Artificial Host Molecules to Covalently Capture 8-Nitro-cGMP in Neutral Aqueous Solutions and in Cells.

New 1,3-diazaphenoxazine derivatives (nitroG-Grasp-Guanidine, NGG) have been developed to covalently capture 8-nitro-cGMP in neutral aqueous solutions, which furnish a thiol reactive group to displace the 8-nitro group and a guanidine unit for interaction with the cyclic phosphate. The thiol group was introduced to the 1,3-diazaphenoxazine skeleton through a 2-aminobenzylthiol group (NGG-H) and its 4-methyl (NGG-Me) and 6-methyl (NGG-Me) substituted derivatives. The covalent adducts were formed between the NGG derivatives and 8-nitro-cGMP in neutral aqueous solutions.