Structure-activity relationship of norzoanthamine exhibiting significant inhibition of osteoporosis

Norzoanthamine is a zoanthamine-type alkaloid from the colonial zoanthid Zoanthus sp. Norzoanthamine hydrochloride, which suppresses the decrease in bone weight and strength in ovariectomized mice, could be a good candidate for an osteoporotic drug. Although the relative configuration of norzoanthamine was established based on an X-ray crystallographic analysis, the absolute stereochemistry of norzoanthamine remains unclear. To investigate their biogenesis and mechanisms of biological action, we conducted chemical and spectroscopic studies to determine the absolute configuration of norzoanthamines.