Study on the development of biological-active compounds after the model of natural products

In reviewing my lifework, I wish to summarize the results of studies on the development of new biological-active compounds. The following subjects are discussed: 1) syntheses and biological activities of benzoxazole derivatives, 2) structure-activity relationships of phyllodulcin, a natural sweetner, and 3,4-dihydroisocoumarins for sweetness, 3) syntheses and structure-activity relationships of spiro[isocoumarin-piperidine] analogs for antiallergic activity, 4) design, structure-activity relationships, and a mechanism of antitumor action of bistropolone derivatives, 5) design, structure-activity relationships of fused tetracyclic quinolines for antitumor activity.