A novel homocyclotirucallane. sinetirucallol (1), and two additional new di
hydrophenanthrenes, sinensols G (2) and H (3), were isolated from the aeria
l parts of Spiranthes sinensis (PERS.) AMES. Their structures were determin
ed by various spectral analyses, including MS and two-dimentional nuclear m
agnetic resonance techniques. The structure of compound I was further confi
rmed by single-crystal X-ray analysis. The absolute configuration of I was
determined by modified Mosher's method.