3,3,7,11-Tetramethyltricyclo[6.3.0.0^<2,4>]undecane skeleton is found in a number of natural products, which are divided into two groups, aromadendranes (I) and alloaromadendranes (II). Recently, some coupled compounds with other organic moieties were found, e.g., macrocarpals (3), which were exhibiting HIV-RTase inhibitory activities. We planned to develop a general synthetic route to these compounds. We selected 7-substituted tricyclo[6.3.0.0^2,4>]undecenone derivatives (4) as common key intermediates for both groups, I and II. Both nuclei would be obtained by control in the stereochemistry of the reduction of C-8-C-9 double bond. (+)-3-Carene (5) was converted to a cyclic β-keto ester 8 in a 5-step sequence. 4-Methyl derivatives (10 and 11) and 4-CH_2OTBDMS derivatives (12 and 13) were synthesized from 8. Compound 10 was converted to a tricyclic enone (4a) by allylation at C-2, the Wacker oxidation followed by the aldol ring closing reaction. Similarly, the enone 4b was obtained from 12. Stereoselective introduction of a methyl group at C-11 of 4 was accomplished to afford 18 and 22 selectively. Deoxygenation of 18 gave (+)-1,2-didehydroaromadendrane (24). Catalytic hydrogenation of 22 afforded a B/C-trans compound 25 preferentially. The Birch reduction of 22 also produced only 25. Compound 25 was converted to (+)-aromadendrene (1) by reduction of the ketone, esterification with PTC-Cl, radical reductive deoxygenation, deprotection of TBDMS, mesylation followed by elimination with DBU. (-)-Alloaromadendrene (2) was obtained from 22 by an intramolecular-type hydrogen migration occurring in the reduction of the tosylhydrazone with a hydride as a crucial step.