Synthesis and nematocide activity of S-glycopyranosyl-6,7-diarylthiolumazines Original Research Article

6,7-Diaryl derivatives of mono and di-S-glycopyranosylthiolumazine derivatives 5–8 were prepared to test their nematocide activity. In vitro tests against Caenorhabditis elegans were performed and it was found that monosubstituted derivatives 5–7 showed higher activity than the corresponding unsubstituted 2-thiolumazines 1–3, whilst 2-S,4-S-di-glycopyranosylpteridine derivative 8 was inactive in contrast to unsubstituted derivative 4. In order to check whether the lack of activity of 8 was due to the two bulky substituents of the pteridine nucleus, 2-S,4-S-dimethyl derivative 9 was synthesized and assayed showing also lack of activity. A theoretical study on the stability of the different possible tautomers of compound 4 was carried out in an attempt to explain some, in appearance, anomalous 13C NMR data of this compound.