As a new precursor for a hydrogen-bonded open-shell system, we have designed and synthesized 2,5,8-tri-tert-butyl-4,9-dihydroxyphenalenone 1 from commercially available 2,7-dimethoxynaphthalene in nine steps. The neutral radical generated from I with active PbO2 exhibits higher stability compared with other 6-oxophenalenoxyl derivatives in the solid state. From the results of ESR and ENDOR/TRIPLE spectroscopies and MO calculations, the structure of the radical is identified to be monoradical 2 with a hydroxyl group.