Symmetrical and unsymmetrical analogues of the antimycobacterial agent isoxyl-have been synthesized and tested against Mycobacterium tuberculosis H37Rv and Mycobacterium bovis BCG, some showing an increased bactericidal effect. In particular, compounds 1-(pn- butylphenyl)-3-(4-propoxy-phenyl) thiourea (10) and 1-(pn-butylphenyl)-3-(4-n-butoxy- phenyl) thiourea (11) showed an approximate 10-fold increase in in vitro potency ...