Mario Di Braccio

1,8-Naphthyridines IV. 9-Substituted N,N-dialkyl-5-(alkylamino or cycloalkylamino) [1,2,4]triazolo[4,3-a][1,8]naphthyridine-6-carboxamides, new compounds with anti-aggressive and potent anti-inflammatory activities

The title compounds (8) were synthesized through the cyclocondensation of the corresponding N-substituted 4-amino-2-chloro-1,8-naphthyridine-3-carboxamides (4) with the proper hydrazides, in order to evaluate their anti-inflammatory and anti-aggressive properties. Several compounds 8 exhibited high anti-inflammatory activity (carrageenin-induced paw edema assay in the rat) along with appreciable anti-aggressive properties (isolation-induced aggressiveness test in mice). With respect to anti-inflammatory activity, the most active compounds (8n and 8c) produced a 61% edema inhibition at the 25 mg/kg dose, and 50 or 35% inhibition, respectively, at the 12.5 mg/kg dose. The structure-activity relationships are discussed.

1,5-Benzodiazepines. Part XII. Synthesis and biological evaluation of tricyclic and tetracyclic 1,5-benzodiazepine derivatives as nevirapine analogues

A number of properly substituted 5H-pyrimido[4,5-b][1,5]benzodiazepines (2) and pyrazolo[3,4-b][1,5]benzodiazepines (3 and 4), as well as compounds 5-7, which are derivatives of new tetracyclic systems, were prepared as nevirapine analogues through multistep synthetic routes. The cytotoxic and anti-HIV-1 properties of compounds 2-7 were evaluated in cell-based assays, together with their inhibitory activity against the HIV-1 recombinant reverse transcriptase (rRT) in enzyme assays. The modifications introduced into nevirapine heterocyclic skeleton proved to have a negative effect for the anti-HIV-1 activity. It is worth noting that some of the new derivatives proved to be cytotoxic in the low micromolar range.

Coumarin, chromone, and 4(3H)-pyrimidinone novel bicyclic and tricyclic derivatives as antiplatelet agents: synthesis, biological evaluation, and comparative molecular field analysis.

As a further part of our chemical and biological studies in this field, we describe the multistep preparations of the properly substituted 2-(1-piperazinyl)chromone 1b, 4-(1-piperazinyl)coumarins 5c-h, their linear benzo-fused analogues 4a,b and 8a,b, bicyclic (15e-g) and tricyclic (15h,i) fused derivatives of 6-(1-piperazinyl)pyrimidin-4(3H)-one, and of the 4H-pyrido[1,2-a]pyrimidine derivatives 9b,c. The in vitro evaluation of their inhibitory properties towards human platelet aggregation induced in platelet-rich plasma by ADP, collagen, or the Ca (2+)ionophore A23187 showed the high activity of compounds 5d-g and 15f,g,i, among which the coumarins 5g and 5d proved to be, in that order, the most effective in vitro antiplatelet agents until now synthesized by us. Thus, in order to consider also the 4-aminocoumarin structural class, we developed a new statistically significant 3-D QSAR model, more general than the one previously obtained, through a further CoMFA study based on the antiplatelet activity data and molecular steric and electrostatic potentials of both the previously studied and herein described compounds.

1,5-benzodiazepines. Part XIII. Substituted 4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5-amines and 4H-imidazo[1,2-a][1,5]benzodiazepin-5-amines as analgesic, anti-inflammatory and/or antipyretic agents with low acute toxicity.

The reaction of proper N,N-dialkyl-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepin-5-amines (1) with N-chlorosuccinimide afforded their 4-chloroderivatives 3 which in turn were treated with cyclic amines to give the corresponding 4,5-diaminoderivatives 4. The N,N-dialkyl-4H-imidazo[1,2-a][1,5]benzodiazepin-5-amines (5) were prepared starting from suitable 4-(dialkylamino)-1,3-dihydro-2H-1,5-benzodiazepin-2-ones (8), through multistep synthetic routes. At the 200 mg kg(-1) os dose, some compounds 3 and 4 showed notable analgesic or anti-inflammatory activity but no antipyretic properties, whereas the 5-(dibutylamino) derivatives 5b and 5f proved to be significantly endowed with all these activities. Almost all the compounds 3, 4 and 5 did not show acute toxicity in mice up to 800 mg kg(-1) os dose.

Synthesis, antiplatelet activity and comparative molecular field analysis of substituted 2-amino-4H-pyrido[1,2-a]pyrimidin-4-ones, their congeners and isosteric analogues

2-(1-Piperazinyl)-4H-pyrido[1,2-a]pyrimidin-4-one (5a) is a recently described in vitro inhibitor of human platelet aggregation which specifically inhibits the activity of high affinity cAMP phosphodiesterase. A number of substitution derivatives, isosteres, and analogues of 5a were now synthesized and tested in vitro for their inhibitory activity on human platelet aggregation induced in platelet-rich plasma by ADP, collagen, or the Ca2+ ionophore A23187. Among the most effective compounds, the 6-methyl, 8-methyl and 6,8-dimethyl derivatives of 5a resulted nearly as active as the lead when platelet aggregation was induced by ADP or A23187, but less active when collagen was the inducer. On the basis of present results and those previously obtained by us in this and 2-aminochromone structural fields, we have developed a statistically significant 3-D QSAR model, using comparative molecular field analysis (CoMFA), describing the variation of the antiplatelet activity in terms of molecular steric and electrostatic potential changes.

