Cephalosporins. III. 7-(o-Aminomethylphenylacetamido)cephalosporanic acids with bicyclic heteroaromatics in the C-3 side chain was written by Naito, Takayuki;Okumura, Jun;Kamachi, Hajime;Hoshi, Hideaki;Kawaguchi, Hiroshi. And the article was included in Journal of Antibiotics in 1977.Electric Literature of C5H3ClN4O This article mentions the following:
Cephalosporins I (R = bicyclic N heterocycle) (10 compounds) were prepared Thus, 7-aminocephalosporanic acid was treated with 6-tetrazolo[1,5-b]pyridazinethiol, followed by 2-Me3CO2CNHCH2C6H4CH2CO2C6H3(NO2)2-2,4 and deblocked to give 74% I (R = 6-tetrazolo[1,5-b]pyridazinyl). This compound had min. inhibitory concentrations against Staphylococcus aureus Smith 0.1 and Escherichia coli NIHJ 0.4 μg/mL. In the experiment, the researchers used many compounds, for example, 6-Chloro-[1,2,4]triazolo[4,3-b]pyridazin-3(2H)-one (cas: 33050-32-7Electric Literature of C5H3ClN4O).
6-Chloro-[1,2,4]triazolo[4,3-b]pyridazin-3(2H)-one (cas: 33050-32-7) belongs to pyridazine derivatives. Pyridazines are rare in nature, possibly reflecting the scarcity of naturally occurring hydrazines, common building blocks for the synthesis of these heterocycles. Pyridazine can act as a hydrogen bond acceptor to improve the physicochemical properties of drug molecules by increasing their water solubility, and has a high affinity for complexing with targets due to its dipole moment.Electric Literature of C5H3ClN4O
Referemce:
Pyridazine – Wikipedia,
Pyridazine | C4H4N2 – PubChem