Tuberculosis (TB) is a contagious airborne disease caused by a deadly bacterium pathogen called mycobacterium tuberculosis. TB is the second leading infectious disease in the world and remains one of the biggest public health problems in the 21st century. According to the World Health Organization (WHO), it is estimated that about a third of the world's population are latently infected with TB bacteria, almost 2 million people die from this deadly disease annually, and the number of infected cases are still rising rapidly because of human immunodeficiency virus (HIV) coinfection, multi-drug and extensively drug resistant tuberculosis. The common challenges and problems regarding tuberculosis treating regimens include its latency, long treating regimen, HIV coinfection, and emerging drug resistance. Notably, no TB specific drugs have been discovered since the introduction of Rifampin 40 years ago, therefore, there is an urgent need for TB drug research community to develop fast acting and potent antituberculosis agents with new mechanism of action and less cross resistance properties. Historically, the majority of antimicrobial agents including TB drugs originate from natural products with the remaining derived from synthetic small molecules. In this proposal, we will apply HTS hits guided and natural product inspired approaches to develop novel antituberculosis agents. The first specific aim focuses on further optimization and development of synthetic antitubercular piperidinol derivatives, the design driver toward a second generation series is to focus on enhancing the desired activity, lowering the toxicity, and thus improving overall therapeutic index. The approaches include: (i) Systematic optimization and examination of SAR based on first generation piperidinol derivatives;(ii) Several new series of piperidinol derivatives will also be explored in an effort to identify new chemotypes or scaffolds for further evaluation and development. The second specific aim is to design and synthesize natural Engelhardione analogues for antituberculosis screening. Engelhardione, a macrocyclic diphenyl ether haptanoid, was reported to show potent in vitro antituberculosis activity against Mycobacterium tuberculosis strain H37Rv (MIC = 0.2 <g/mL). Despite its potent activity, there is no reported synthesis of Engelhardione and antituberculosis evaluation of its analogues in the literature, this lack of development prompts us to direct medicinal chemistry effort in this application. In this aim, we propose to first develop a feasible synthesis toward Engelhardione by adapting existing synthetic schemes, the second subaim is to design and synthesize its analogues and derivatives for antituberculosis testing in an effort to identify more potent and less toxic Engelhardione experimental candidates. PUBLIC HEALTH RELEVANCE: Due to the emergence and evolution of drug resistant mycobacterium tuberculosis, there is an urgent need to discover new chemotype TB drugs with novel mechanism of action and low toxic properties. In this application, by employing HTS hits guided and natural product inspired approaches we propose to optimize and develop synthetic piperidinol derivatives and natural Engelhardione analogues as novel antituberculosis agents. The results of the proposed research will generate significant biological data and gain important understanding regarding novel piperidinol and Engelhardione antituberculosis agents, after this study, we hope to identify promising candidates with potent in vitro activity and low toxicity for subsequent in vivo efficacy and toxicity studies. Furthermore, development of these novel antituberculosis agents has the potential to overcome the cross resistance with current clinically used TB drugs and to shorten current TB treating regimen.