First determination of the absolute stereochemistry of a naturally occurring 1,1'-biphenanthrene, (--)-blestriarene C, and its unexpected photoracemization.

A naturally occurring 1,1'-biphenanthrene, blestriarene C, was prepared and its absolute stereochemistry was determined to be Sa-(-) by an empirical method, during which the compound was found to undergo rapid photoracemization even under ambient light exposure.