The invention relates to the use of compounds of the formula I ##STR1## in which X is the divalent radical of oxygen, a carbonyl radical, optionally aliphatically substituted imino or the radical .dbd.CR.sup.9 R.sup.10, Y is a carbonyl group or the radical .dbd.CR.sup.9 R.sup.10, R.sup.1 and R.sup.2 are identical or different electron-withdrawing radicals, chosen from the group consisting of cyano, alkyl- or arylcarbonyl, alkyloxy- or aryloxycarbonyl, optionally substituted aminocarbonyl, alkyl- or arylsulfinyl, alkyl- or arylsulfonyl and optionally substituted aminosulfonyl, R.sup.3 is a hydrogen atom, a cyano, hydroxyl, carboxyl or aminocarbonyl group or a C.sub.5 -C.sub.20 -aryl radical or C.sub.1 -C.sub.20 -alkylradical optionally bonded via an oxygen bridge, an aminocarbonyl bridge or oxycarbonyl bridge, R.sup.4 is a hydrogen atom, a hydroxyl group, an amino group, or a C.sub.5 -C.sub.20 -aryl radical or C.sub.1 -C.sub.20 -alkyl radical optionally bonded via an oxygen bridge, and R.sup.5 to R.sup.10 independently of one another are hydrogen or C.sub.1 -C.sub.20 -alkyl radicals and where in addition R.sup.7 and R.sup.8 together with the chain carbon atom are a carbonyl group, as photostable UV filters in cosmetic and pharmaceutical preparations for protecting human skin and human hair from solar rays, alone or together with compounds which absorb in the UV region and are known per se for cosmetic and pharmaceutical preparations.