The invention relates to novel compounds of formula (I) wherein R.sub.1 represents a polymer, aryl or alkyl group, R.sub.2 represents a hydrogen atom, a halogen atom, a radical CN, CF.sub.3, OH, OCF.sub.3, COOH, R.sup.7, OR.sup.7 or OCOR.sup.7, R.sup.3 represents an represents an alkyl radical. The invention also relates to a cosmetic composition comprising said compounds and to the use thereof to reduce and/or curb hair loss i.e. to increase and/or stimulate the growth of said hair ##STR00001##