Synthesis and anti-platelet activity of some 2-(dialkylamino)chromones

Substituted 2-(diethylamino) or 2-(ethylamino)chromones 5a—g were obtained from the reaction of suitable phenols with the reagent ethyl N,N-diethyl- or N-ethylmalonamate/POCl3 (2a or 2b). The above compounds, together with other N-substituted 2-aminochromones, either prepared from related chromones by simple reactions (5h—k) or previously obtained by us (5l—w), were tested in vitro for their inhibitory activities against human platelet aggregation induced by collagen, ADP and arachidonic acid. Many compounds showed activity and some were more active than acetylsalicylic acid in the tests with ADP and arachidonic acid. When the 2-amino substituent of tested chromones was a diethylamino group, the highest activity was found. The presence in position 7 of electron releasing substituents (OH, OCH3, CH3) led to an increase of activity, whereas a decrease occurred when an electron withdrawing substituent was present in position 3 (NO2) or 6 (NO2, Cl).

Pyran derivatives: Part XXI. Antiproliferative and cytotoxic properties of novel N-substituted 4-aminocoumarins, their benzo-fused derivatives, and some related 2-aminochromones

The N-substituted tricyclic 2-aminochromone derivatives 1a, 2a, and 2b were obtained by treating the corresponding (methylthio) or (methylsulfinyl) derivatives 10, 11, or 12, respectively, with an excess of the proper amines. Compound 2c was synthesized through the reaction of 2-naphthol with the ethyl N,N-diphenylmalonamate/POCl(3) reagent 14. The N-substituted 4-aminocoumarin bicyclic and tricyclic derivatives 5-8 were prepared by treating the corresponding chloro derivatives with the excess suitable amines. Compounds 1, 2, 5-8 were tested in vitro for their antiproliferative activity (DNA synthesis inhibition in Ehrlich cells) and cytotoxicity (MTT test in HeLa cells). The inhibitory properties of three selected compounds (5c, 5e, 7c) on protein and RNA syntheses in Ehrlich cells were also evaluated. Among the 27 compounds tested, 10 4-aminocoumarin derivatives (5-8) and two 2-aminochromone derivatives (1a and 2a) showed an appreciable antiproliferative activity (IC(50) range: 1.74-13.8 microM), whereas only four compounds 5-8 exhibited a comparable cytotoxic activity (IC(50) range: 4.95-12.9 microM).

1,8-Naphthyridines VIII. Novel 5-aminoimidazo[1,2-a] [1,8]naphthyridine-6-carboxamide and 5-amino[1,2,4]triazolo[4,3-a] [1,8]naphthyridine-6-carboxamide derivatives showing potent analgesic or anti-inflammatory activity, respectively, and completely devoid of acute gastrolesivity

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).

Effect of 2-(1-piperazinyl)-4H-pyrido[1,2-a]pyrimidin-4-one (AP155) on human platelets in vitro.

The effect on human platelets of 2-(1-piperazinyl)-4H-pyrido[1,2-a]pyrimi din-4-one (AP155) was tested in vitro by measuring cyclic adenosine monophosphate (cAMP) level, cytosolic Ca++, [(125I)]fibrinogen binding as well as aggregation induced by several agonists. AP155 dose-dependently inhibited aggregation both in platelet rich plasma (PRP) and in washed platelets (WP), exerting its maximal power in the presence of collagen, ADP and platelet activating factor (PAF). It specifically inhibited the activity of cAMP high affinity phosphodiesterase (PDE), resulting in a sufficient increase in cAMP levels to activate cAMP-dependent protein kinase. AP155 was able to inhibit aggregation, the increase in cytosolic Ca++ induced by thrombin, and fibrinogen binding to ADP or thrombin-stimulated platelets. Thus, this new pyridopyrimidine derivative exerts its antiplatelet activity by increasing cAMP intracellular concentration.

Fine molecular tuning at position 4 of 2H-chromen-2-one derivatives in the search of potent and selective monoamine oxidase B inhibitors

The effects on the inhibition potencies of monoamine oxidase isoforms A (MAO-A) and B (MAO-B) depending upon changes in the physicochemical properties (size, shape, H-bonding, lipophilicity, etc.) of substituents at the C4 position of 2H-chromen-2-one derivatives were extensively investigated, and the results significantly added to our knowledge on this class of MAO inhibitors. All the 67 examined compounds showed high MAO-B selectivity, some of them achieving potency in the low nanomolar range. In particular, the 7-metachlorobenzyloxy-4-oxyacetamido-2H-chromen-2-one (entry 62) showed single digit nanomolar MAO-B potency (IC₅₀ = 3.1 nM) and high selectivity over the MAO-A isoform (selectivity ratio = 7244). The great variety of the investigated substituents at C4 of the 2H-chromen-2-one nucleus, combined with binding models generated from docking studies carried out on selected compounds, allowed us to shed light on the main molecular requirements for potent and selective MAO-B inhibition, highlighting the dominant role of the steric effects. Interestingly, many of the designed substituents could be metabolically related to each other (e.g., CH₃/CH₂OH/CHO/COOH; NH₂/NHCH₃, NHAc), and therefore the results obtained may help in predicting the in vivo activity of some putative metabolites of lead MAO-B inhibitors.