Abstract: Carbon-13 NMR spectra of a number of natural (-) ent-kauranoids have been studied. The rule of change in chemical shifts produced by the change of substituents has been summarized ( be published somewhere ). By above-mentioned rule, chemical structure of bulleyanin has been altered as lα, 3β, 7β, 11β-te-tra-acetoxy-12α-hydroxy-ent-kaur-16-en-15-one ( 1 ).

Key words: Bulleyanin