Are there alternatives to imidazo[5,1-d]-1,2,3,5-tetrazine-8-carboxylic acid, 3,4-dihydro-3-methyl-4-oxo-(CAS: 113942-30-6) in synthesis?

While imidazo[5,1-d]-1,2,3,5-tetrazine-8-carboxylic acid, 3,4-dihydro-3-methyl-4-oxo- is a specific compound, researchers have explored alternative tetrazine derivatives such as 1,2,3,4-tetrazine and 1,2,3,5-tetrazine. Other synthetic routes using picolinic acids or related compounds can also be considered as substitutes. These alternatives offer similar functional groups but may differ in reactivity and stability.