A compound of the formula I:
##STR1##
in which
P is hydrogen or alkyl;
Y and Y' are each hydrogen or, when taken together, represent a group
.dbd.CH.sub.2 ;
W and W' are each hydrogen;
X is selected from the group consisting of a hydroxyalkyl, a hydroxyalkoxy,
an alkoxy optionally comprising an epoxide function, a hydroxyalkene, a
hydroxyalkadiene, a hydroxyalkyne and isomeric forms thereof; and
a) either R.sub.1 and R.sub.3 or R'.sub.3 form a saturated 5- or 6-membered
carbocyclic ring and R.sub.2, R'.sub.2, R.sub.3 or R'.sub.3, R.sub.4,
R'.sub.4, R.sub.5 and R'.sub.5 are each independently hydrogen or alkyl;
or
b) R.sub.2 or R'.sub.2 and R.sub.4 or R'.sub.4 form a saturated 5- or
6-membered carbocyclic ring, and R.sub.1, R.sub.2 or R'.sub.2, R.sub.3,
R'.sub.3, R.sub.4 or R'.sub.4, R.sub.5 and R'.sub.5 are each independently
hydrogen or alkyl; or
c) R.sub.3 or R'.sub.3 and R.sub.5 or R'.sub.5 form a saturated or
unsaturated 5- or 6-membered carbocyclic ring, and R.sub.1, R.sub.2,
R'.sub.2, R.sub.3 or R'.sub.3, R.sub.4, R'.sub.4, and R.sub.5 or R'.sub.5
are each independently hydrogen or alkyl; or
d) R.sub.3 or R'.sub.3 taken at the same time with R.sub.1 and R.sub.5 or
R'.sub.5 form a saturated 8- or 12-membered carbobicyclic ring, and
R.sub.2, R'.sub.2, R.sub.3 or R'.sub.3, R.sub.4, R'.sub.4, and R.sub.5 or
R'.sub.5 are each independently hydrogen or alkyl.
