摘要:
A compound of Formula (I) ##STR1## or a pharmaceutically acceptable salt thereof, wherein n is an integer between 2 and 6 and R.sub.1 is a methyl group or a group ##STR2## wherein R.sub.2, R.sub.3 and R.sub.4 are independently hydrogen, hydroxy, methoxy, methylsulfonyl, or one of R.sub.2, R.sub.3 and R.sub.4 together with another one of the three substituents forms a --O--CH.sub.2 --O-- bridge. The asterisk marks an asymmetric carbon atom.