Alkanolamine derivatives and their optical isomers of the formula: ##STR1## wherein: N IS 2 OR 3, ANDR.sub.1 and R.sub.2 are lower alkyl or taken together with the nitrogen to which they are bonded, they form pyrrolidinyl, piperidino, dimethyl piperidino, morpholino, 1-thiomorpholino, azabicyclo [3, 3, 0] octyl or azabicyclo [3, 2, 2] nonyl.These compounds are used as medicines especially in the treatment of obesity, atheroma or metabolic diseases requiring weight reduction and regulation.