Search

A new group of 5-(alkylamino)-9-isopropyl[1,2,4]triazolo[4,3-a][1,8]naphthyridine derivatives bearing a CONHR group at the 6-position (1c-g), designed to obtain new effective analgesic and/or anti-inflammatory agents, were synthesized and tested along with three new 9-alkyl-5-(4-alkyl-1-piperazinyl)-N,N-diethyl [1,2,4]triazolo[4,3-a][1,8]naphthyridine-6-carboxamides (2b-d). Besides, a new class of analogues of compounds 1 and 2, bearing a Mannich base moiety at the 9-position (12a-d), as well as the novel N,N-diethyl-5-(isobutylamino)-8-methyl-10-oxo-10H-pyrimido[1,2-a][1,8]naphthyridine-6-carboxamide (15) were prepared and tested. Compounds 1c-g exhibited very interesting anti-inflammatory properties in rats, whereas compounds 2b-d and 15 proved to be endowed with prevalent analgesic activity frequently associated with sedative effects in mice. On the contrary, the Mannich bases 12a-d resulted inactive. The most effective (80% inhibition of oedema) and potent (threshold dose 1.6 mg kg(-1) with 31% inhibition of oedema) anti-inflammatory compound 1d did not show gastrolesive effects following 100 mg kg(-1) oral administration in rats., (Copyright © 2014 Elsevier Masson SAS. All rights reserved.)

On the basis of the very interesting pharmacological properties shown by the 5-amino[1,2,4]triazolo[4,3-a][1,8]naphthyridine-6-carboxamide derivatives 1, previously described by us, we have now prepared the 5-aminoimidazo[1,2-a][1,8]naphthyridine-6-carboxamide derivatives 2a-o (a new structural class) whose tricyclic system is isosteric to that of compounds 1. Both compounds 2 and some new properly substituted compounds 1 (1f-k) now synthesized were tested in vivo for their analgesic and anti-inflammatory activities: on the whole, compounds 2 showed notable analgesic properties, whereas many compounds 1 exhibited a very potent anti-inflammatory activity, coupled to scarce analgesic activity. All the effective compounds proved to be completely devoid of acute gastrolesivity (gastric damage) in rats (at the 200 mg kg(-1) oral dose)., (Copyright 2009 Elsevier Masson SAS. All rights reserved.)

The [1,2,4]triazolo[4,3-a][1,8]naphthyridine-6-carboxamide derivatives 5-amino (2) or 5-alkoxy (3) substituted and the 5-amino[1,2,4]triazolo[4,3-a]quinoline-4-carboxamide derivatives (4), designed to obtain new effective analgesic and/or anti-inflammatory agents were synthesized. Ten compounds 2 and 4 showed an interesting analgesic activity: the most potent ones are 2j (36% inhibition, P<0.05) and 4b (77% inhibition, P<0.01) at 6.25 and 25 mg kg(-1) doses, respectively. Compounds 2i-l and 4c showed notable anti-inflammatory properties: the most potent ones are 2i (68% inhibition, P<0.01) and 2l (42% inhibition, P<0.05) at 12.5 and 6.25 mg kg(-1) doses, respectively. The replacement in compounds 2 of the N-substituted 5-amino substituents with similar alkoxy groups usually afforded less active compounds 3.

On the basis of the good anti-inflammatory properties shown by the 9-alkyl-N,N-dialkyl-5-(alkylamino)[1,2,4]triazolo[4,3-a][1,8]naphthyridine-6-carboxamides 1, a series of analogues of such compounds, in which the 9-alkyl substituent was replaced by an ester or amide group (compounds 3a-i), was prepared and tested (inhibition of carrageenan-induced paw edema in the rat). Also two 5-(N-alkyl,N-acylamino) derivatives (compounds 4a,b) were synthesized and evaluated for the same purpose. Even though the general trend for these new [1,2,4]triazolo[4,3-a][1,8]naphthyridine derivatives was a decrease in activity compared with compounds 1, some of the new synthesized compounds exhibited still good anti-inflammatory properties.

Most N,N-disubstituted 5-amino-N,N-diethyl-9-isopropyl [1,2,4]triazolo[4,3-a] [1,8]naphthyridine-6-carboxamides 9 (compounds 9a, c-i) and the N-monosubstituted one 8c were obtained by treating with excess amine the corresponding 5-chloroderivative 7a, which was in turn prepared by cyclocondensation of the 2,4-dichloro-N,N-diethyl-1,8-naphthyridine-3-carboxamide (4a) with isobutyrohydrazide. Compounds 8a,b and 9b,j-m were obtained according with the methods shown in Scheme 1. The above now synthesized compounds, along with the previously described 8d and 8e, were tested for their anti-inflammatory, analgesic and antipyretic properties, and most compounds also for their effect on spontaneous mice locomotor activity and their acute gastrolesivity in rats. Several compounds showed potent anti-inflammatory and/or analgesic activities, and all the compounds tested proved to be completely lacking in acute gastrolesivity. In many cases compounds 8 and 9 produced hypothermic effect, usually at high doses. On the whole, the N-monosubstituted 5-aminoderivatives 8 appeared to be more potent anti-inflammatory agents than the corresponding N,N-disubstituted 9, whereas these latter compounds exhibited higher analgesic activity.