Compound 20

(1R,3R,3aS,4R,6aS,7R,9R)-1,4,7-Trimethyl-9-(2-methylprop-1-en-1-yl)-3-nitro-2,3,3a,4,5,6,6a,7,8,9-decahydro-1H-phenalene

From: Pseudopterosin synthesis from a chiral cross-conjugated hydrocarbon through a series of cycloadditions