Selected w-nitroacetophenones, formed by the alcoholic cleavage of 2-nitroindandiones, have been shown to inhibit the homocytotropic antibody-antigen induced passive cutaneous anaphylaxis reaction in the rat. The enzymatic cy-clization of these derivatives to the parent nitroindandione has been demonstrated both in vivo and in vitro and this process is suggested as a possible prerequisite to biological activity.
