The invention encompasses an active metabolite of the 18-membered macrocyclin antimicrobial agents, specifically, a metabolite of tiacumicin B and in certain embodiments, R-Tiacumicin B or and its related compounds. In particular, the invention encompasses a compound that acts asa potent antibiotic agent for the treatment of bacterial infections, specifically GI infections caused by toxin producing strains ofClostridium difficile(C. difficile)and Clostridium perfringents(C. perfringens).本發明係有關於18-員巨環狀抗微生物劑之活性代謝產物，更明確地，替庫辛(tiacumicin)B之代謝產物，且在特定實施例中，係有關於R-替庫辛B或其相關化合物。更詳細地，本發明係有關於可作為用於治療細菌感染，特別為藉困難性梭狀芽胞桿菌(Clostridium difficile(C. difficile))及產氣莢膜桿菌(Clostridium perfringents(C. perfringens))之產毒素菌株而引起之GI感染之有效力抗生素的化合物。
