Method for treating multiple sclerosis

A method of treating multiple sclerosis in a mammal in need of such treatment which comprises administering to said mammal a therapeutically effective amount of a compound, or a pharmaceutically acceptable salt thereof, of formula (I) ##STR19## wherein:

• R.sup.1 and R.sup.2 are each independently hydrogen, C.sub.3 -C.sub.6 alkyl, C.sub.1 -C.sub.6 alkoxy or
• R.sup.3 and R.sup.4 are each independently hydrogen or C.sub.1 -C.sub.4 alkyl;
• n is an integer from 0 to 4, both inclusive;
• and
• R.sup.5 and R.sup.6 are each independently hydrogen, C.sub.1 -C.sub.8 alkyl, C.sub.3 -C.sub.8 cycloalkyl, C.sub.2 -C.sub.8 alkenyl, C.sub.2 -C.sub.8 alkynyl, --(CH.sub.2).sub.q OR.sup.7, --(CH.sub.2).sub.q N(R.sup.7 R.sup.8), --(CH.sub.2).sub.q SR.sup.7, --(CH.sub.2).sub.r naphthyl or ##STR20## where q is an integer from 1 to 6, both inclusive, R.sup.7 and R.sup.8 are each independently hydrogen or C.sub.1 -C.sub.4 alkyl, R.sup.9 is hydrogen, halo, C.sub.1 -C.sub.4 alkyl, trifluoromethyl, hydroxy, amino, C.sub.1 -C.sub.4 alkylamino, di(C.sub.1 -C.sub.4 alkyl)amino, phenylamino or diphenylamino, and r is an integer from 0 to 4, both inclusive.