A new process prepares retiferol derivatives of formula I:
1
wherein
A is —C≡C— or —CH═CH—, and
R
1
and R
2
are independently of each other lower alkyl or lower perfluoroalkyl,
one version couples ketones of formula II with compounds of formula III
A second version couples phosphinoxides of formula IV with aldehydes of formula V. Compounds of formula I are useful in the treatment or prevention of hyperproliferative skin diseases and for reversing the conditions associated with photodamage.