Related Heterocycles

The intramolecular inverse-electron-demand Diels-Alder reaction between imidazoles and 1,2,4-triazines linked by a trimethylene tether from the imidazole N1 position to the triazine C3 proceed in excellent yields to produce 1,2,3,4-tetrahydro-1,5-naphthyridines. The reaction proceeds by a cycloaddition with subsequent loss of nitrogen, followed by a presumed stepwise loss of a nitrile. The analogous intramolecular cycloadditions employing a tetramethylene tether also proceeded to give 2,3,4,5-tetrahydro-1H-pyrido[3,2-b]azepines in acceptable yields. The reaction to produce the tetrahydro-1,5-naphthyridines can also be promoted with microwave irradiation.

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).

Antimalarial activity of Mannich bases derived from 4-(7'-bromo-1',5'-naphthyridin-4'-ylamino)phenol and 4-(7'-trifluoromethylquinolin-4'-ylamino)phenol against Plasmodium falciparum in vitro

Mono- and di-Mannich bases derived from 4-(7'-bromo-1',5'-naphthyridin-4'-ylamino)phenol and 4-(7'-trifluoromethylquinolin-4'-ylamino)phenol were assayed for antimalarial activity (using an in vitro radioisotopic technique) against two isolates of Plasmodium falciparum. Many from these two series of compounds had an IC50 value (concentration of compound causing 50% inhibition of 3H-hypoxanthine incorporation) comparable to or better than those of mefloquine and amodiaquine, for both a chloroquine-sensitive isolate (FCQ-27) and the chloroquine-resistant isolate (K1). At least one compound, 2,6-bis (piperidin-1''-ylmethyl)-4-(7'-trifluoromethylquinolin -4'-ylamino)phenol (TN112), showed significant superior activity to the three antimalarials chloroquine, mefloquine and amodiaquine against both isolates. (Statistically superior activity compared to these three antimalarials was found for TN112, except that against the K1 isolate its activity was just outside the range of significance relative to mefloquine.) Some of the 7-bromo-1,5-naphthyridine Mannich bases were appreciably less toxic in mice than amodiaquine.