[Development of Functional Compounds Using Chemically Unstable Compounds Obtained from Medicinal Plants].

Sulfur- or nitrogen-containing compounds from medicinal plants exhibit various biological activities such as anticancer potential. Developing efficient strategies to isolate or synthesize these compounds or their derivatives is a remarkable achievement. We have isolated several sulfur-containing compounds such as tetrahydro-2H-difuro[3,2-b:2',3'-c]furan-5(5aH)-one derivatives from Allium plants. We have devised a unique approach for the rapid preparation of thiopyranones using the regioselective sequential double Diels-Alder reaction; we used a naturally-occurring chemically-unstable intermediate such as thioacrolein, which is produced from allicin, a major component in garlic. The cytotoxicity of the synthetic thiopyranones against cancer stem cells (CSCs) was equal to or higher than that of (Z)-ajoene, the reference compound.