(2R,3R)-3-Ethyl-2,3-dimethyl-3,4,5,6-tetrahydro-2H-pentalen-1-one

3,3-dimethyl-2,3,5,6-tetrahydro-1H,4H-pentalen-1-one

2,3,3-trimethyl-2,3,5,6-tetrahydropentalen-1(4H)-one

(3bR,7aR)-3b-Methyl-2,3,3b,4,5,6,7,7a-octahydro-1H-cyclopenta[a]inden-8-one

1-methylcyclopentyl acetate