Compound 21

(1R*,5S*,7R*)-3-Benzoyl-4-methoxy-1,8,8-trimethyl-5,7-bis(3-methylbut-2-en-1-yl)bicyclo[3.3.1]non-3-ene-2,9-dione

From: The total synthesis of hyperpapuanone, hyperibone L, epi-clusianone and oblongifolin A