Abstract: Levorotatory enantiomers of the derivatives of 5,6,13,13a-tetrahydro-8H-dibenzo-[a,g]-quinolizine of formula III ##STR1## wherein R'.sub.3 is hydrogen, an aryl or alkyl group or a --OR or --SR moiety wherein R is hydrogen, an aryl or alkyl group or a group of formula: ##STR2## wherein R" is an aryl or alkyl group, R'.sub.10 and R'.sub.11 which are identical or different, represent hydrogen, an aryloxy, alkoxy or hydroxy group or R'.sub.10 and R'.sub.11 taken together form a --O--(CH.sub.2).sub.n --O-- group in which n is 1 to 3.Application to treatment of cardiovascular disorders.