New cannabinoid-like chromane and chromene derivatives from Rhododendron anthopogonoides.

Two new cannabinoid-like chromane and chromene derivatives named anthopogocyclolic acid (1) and anthopogochromenic acid (2) and five related compounds (3-7) which are known as synthetic analogues of cannabinoids: cannabichromene (CBC) type, cannabicyclol (CBL) type, and cannabicitran (CBT) type, have been isolated together with geranyl orsellinic acid (8) from the Chinese medicinal plant Rhododendron anthopogonoides. Their structures were elucidated based on spectroscopic and chemical evidence. The absolute configuration of the asymmetric carbons at C-2 of 1-7 was determined to be S from their circular dichroism (CD) spectra. Compounds 2, 4 and 6 inhibited compound 48/80-induced histamine release from rat peritoneal mast cells.