Antibacterial activity of dihydro-1,3-oxazine derivatives condensed with aromatic rings in positions 5,6.

1. The antibacterial activity in vitro of dihydro-1,3-oxazine derivatives with aromatic rings condensed in positions 5, 6 was examined.2. Of more than thirty compounds examined, two (T 615 and T 638) showed marked activity against various strains of Mycobacterium tuberculosis at concentrations below 2 mug/ml.3. These two compounds also showed marked activity against Escherichia coli, Clostridium pneumoniae and Salmonella typhi.4. Both showed marked activity in vivo against tuberculosis produced in mice and guinea-pigs by various strains of Mycobacterium such as human strain ;Sz', bovine ;An 5' and H37Rv non-resistant and resistant to isonicotinic acid hydrazide (INH), streptomycin (SM) and p-aminosalicylic acid (PAS).