Abstract: The invention relates to compounds of the formula ##STR1## wherein R.sub.1 is hydrogen or methyl; ##STR2## wherein R.sub.2 is lower alkyl; R.sub.3 is phenyl, or phenyl substituted by 1 to 3 substituents selected from the group consisting of halo, lower alkyl, and lower alkoxy; and R.sub.4 is hydrogen or methyl or the corresponding hydroxy acid of formula ##STR3## and R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are as described above; or a pharmaceutically acceptable salt of said acid, a C.sub.1-4 alkyl ester of said acid, an acetylamino-substituted-C.sub.1-4 alkyl ester of said acid, a phenyl-dimethylamino ester of said acid or a .alpha.-monoglyceride of said acid.The compounds of formulas I and II are useful as agents for the treatment of hyperproliferative skin diseases such as psoriasis.

Abstract: The invention relates to compounds of the formula ##STR1## wherein R.sub.1 is hydrogen or methyl; A is ##STR2## or A is ##STR3## wherein R.sub.2 is lower alkyl; R.sub.3 is phenyl, or phenyl substituted by 1 to 3 substituents selected from the group consisting of halo, lower alkyl, and lower alkoxy; and R.sub.4 is hydrogen or methyl or the corresponding hydroxy acid of formula ##STR4## wherein A is ##STR5## or A is ##STR6## and R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are as described above; or a pharmaceutically acceptable salt of said acid, a C.sub.1-4 alkyl ester of said acid, an acetylamino-substituted-C.sub.1-4 alkyl ester of said acid, a phenyl-dimethylamino ester of said acid or a .alpha.-monoglyceride of said acid.The compounds of formulas I and II are useful as agents for the treatment of hyperproliferative skin diseases such as psoriasis.