Thio-flavanone, Thio-chromanone und -chromonole. (Gemeinsam mit den HHrn. W. Flemming, E. Scholz und V. Löwensohn.)

Recent advances in cyclization reactions of isatins or thioisatins via C–N or C–S bond cleavage

This review summarizes recent developments on cyclization reactions induced by the C–N or C–S bond cleavage of isatins or thioisatins in the last 5 years, which produce fused products instead of spiro compounds.

Synthesis and structure–activity relationships of thioflavone derivatives as specific inhibitors of the ERK-MAP kinase signaling pathway

Condensation of nitrobenzaldehydes 3 and alpha-[o-(p-methoxybenzylthio)benzoyl] sulfoxide 4 gave alpha-sulfinyl enones 5. Treatment of 5 with formic acid caused cyclization followed by debenzylation to afford 3-(methylsulfinyl)thioflavanones 6. Double-bond formation with elimination of methanesulfenic acid was performed by refluxing 6 in benzene, and, finally, the nitro group of 2-phenyl-4H-1-benzothiopyran-4-one (thioflavones) 7 was reduced with tin in tetrafluoroboric acid. Various 2'-aminothioflavones 8 thus prepared were evaluated for their inhibitory effects on the ERK-MAP kinase pathway. In a cell-based assay, 2-(2'-amino-3'-methoxyphenyl)-4H-1-benzothiopyran-4-one (8b) showed a more potent inhibitory effect than the corresponding oxygen compound (PD98059, 1) on the Raf-induced activation of the ERK-MAP kinase pathway as well as cell proliferation. Furthermore, compound 8b selectively and potently inhibited the proliferation of tumor cells in which the ERK-MAP kinase pathway is constitutively activated.