This invention provides compounds of the structure ##STR1## where R.sub.1 is C.sub.3 -C.sub.20 alkyl or arylalkyl; R.sub.2 is hydrogen, loweralkanoyl, loweralkylsulfonyl, loweralkoxycarbonyl, carbamoyl or ##STR2## wherein X is an alkylene group having from 2 to 4 carbon atoms; and R.sub.3 and R.sub.4 are the same or different members of the group consisting of hydrogen or loweralkyl, or R.sub.3 and R.sub.4 taken together form a 5-, 6-, or 7-member heterocyclic ring; and the pharmaceutically acceptable acid addition salts thereof. The compounds of this invention are useful as analgesics, tranquilizers and sedative-hypnotics.