An unsaturated derivative at the 4-position of 6-tert-butyl-1,1-dimethylindane corresponding to the following formula: ##STR1## in which: X represents: a divalent radical of formula: ##STR2## and Y represents a divalent radical of following formula: ##STR3## R.sub.1 represents --CH.sub.3, --(CH.sub.2).sub.p --OR.sub.4, --(CH.sub.2).sub.p --COR.sub.5 or --S(O).sub.t --R.sub.6, p being 0, 1, 2 or 3, t being 0, 1 or 2, R.sub.4 represents H, lower alkyl, --COR.sub.7, aryl, aralkyl, mono- or polyhydroxyalkyl, or a polyether radical, R.sub.5 represents H, lower alkyl, --OR.sub.8 or ##STR4## R.sub.6 represents H or lower alkyl, R.sub.7 represents lower alkyl, R.sub.8 represents H, alkyl, alkenyl, alkynyl, aryl, aralkyl, mono- or polyhydroxyalkyl, a sugar residue selected from the group consisting of residues deriving from glucose, galactose, mannose and glucuronic acid or an amino acid residue deriving from lysine, glycine and aspartic acid, r' and r", which are identical or different, represent H, lower alkyl, --COR.sub.7, aryl, a sugar residue selected from the group consisting of residues deriving from glucose, galactose, mannose and glucuronic acid or an amino acid residue deriving from lysine, glycine and aspartic acid, or r' and r", taken together form a heterocycle selected from the group consisting of piperidino, morpholino, pyrrolidino and piperazino radical, the latter optionally being substituted in the 4-position by a C.sub.1 -C.sub.6 alkyl radical or a mono- or polyhydroxyalkyl, and the salts of the compounds of formula (I), when R.sub.1 represents a carboxylic acid functional group, and the geometrical and optical isomers of the compounds of formula (I).