Suggested Reaction 1.3.4.-

Left

5,6-Dihydroxy-3-methyl-2-oxo-1,2-dihydroquinoline
+1,4-Dithiothreitol

Right

5,6-Dihydroxy-3-methyl-2-oxo-1,2,5,6-tetrahydroquinoline
+Oxidized dithiothreitol

[BiSSCat | GREP ]