Pyridine → 5-Iminopentanoate<br><br>Comments:<br>This rule handles the unsubstituted pyridine ring cleavage pathway. An initial reduction step breaks aromaticity of the ring, forming a 1,4-dihydropyridine intermediate which is predicted to undergo hydrolytic cleavage to produce 5-iminopentaldehyde (<a href="http://www.ncbi.nlm.nih.gov/sites/entrez?Db=pubmed&Cmd=ShowDetailView&TermToSearch=1147895">Watson and Cain, 1975</a>). The aldehyde is quickly oxidized to form 5-iminopentanoate (bt0003). The iminoaldehyde is postulated to transition between the linear form and a cyclic tautomer (see graphic). This rule does not handle the tautomerization.
