New chromane and chromene meroterpenoids from flowers of Rhododendron rubiginosum Franch. var. rubiginosum

Six new chromane and chromene meroterpenoids, rubiginosins A-F (1-2, and 4-7), were isolated from the flowers of Rhododendron rubiginosum Franch. var. Rubiginosum. Their absolute configuration of the chiral center at C-2 was established as S by chromane/chromene helicity rule and X-ray single crystal diffraction.129