Abstract Three series of novel 8,9‐dihydro‐7 H ‐pyrimido[5,4‐ b ][1,4]diazepines, 4a – d , 5a – d , and 7a – d , were efficiently obtained in good yields using simple reaction methodologies. These pyrimidodiazepines were evaluated against 15 Mycobacterium spp. strains. Moderate activity in the inhibition of 13 microorganisms was obtained for the four compounds 4a , 5a , 5c , and 5d .