Tuberculosis (TB) has become an increasing problem since the emergence of human immunodeficiency virus and increasing appearance of drug-resistant strains. There is an urgent need to advance our knowledge and discover a new class of agents that are distinct than current therapies. Antimycobacterial activities of several 5-alkyl, 5-alkynyl, furanopyrimidines and related 2'-deoxynucleosides were investigated against Mycobacterium tuberculosis. Compounds with 5-arylalkynyl substituents (23-26, 33, 35) displayed potent in vitro antitubercular activity against Mycobacterium bovis and Mycobacterium tuberculosis. The in vivo activity of 5-(2-pyridylethynyl)-uracil (26) and its 2'-deoxycytidine analogue, 5-(2-pyridylethynyl)-2'-deoxycytidine (35), was assessed in BALB/c mice infected with M. tuberculosis (H37Ra). Both compounds 26 and 35 given at a dose of 50 mg/kg for 5 weeks showed promising in vivo efficacy in a mouse model, with the 2'-deoxycytidine derivative being more effective than the uracil analogue and a reference drug d-cycloserine. These data indicated that there is a significant potential in this class of compounds.