Tetracyclic chromane derivatives from Rhododendron anthopogonoides.

Four new chromane derivatives, anthopogochromane (1), anthopogochromene A (2), anthopogochromene B (3), and anthopogochromene C (4), and two known compounds, daurichromenic acid (5) and ilicicolinic acid B (6), have been isolated from the Chinese medicinal plant Rhododendron anthopogonoides. The S absolute configuration of the stereogenic carbons in the chromane and chromene rings of 1-4 was determined from their circular dichroism spectra. Compounds 1 and 2 inhibited compound 48/80-induced histamine release from rat peritoneal mast cells.