In order to confer water solubility to the benzotetrazepinone ring system, the synthesis of 12 was undertaken. The design and synthesis of 12 were based upon previously established structural requirements for the stability of the 1, 2, 3, 5-tetrazepin-4-one ring system. Tetrazepinone 12 was extremely water soluble and was 10-fold more potent than its imidazo- 1, 2, 3, 5-tetrazin-4-one counterpart 1a, against the human MCF-7 breast cancer cell line.
