As a result, we observed no increase in the rate of 2',3'-cGMP, as a reaction intermediate catalyzed by cyclizing
RNases (Figure 3(b)).
On the other hand, 2-thioxo-pyrido[2,3-d]pyrimidine-6-carbonitrile 10 was obtained by cyclizing
8 with carbon disulfide in the presence of sodium hydroxide at room temperature  followed by acidification with diluted hydrochloric acid.
The hydration decouples the nitrile-nitrile associations that cause cyclizing
and thermal degradation well below the melting temperature of pure PAN (320[degrees]C).