the invention provides a process for preparing compounds , as a single enantiomer or mixture of enantiomers , represented by the formula : ## str1 ## in which : x and y are independently hydrogen , hydroxy , lower alkyl , lower alkoxy or halo , or x and y taken together is methylenedioxy or ethylene - 1 , 2 - dioxy , and z is -- so 2 r or -- cnr 3 r 4 , in which ; r is lower alkyl , optionally substituted phenyl , -- m or 1 or -- nr 1 r 2 wherein m is an integer of 1 to 6 and r 1 and r 2 are independently hydrogen or lower alkyl ; and r 3 and r 4 are independently hydrogen , alkyl , optionally substituted phenyl or phenyl lower alkyl ; or r 1 and r 2 taken together with the nitrogen to which they are attached or r 3 and r 4 taken together with the nitrogen to which they are attached represent a heterocycle of the formula : ## str2 ## wherein a is -- ch 2 --, -- nr 1 -- or oxygen ; and novel intermediates .