New NO‐Donors with Antithrombotic and Vasodilating Activities, IV: Chemical Reactivity of Nitrosimines and its Implications for their Pharmacologic Properties

Nitrososydnone‐5‐imines and Thiazole‐2‐nitrosimines are susceptible to photolytic cleavage of the NNO bond. This can be achieved with a tungsten lamp. In water the corresponding syndnone imine salts are formed in 90% yield at 37°C. Only at higher temp. (70°C) ring opening is observed. In methanol about 25% of sydnones are obtained. On the other hand NO⋅ and N 2 O were detected in the head space of the reaction vials when oxygen was excluded. The formation of N 2 O from nitrososydnone imine was increased up to elevenfold by glutathione while the amount of NO⋅ was decreased. In the presence of light and thiols soluble guanylate cyclase (s‐GC) was stimulated. The results suggest that the nitroxylate anion NO − plays an important role in the stimulation of s‐GC.