A series of furoxan derivatives of chromone were prepared. The antiproliferative activities were tested against five cancer cell lines HepG2, MCF-7, HCT-116, B16, and K562, and two normal human cell lines L-02 and PBMCs. Among them, compound 15a exhibited the most potent antiproliferative activity. It was also found 15a produced more than 8 mM of NO at the peak time of 45 min by Griess assay. Generally, antiproliferative activity is positively related to NO release to some extent. Further in-depth studies on apoptosis-related mechanisms showed that 15a caused S-phase cell cycle arrest in a concentrationdependent manner and induced apoptosis significantly through mitochondria-related pathways. Human apoptosis protein array assay also demonstrated 15a increased the expression levels of pro-apoptotic Bax, Bad, HtrA2 and Trail R2/DR5. The expression of catalase and cell cycle blocker claspin were similarly upregulated. In balance, 15a induced K562 cells death through both endogenous and exogenous pathways.

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Diterpenoids are widely distributed natural products and have caused considerable interest because of their unique skeletons and antibacterial and antitumor activities and so on. In light of recent discoveries, ent-kaurane diterpenoids, which exhibit a wide variety of biological activities, such as anticancer and anti-inflammatory activities, pose enormous potential to serve as a promising candidate for drug development. Among them, spirolactone-type 6,7-seco-ent-kaurane diterpenoids, with interesting molecular skeleton, complex oxidation patterns, and bond formation, exhibit attractive activities. Furthermore, spirolactone-type diterpenoids have many modifiable sites, which allows for linking to various substituents, suitable for further medicinal study. Hence, some structurally modified derivatives with improved cytotoxicity activities are also achieved. In this review, natural bioactive spirolactone-type diterpenoids and their synthetic derivatives were summarized.

Poly-substituted quinolines are scaffolds with diverse applications as pharmaceuticals, agrochemicals, electroluminescent materials, and dyestuffs. Herein, we present an effective scheme for the green synthesis of two multiply substituted quinoline derivatives from a singular substrate via regulating free-radical duality. Photo-catalytically generated imine radicals can undergo intramolecular Michael addition (nucleophilic 1,4-addition) to produce 3,4-disubstituted quinolines via a novel rearrangement in the presence of an inorganic base. Alternatively, they can react via an intramolecular anti-Michael addition (electrophilic 1,3-addition) in the presence of an organic base to furnish 2,3-disubstituted quinolines. The high-atom economy, good yields, mild reaction condition, simple experimental setup of this methodology, will prompt the development of Poly-substituted quinolines and other heterocycles synthesis via using intramolecular Michael addition and anti-Michael addition of free radicals. Moreover, our results suggests the theory that the electrophilic / nucleophilic bias of free radicals is determined by their structure is incomplete, the electrophilic/nucleophilic bias can be regulated by altering the reaction conditions, which can improve the efficiency of divergent synthesis.