Abstract: A compound of the formula: ##STR1## wherein R.sup.1 is a lower alkyl group; R.sup.2 is a hydrogen atom or an alkyl or alkenyl group which may be substituted; R.sup.3 and R.sup.4 each independently means a lower alkyl or lower alkoxy group or, taken together, mean a butadienylene group; and X.sup.1 and X.sup.2 each means a free hydroxy group or an esterified or etherified hydroxy group, has nerve growth factor secretion inducing activity, and a mammal suffering from degenerative nervous system disorders such as senile dementia, Alzheimer's disease, etc. is treated by administering said compound to said mammal.