Oxalyl chloride represents a versatile C₂ building block for cyclization reactions. A variety of cyclization reactions of oxalyl chloride are known which involve the formation of two carbon-heteroatom bonds. In contrast, one-pot cyclizations of oxalyl derivatives which proceed by formation of at least one carbon-carbon bond are more rare. In recent years, a number of such cyclizations have been developed which rely on the reaction of oxalyl chloride with silyl enol ethers. These reactions allow for an efficient synthesis of various oxygen heterocycles, such as γ-alkylidenebutenolides, maleic anhydrides and isotetronic acids. The cyclization reactions, which involve the formation of a carbon-carbon and a carbon-oxygen bond, generally proceed with excellent regioselectivity.

Jatropha curcas (JCP1), Pyrenacantha staudtii (PS), Picralima nitida (ZI) and Jatropha gossypifolia (JCP2) are plants used in the African folklore for the treatment of various cancers. This study investigated the in vitro anticancer effects of the ethanol extracts against human epithelial MCF-7 breast cancer cells in a dose-dependent manner (1–50 μg/ml) by using cell cycle analysis, viability assay, annexin V/PI staining, TUNEL method and expression determination of apoptotic and adhesion relevant proteins. Adhesion processes were monitored by detachment via flow cytometry, β1-integrin expression and formation of the actin cytoskeleton. The three extracts, termed PS, JCP1 and JCP2 at a concentration of 10 μg/ml induced cell death in MCF-7 breast cancer cells verified by high amounts of PI-positive cells in the cell cycle analysis, Annexin V/PI staining and DNA fragmentation measurements. In parallel cell detachment was accompanied by decreased β1- integrin expression and phosphorylation of the focal adhesion kinase at Tyr397. ZI extract was the exception by the increasing β1-integrin expression and strengthening the cortical actin cytoskeleton. However, all four plant extracts mediated strong anti-cancer properties with IC50 values between 23–38 μg/ml. PS, JCP1 and JCP2 were found to be very active against MCF-7 cells by inducing anoikis and therefore possessing vast potential as medicinal drugs especially in estrogen receptor positive breast cancer treatment. ZI mediated their anti-cancer action by different signaling mechanisms which should be analyzed in future studies. Our results further supported the idea that medicinal plants can be promising sources of putative anticancer agents.