Dibenzofuran compounds and pharmaceutical/cosmetic compositions comprised thereof

A dibenzofuran compound having the structural formula (I):

• ##STR11## in which R is a hydrogen atom, a halogen atom, a lower alkyl radical having 1 to 6 carbon atoms, a lower acyl radical having 1 to 10 carbon atoms or an OR' radical;
• A is a radical selected from the group consisting of the following formulae (IIa-IIc):
• ##STR12## wherein R.sub.1 is (i) a hydrogen atom,
• (ii) the --CH.sub.3 radical,
• (iii) an --CH.sub.2 --O--R.sub.5 radical,
• (iv) an --OR.sub.5 radical
• (v) a ##STR13## radical, or (vi) an --S(O).sub.t R.sub.6 radical;
• R.sub.2 is a hydrogen atom or an --OR.sub.5 radical;
• R.sub.3 and R.sub.4 are independently a hydrogen atom, a lower alkyl radical having 1 to 6 carbon atoms or a --(X).sub.n --(CH.sub.2).sub.m --R.sub.7 radical, or R.sub.3 and R.sub.4 may together form an oxo (.dbd.O) group, a thioxo (.dbd.S) group, an oxime group or a group derived from the oxime (R.sub.6 --O--N.dbd.), an epoxy group, or a dioxolane group (--O--(CH.sub.2).sub.q --O--) wherein q is equal to 2 or 3;
• R.sub.3 ' and R.sub.4 ' are independently a hydrogen atom, a lower alkyl radical having 1 to 6 carbon atoms or a lower acyl radical having 1 to 6 carbon atoms;
• t is equal to 0, 1 or 2;
• R.sub.5 is a hydrogen atom, a lower alkyl radical having 1 to 6 carbon atoms, or a lower acyl radical having 1 to 6 carbon atoms;
• R.sub.6 is a hydrogen atom, an --N(R',R'") radical, or an --OR.sub.8 radical;
• R.sub.6 is a hydrogen atom or a --(CO).sub.p --R.sub.9 radical, wherein p is 0 or 1;
• R.sub.8 and R' are independently a hydrogen atom, an alkyl radical having from 1 to 20 carbon atoms, a mono- or polyhydroxyalkyl radical respectively having 1 to 6 or 2 to 6 carbon atoms, an optionally substituted phenyl radical or optionally substituted benzyl or phenethyl radical wherein the substituents on said phenyl, benzyl or phenethyl radical, if present, are selected from the group consisting of halogen, hydroxyl, nitro and methoxy groups;
• R.sub.9 is a hydrogen atom, an alkyl radical, having 1 to 20 carbon atoms, an alkenyl radical which is a linear or branched radical having 1 to 20 carbon atoms and having at least one ethylenic double bond, an alkynyl radical, which is a linear or branched radical having 1 to 20 carbon atoms and having at least one acetylenic double bond, a phenyl radical, an --OR.sub.7 radical wherein m is other than 0, or an --N(R',R'") radical;
• R' and R'", which may be identical or different, are each a hydrogen atom, a lower alkyl radical having 1 to 6 carbon atoms, a mono- or polyhydroxyalkyl radical respectively having 1 to 6 or 2 to 6 carbon atoms, an optionally substituted phenyl radical, an optionally substituted benzyl or phenethyl radical wherein the substituents on said phenyl, benzyl or phenethyl radical, if present, are selected from the group consisting of halogen, nitro, hydroxyl and methoxy group;
• X is an oxygen or sulfur atom;
• and n ranges from 0 to 1 and m from 0 to 10;
• or a pharmaceutically/cosmetically acceptable salt or optical or geometric isomer thereof.