Modification of 2-acetamido-3-chloro-1, 4-naphthoquinone, which has potent antiplatelet, antiallergic and antiinflammatory activities, led to a series of 2, 3-disubstituted 1, 4- naphthoquinones. Some of these compounds showed significant antiplatelet, antiallergic and antiinflammatory activities. Among them, 2-methoxy-3-chloro-1, 4-naphthoquinone (15) and 2-ethoxy-3-chloro-1, 4-naphthouinone (17) exhibited potent inhibitory effects on ...