Design of novel camphane-based derivatives with antimycobacterial activity

QSAR-driven design, synthesis and discovery of potent chalcone derivatives with antitubercular activity

New anti-tuberculosis (anti-TB) drugs are urgently needed to battle drug-resistant Mycobacterium tuberculosis strains and to shorten the current 6-12-month treatment regimen. In this work, we have continued the efforts to develop chalcone-based anti-TB compounds by using an in silico design and QSAR-driven approach. Initially, we developed SAR rules and binary QSAR models using literature data for targeted design of new heteroaryl chalcone compounds with anti-TB activity. Using these models, we prioritized 33 compounds for synthesis and biological evaluation. As a result, 10 heteroaryl chalcone compounds (4, 8, 9, 11, 13, 17-20, and 23) were found to exhibit nanomolar activity against replicating mycobacteria, low micromolar activity against nonreplicating bacteria, and nanomolar and micromolar against rifampin (RMP) and isoniazid (INH) monoresistant strains (rRMP and rINH) (<1 μM and <10 μM, respectively). The series also show low activity against commensal bacteria and generally show good selectivity toward M. tuberculosis, with very low cytotoxicity against Vero cells (SI = 11-545). Our results suggest that our designed heteroaryl chalcone compounds, due to their high potency and selectivity, are promising anti-TB agents.

Crystal structures of two (±)-exo-N-isobornyl-acetamides

The title compounds consist of a 1,7,7-tri­methylbi­cyclo­[2.2.1]heptane (bornane or camphane) skeleton which is decorated with acetamide for (±)-(1) and chloro­acetamide for (±)-(2), functionalities. In the crystals of both compounds, mol­ecules are linked via N—H⋯O hydrogen bonds, reinforced by C—H⋯O contacts, forming chains propagating along the a axis.

The title compounds consist of a bornane skeleton with attached acetamide, C₁₂H₂₁NO (±)-(1) {systematic name: (±)-N-[(1RS,2RS,4RS)-1,7,7-tri­methylbi­cyclo­[2.2.1]heptan-2-yl]acetamide}, and chloro­acetamide, C₁₂H₂₀ClNO (±)-(2) {systematic name: (±)-2-chloro-N-[(1RS,2RS,4RS)-1,7,7-tri­methylbi­cyclo­[2.2.1]heptan-2-yl]­acetamide}, functionalities to the 2-exo-position. The crystal structure of the first monoclinic polymorph of (±)-(1) has been reported previously [Ung et al. (2014 ▸). Monatsh. Chem.145, 983–992]. Compound (±)-(1) crystallizes in the space group P2₁/n with two independent mol­ecules in the asymmetric unit, in contrast to the above-mentioned polymorph which crystallized in the space group C2/c with one mol­ecule in the asymmetric unit. In the title compounds, the bicyclic bornane moieties have normal geometries. In the crystals of both compounds, mol­ecules are linked by N—H⋯O hydrogen bonds, reinforced by C—H⋯O contacts, forming trans-amide chains propagating along the a-axis direction. In the case of compound (±)-(1), neighbouring chains are linked by further C—H⋯O contacts, forming double-chain ribbons along [100].