Solvent-directed intramolecular hydrofunctionalization of readily available o -alkynoylphenols 1 was successfully achieved under reagent-free conditions.

With the several targets of cancer treatment, inhibition of DNA topoisomerase activity is one of the well-known focuses in cancer chemotherapy. Here, we describe the design and synthesis of a novel series of pyrazolo[4,3-f]quinolines with potential anticancer/topoisomerase inhibition activity. Forty newly designed pyrazolo[4,3-f]quinoline derivatives were synthesized via inverse imino Diels–Alder reaction. The antiproliferative activity of the synthesized derivatives was initially measured in the human NUGC-3 cancer cell line. Then, the selected compounds 1B, 1C, 1M, 2A, 2D, 2E, 2F, and 2R with higher activity among tested compounds were screened against six cancer cell lines, including ACHN, HCT-15, MM231, NCI-H23, NUGC-3, and PC-3. The results demonstrated that the compounds 1M, 2E, and 2P were most effective in all cancer cell lines exhibiting GI₅₀ below 8 µM. Among them, 2E showed an equivalent inhibition pattern of topoisomerase IIα activity to that of etoposide, positive control at a 100 µM dose.

In continuation of studies for α-MSH stimulated melanogenesis inhibitors, we have evaluated the design, synthesis, and activity of a new series of chlorogenic acid (CGA) analogues comprising pyridine, pyrimidine, and diacyl derivatives. Among nineteen synthesized compounds, most of them (fifteen) exhibited better inhibitions of melanin formation in B16 melanoma cells. The results illustrated that a pyridine analogue 6f and a diacyl derivative 13a of CGA showed superior inhibition profiles (IC₅₀: 2.5 ± 0.7 μM and 1.1 ± 0.1 μM, respectively) of α-MSH activities than positive controls, kojic acid and arbutin (IC₅₀: 54 ± 1.5 μM and 380 ± 9.5 μM, respectively). The SAR studies showed that both –CF₃ and –Cl groups exhibited better inhibition at the meta position on benzylamine than their ortho and para positions. In addition, the stability of diacyl analogues of CGA in methanol monitored by HPLC for 28 days indicated the steric bulkiness of acyl substituents as a key factor in their stability.