3-ACETONYLBICYCLO[6,3.0]UNDECANE-2,6-DIONE,(I), ,4-DIMETHYLBICYCLO[6.3.0]-UNDECANE-2,6-DIONE,(II), HYLTETRACYCLO[8.2.1.0(1,5).0(7,11)]TRIDECAN-13-ONE MONOHYDRATE,(III), AND ICYCLO[9.3.0.0(2,6)]TETRADEC-5-ENE-4,10-DIONE,(IV)

The crystal structures of the four title compounds, C14H20O3, (I), C16 H24O3, (II), C14H20O3 H2O, (III), and C16H22O2, (IV), which were obtai ned during studies of the preparation of C-5-C-8-C-5 fused-ring compou nds, have been determined by X-ray diffraction.