Kazumasa Matsuo

Cu(II)-catalyzed acylation by thiol esters under neutral conditions: tandem acylation-wittig reaction leading to a one-pot synthesis of butenolides.

The first catalytic acylation of alcohols with a thiol ester present in Wittig reagents under neutral conditions catalyzed by the Cu(II) salt through a push-pull mechanism is reported. Furthermore, a new methodology for the one-pot lactonization of acyloins by a copper catalyst is developed. The synthetic utility of this method for the synthesis of natural products is shown.

Total synthesis of (+)- and (-)-sundiversifolide via intramolecular acylation and determination of the absolute configuration.

Intramolecular acylation of an organolithium leads to an efficient stereocontrolled total synthesis of both enantiomers of sundiversifolide. The absolute configuration was determined by HPLC analysis and allelopathy assay. The gamma-lactone moiety resulted from a butenolide was obtained by the condensation of a bicyclic alpha-hydroxyhemiacetal with Ph3P=CMe(CO2R).

(-)-Xanthatin selectively induces GADD45γ and stimulates caspase-independent cell death in human breast cancer MDA-MB-231 cells

exo-Methylene lactone group-containing compounds, such as (--)-xanthatin, are present in a large variety of biologically active natural products, including extracts of Xanthium strumarium (Cocklebur). These substances are reported to possess diverse functional activities, exhibiting anti-inflammatory, antimalarial, and anticancer potential. In this study, we synthesized six structurally related xanthanolides containing exo-methylene lactone moieties, including (--)-xanthatin and (+)-8-epi-xanthatin, and examined the effects of these chemically defined substances on the highly aggressive and farnesyltransferase inhibitor (FTI)-resistant MDA-MB-231 cancer cell line. The results obtained demonstrate that (--)-xanthatin was a highly effective inhibitor of MDA-MB-231 cell growth, inducing caspase-independent cell death, and that these effects were independent of FTase inhibition. Further, our results show that among the GADD45 isoforms, GADD45γ was selectively induced by (--)-xanthatin and that GADD45γ-primed JNK and p38 signaling pathways are, at least in part, involved in mediating the growth inhibition and potential anticancer activities of this agent. Given that GADD45γ is becoming increasingly recognized for its tumor suppressor function, the results presented here suggest the novel possibility that (--)-xanthatin may have therapeutic value as a selective inducer of GADD45γ in human cancer cells, in particular in FTI-resistant aggressive breast cancers.

(−)-Xanthatin up-regulation of the GADD45γ tumor suppressor gene in MDA-MB-231 breast cancer cells: Role of topoisomerase IIα inhibition and reactive oxygen species

Previously, we reported that (-)-xanthatin, a naturally occurring xanthanolide present in the Cocklebur plant, exhibits potent anti-proliferative effects on human breast cancer cells, accompanied by an induction of the growth arrest and DNA damage-inducible gene 45γ (GADD45γ), recognized recently as a novel tumor suppressor gene. However, the mechanisms mediating this activation were unknown. Topoisomerase IIα (Topo IIα) inhibition has been reported to produce a cell death response accompanied by an atypical DNA laddering fragmentation profile, similar to that noted previously for (-)-xanthatin. Therefore we hypothesized that (-)-xanthatins GADD45γ activation was mediated through the Topo IIα pathway. Here, we identify that (-)-xanthatin does function as a catalytic inhibitor of Topo IIα, promoting DNA damage. In addition, reactive oxygen species (ROS) were elevated in cells treated with this agent. Mechanistically, it was determined that the induced levels of GADD45γ mRNA resulting from (-)-xanthatin exposures were stabilized by coordinately produced ROS, and that the consequent induction of GADD45γ mRNA, GADD45γ protein and ROS generation were abrogated by co-treatment with N-acetyl-l-cysteine. Taken together, the data support the concept that Topo IIα inhibition by (-)-xanthatin is a trigger that stimulates expression of DNA damage-inducible GADD45γ mRNA and that concomitantly produced ROS act downstream to further enhance the GADD45γ mRNA/GADD45γ protein induction process, resulting in breast cancer cell death.

Efficient synthesis of dissymmetric malonic acid S, O -esters via monoalcoholysis of symmetric dithiomalonates under neutral conditions

A novel method for the highly selective synthesis of dissymmetric S,O-malonates starting from symmetric diphenyl dithiomalonates under neutral conditions is described. The key step is the thermal formation of an acylketene, the stability of which would contribute to the selectivity. The synthetic utility of the dissymmetric S,O-malonates is also shown.