χ-caroten-4-one, assigned to tedanin, the main carotenoid pigment of the marine sponge “Tedania digitata (O. Schmidt),” has been confirmed by total synthesis starting with β,χ-carotene. An isomer, 3-hydroxy-2,3-didehydro-β,φ-caroten-4-one, was also synthesized from β,φ-carotene.