Regioselective synthesis and evaluation of 2-amino 3-cyano chromene-chrysin hybrids as potential anticancer agents.

The first example of Ca(OH)2-activated p-regioselective synthesis of chrysin-fused chromene was reported through a cascade Michael/cyclization of chrysin and arylidenemalononitrile. The newly synthesized structurally diverse 2-amino 3-cyano chromene-chrysin hybrids 3 were evaluated for their in vitro anticancer activity, and some of the compounds showed stronger anti-proliferative activity against K562, PC-3, A549 and NCI-H1299 than parent compound chrysin, and demonstrated equipotent potency compared with the reference drug of cisplatin. In particular, compound 3h had the highest cytotoxicity towards K562 cells (IC50 = 6.41 µM). Furthermore, compound 3h induced apoptosis of K562 cells in a concentration-dependent manner, as well as induced the apoptosis possibly through promoting the formation of apoptotic DNA of cancer cell via the intrinsic apoptotic pathway. Thus, our results provide in vitro evidence that compound 3h may be a potential candidate for the development of new anti-tumour drugs.

An asymmetric iminium ion catalysis-enabled cascade cycloaddition reaction of chromone-oxindole synthons with enals: construction of a spirooxindole-hexahydroxanthone framework.

We report the first asymmetric iminium ion catalysis-enabled cascade cycloaddition reaction of bifunctional chromone-oxindole synthons and α,ß-unsaturated aldehydes. This allowed one quaternary and four tertiary contiguous stereogenic centers to be constructed in a single operation. A range of spirooxindole-hexahydroxanthone molecules are obtained with up to 62% yield, >20 : 1 dr and >99% ee. This reaction has not only provided a new approach for constructing hexahydroxanthone-fused scaffolds by utilizing asymmetric iminium ion catalysis, but also advanced the chemistry of diversity-oriented synthesis based on bifunctional chromone synthons.

Organocatalytic Reaction of Chromone-Oxindole Synthon: Access to Chromanone-Based Spirocyclohexaneoxindoles with Five Adjacent Stereocenters.

An efficient strategy for stereo-controlled synthesis of potential biological and structurally complex chromanone-based spirocyclohexaneoxindoles via an organocatalytic domino formal double Michael cycloaddition of bifunctional chromone-oxindole synthons and nitroolefins is reported. These products possessing five adjacent stereocenters including one spiro quaternary carbon center, were smoothly afforded in up to 85% yield, >99% ee, and >20:1 dr. This strategy benefits from the intramolecular nature of the second Michael reaction step, through counterbalancing the lower electrophilicity of these unactivated chromones to facilitate the reaction.