New Coumarins from Citrus Plants

Four new coumarins, named peroxytamarin (1), cis-casegravol (5), citrusarin-A (7), and citrusarin-B (8), were isolated from root of Citrus plants and their structures were elucidated by chemical and spectrometric methods. Citrusarin-B (8), a coumarin having both a dimethylpyran ring and a dihydrofuran ring in the molecule, was also synthesized.