Design, Synthesis And Biological Evaluation Of Novel Antituberculosis Derivatives Targeting To ATP Synthase

Tuberculosis (TB) caused by Mycobacterium tuberculosis (MTB) is a worldwide disease with high infection and high mortality. Approximately one-third of world's population has infected MTB and two million people of them died annually. Currently available TB drugs are classified as first-line and second-line drugs. First-line drugs contain Isoniazid, Pyrazinamide, Ethambutol, Rifampin and Streptomycin while second-line drugs include Amikacin, Ofloxacin, Ciprofloxacin, Levofloxacin, Ethionamide, Prothionamide, Lamprene and so on. These antituberculosis drugs has limited the spread of tuberculosis, but the situations are still serious because of long treatment making patients difficult to complete the cure and the emergence of multidrug resistant TB (MDR-TB) and newly developed extensively drug resistant TB (XDR-TB) which can't be cured by currently available TB drugs. Besides, the reasons of increase of global population mobility and the population infected HIV and no any novel antituberculosis drugs developed in last 40 years enhance the worried situation. The worldwide institutions of dedicating to TB drugs research did their best to convert this situation and encouragingly found some new TB drugs which have already been in their clinical trials or preclinical trials. These drugs include moxifloxacin, Gatifloxacin, Rifapentine, PA-824, OPC-67683, SQ109, TMC207 and so on. The advantages of these drugs exhibiting excellent activity, novel structures and targets and lower toxicity give hopes for global therapy and prevention of TB.Adenosine triphosphate (ATP) is a chief high-energy compound in organism. It is hydrolyzed to provide energy for vital movements such as cell division, muscular movement, neural conduction, active transport and so forth. ATP synthase is a key enzyme in organism where ATP can be synthesized and hydrolyzed. ATP synthase is generally located in the mitochondrial inner membranes of eukaryotic cells, bacterial plasma membranes and chloroplast thylakoid membranes. ATP synthase can be divided into F, A, V, P types and F-type ATPase is most important. F-type ATPase has a lipophilic intramembrane portion (F0) and an ATP-binding region (F1) that extends into the cytoplasm. F0 portion is consisted of a, b2, and c9-12 subunits while F1 portion is consisted ofα3,β3,ε,γandδsubunits. Once the concentration of ATP intramembrane shrinks, ATP synthase can provide ATP while c subunits act as an ionic turbomachine. Once the concentration of ATP intramembrane advanced, ATP synthase can hydrolyze ATP while c subunits act as an ionic pump. TMC207 works targeting to c subunits of ATP synthase of mycobacteria and inhibiting the synthesis of ATP.TMC207, a type of novel diarylquinoline anti-tuberculosis drugs, has been in clinical trial II. It exhibits excellent activity, high selectivity for mycobacteria, long term of drug potency and no obvious toxicity. The combination of TMC207 with current TB drugs can enhance the activity and shorten the treatment cycle. Much more importantly, TMC207 can exhibit superior activity against MDR-TB and XDR-TB with no cross-resistance to current TB drugs. It is contributed to its unique mechanism of targeting to ATP synthase of mycobacteria. TMC207 exhibits inhibitory and bactericidal activity via inhibiting the synthesis of ATP and sequentially disturbing and interrupting energy metabolism of bacteria.The studies of structure-activity relationships of diarylquinoline antituberculosis drugs containing TMC207 suggest that the hydroxy group of the tertiary alcohol and the dimethyl amino terminus are essential functional groups for potent antituberculosis activity and the three carbon atom distance of the two functional groups is best. They also maintain that three aryl-rings of diarylquinoline drugs have a large spatial structure and are helpful for selectivity. Thus, we have designed and synthesized a series of triaryl-substituted-4-(amino)butan-2-ol derivatives to further investigate the influence of antituberculosis activity with the substituent groups to aryl-rings and the nitrogen in quinoline-ring.We improved the patented route of synthesis of TMC207. We started the preparation with 3-phenylpropionic acid reacted with 4-bromaniline subsequently via ring closure by Vilsmeier-Haauc reaction and nucleophilic substituted reaction with sodium methylate leading to intermediate 3-benzyl-6-bromo-2-methoxyquinoline. The intermediate was reacted with mannich base 3-(dimethylamino)-1-(naphthalen-1-yl) propan-1-one which was freshly provided. The reaction product was purified to get two pairs of enantiomers, (1R/2S, 1S/2R) enantiomer which contains TMC207 and (1R/2R, 1S/2S) enantiomer, acting as positive control in the next in vitro trial.In addition, in the preparation of target compounds triaryldimethyl aminobutan-2-ol derivatives, 3-hydroxy-2-naphthoic acid as a raw material undergone the reactions the bromo-substituted reaction with bromine, debromination with powdery tin, Methylation with dimethyl sulfate, reduction with lithium aluminium hydride and oxidation with manganese dioxide to get substituted naphthoic aldehyde. The naphthoic aldehydes were reacted with different grignard reagents prepared from various substituted bromobenzene and then reduction with the mixture of sodium borohydride and aluminum trichloride to get intermediates substituted diaryl methane. These intermediates were reacted with mannich base 3-(dimethylamino)-1- (naphthalen-1-yl)propan-1-one which was freshly provided. The reaction products were purified to afford 38 target compounds. All the target compounds are reported for the first time and confirmed by 1H-NMR and MS. Configuration of partial compounds were comfirmed via single-crystal X-ray study.Minimum inhibitory concentration (MIC90) of all target compounds against M. tuberculosis H37Rv were evaluated with the method Microplate Alamar Blue Assay (MABA). The activities of enantiomers of RS/SR are all better than enantiomers of RR/SS. Compounds TM-08, TM-12, TM-21, TM-26, TM-29, TM-37 and TM-39 show the similar activities compared with positive control compound TM-01. Especially compounds TM-15, TM-17, TM-20, TM-24, TM-31 and TM-35 surpass TM-01. Preliminary assessment of acute toxicity with compounds TM-04, TM-08 and TM-12 in mice suggests that there was no obvious toxicity in mice.The studies of structure-activity relationships suggested that the nitrogen in quinoline-ring of TMC207 represent of diarylquinolines is not essential for activity. In triaryl-substituted-4-(amino)butan-2-ol derivatives, bromine to 7-position of naphthalene ring might be an essential functional group, and so did methoxy to 3- position of naphthalene ring acting as receptor of hydrogen bond while hydroxyl acting as donor of hydrogen bond strongly decreased the activity. Halogen and methyl of phenyl to 1-position or 2-position of compounds didn't give much more influence for the activity. The salification of compounds might enhance the actibities.To conclude, the structural reform of diarylquinolines is successful and the Summary of structure-activity relationships of compounds will provide valuable references for next research of antituberculosis.