Synthesis and Antiplasmodial Evaluation of 4-Carboxamido- and 4-Alkoxy-2-Trichloromethyl Quinazolines.

From three previously identified antiplasmodial hit compounds (A-C) and inactive series (D), all based on a 2-trichloromethylquinazoline scaffold, we conducted a structure-activity relationship (SAR) study at position four of the quinazoline ring by synthesizing 42 novel derivatives bearing either a carboxamido- or an alkoxy-group, to identify antiplasmodial compounds and to enrich the knowledge about the 2-trichloromethylquinazoline antiplasmodial pharmacophore. All compounds were evaluated in vitro for their cytotoxicity towards the HepG2 cell line and their activity against the multiresistant K1 P. falciparum strain, using doxorubicin, chloroquine and doxycycline as reference drugs. Four hit-compounds (EC50 K1 P. falciparum ≤ 2 µM and SI ≥ 20) were identified among 4-carboxamido derivatives (2, 9, 16, and 24) and two among 4-alkoxy derivatives (41 and 44). Regarding the two most potent molecules (16 and 41), five derivatives without a 2-CCl3 group were prepared, evaluated, and appeared totally inactive (EC50 > 50 µM), showing that the 2-trichloromethyl group was mandatory for the antiplasmodial activity.

Discovery of new hit-molecules targeting Plasmodium falciparum through a global SAR study of the 4-substituted-2-trichloromethylquinazoline antiplasmodial scaffold.

From 4 antiplasmodial hit-molecules identified in 2-trichloromethylquinazoline series, we conducted a global Structure-Activity relationship (SAR) study involving 26 compounds and covering 5 molecular regions (I - V), aiming at defining the corresponding pharmacophore and identifying new bioactive derivatives. Thus, after studying the aniline moiety in detail, thienopyrimidine, quinoline and quinoxaline bio-isosters were synthesized and tested on the K1 multi-resistant P. falciparum strain, along with a cytotoxicity evaluation on the human HepG2 cell line, to define selectivity indecies. SARs first showed that thienopyrimidines and quinolines were globally more cytotoxic, while quinoxaline analogs appeared as active as- and less cytotoxic than their quinazoline counterparts. Such pharmacomodulation in quinoxaline series not only provided a new antiplasmodial reference hit-molecule (IC50 = 0.4 µM, selectivity index = 100), but also highlighted an active (IC50 = 0.4 µM) and quite selective (SI = 265) synthesis intermediate.

Looking for new antiplasmodial quinazolines: DMAP-catalyzed synthesis of 4-benzyloxy- and 4-aryloxy-2-trichloromethylquinazolines and their in vitro evaluation toward Plasmodium falciparum.

A DMAP catalyzed synthesis of new 4-benzyloxy- and 4-aryloxy-2-trichloromethylquinazolines was studied, in a view to react 4-chloroquinazolines with poorly nucleophilic alcohols such as benzylic alcohols, via a simple and cheap SNAr reaction approach. A fast (1 h) general operating procedure, affording good reaction yields, was achieved under microwave irradiation. Thus, a series of 35 molecules was obtained and evaluated in vitro on the K1 multi-resistant Plasmodium falciparum strain, in parallel with a cytotoxicity assessment on the human HepG2 cell line. 5 hit-molecules were identified, presenting both promising antiplasmodial activity (1.5 µM < IC50 < 2 µM) and low cytotoxicities (25 µM < CC50 < 45 µM). Apart for 2 molecules, the global series displayed a satisfying solubility in the aqueous biological media. Structure-activity relationships showed that the molecules presenting a benzyloxy moiety were less cytotoxic than the ones bearing a phenoxy moiety at position 4 of the quinazoline ring. It also appeared that the introduction of a heteroaryl moiety afforded inactive compounds. Finally, the most active and selective molecules (Selectivity Index = 22-27) were the ones presenting either an unsubstituted benzyloxy group or a phenoxy group, this last bearing a p-bromo or an o-acetyl substituent.

Preparation and antiprotozoal evaluation of promising ß-carboline alkaloids.

The synthesis of ß-carbolines and their in vitro antiplasmodial and antileishmanial activities were described herein. These molecules have also been studied concerning their in vitro cytotoxicity toward the human cell line THP1, in order to calculate their respective selectivity indexes (SI). Among the 20 tested molecules, four exhibited significant antiplasmodial activity on the W2 multi-resistant Plasmodium falciparum strain (0.7 < IC50 < 1.7 µM), in comparison with two references drugs (chloroquine and doxycycline), and a low cytotoxicity. These ß-carbolines were also evaluated concerning their in vitro antileshmanial activity on Leishmania donovani promastigotes, permitting to identify an antileshmanial hit compound, displaying quite promising activity (IC50 = 6.1 µM) in comparison with amphotericin B and pentamidine chosen as reference drugs. Finally, structure-activity relationships were discussed, pointing out that molecules presenting a para-substituted phenyl moiety at position 1 of the ß-carboline ring displayed the best biological profile.

Regioselective Suzuki-Miyaura reaction: application to the microwave-promoted synthesis of 4,7-diarylquinazolines.

New diarylquinazolines displaying pharmaceutical potential were synthesized in high yields from 4,7-dichloro-2-(2-methylprop-1-enyl)-6-nitroquinazoline by using microwave-promoted regioselective Suzuki-Miyaura cross-coupling reactions.

Original quinazoline derivatives displaying antiplasmodial properties.

The multistep synthesis of new quinazoline-derived molecules and their in vitro antiplasmodial evaluation on the W2 chloroquino-resistant Plasmodium falciparum strain is described herein. These molecules have also been studied concerning their in vitro cytotoxicity toward two human cell lines (K652 and HepG2) in order to calculate their respective selectivity indexes (S.I.). Among the fourteen tested molecules, two exhibited both significant antiplasmodial activity (IC(50)=0.95 and 1.3 microM) and low toxicity (IC(50)>100 or 125 microM), compared with two reference drugs: chloroquine and doxycycline. The structure activity relationships establish that the molecular scaffold which exerts the best profile is the 6-nitro-2-(tosylmethyl)-N-(3-substituted-phenyl)-quinazolin-4-amine. The hit molecules were finally investigated regarding their potential action toward two other protozoa, Leishmania donovani and Toxoplasma gondii, showing that these molecules display a selective antiplasmodial activity.

Synthesis and cytotoxicity evaluation of some benzimidazole-4,7-diones as bioreductive anticancer agents.

New benzimidazole-4,7-diones substituted at 2-position were synthesized via a microwave-assisted reaction using 2-chloromethyl-1,5,6-trimethyl-1H-benzimidazole-4,7-dione 5b as a key intermediate compound. Their cytotoxicity has been evaluated on colon, breast and lung cancer cell lines. The dimer 17 was shown to possess excellent cytotoxicity comparable to that of mitomycin C.

Synthesis of alpha,beta-unsaturated ketones as chalcone analogues via a S(RN)1 mechanism.

An electron-transfer chain reaction between 2-nitropropane anion and alpha-bromoketones derived from nitrobenzene and nitrothiophene was demonstrated by mechanistic study and a specific convenient synthetic protocol. Thus, 2-bromo-1-(5-nitrothiophen-2-yl)ethanone or 2-bromo-1-(4-nitrophenyl)ethanone were reacted with several cyclic nitronate anions to form alpha,beta-unsaturated ketones via a S(RN)1 mechanism. This new method can be used to synthesize a wide variety of chalcone analogues.