the process of the invention is explained in detail in the following examples . a reductive amination according to patent application p 41 23 248 . 8 is carried out in analogy with example 3 , page 10 , therein . the reaction solution of a 150 mmole batch was largely evaporated in a vacuum at a 45 ° c . bath temperature . the residue was taken up in 750 ml water and briefly stripped in a vacuum . after the addition of 150 ml 1 , 1 , 1 - trichloroethane the ph was adjusted to 1 with conc . hcl . the mixture was agitated 10 min and the phases subsequently separated . the ph of the aqueous phase was adjusted to 4 . 6 , and it was extracted 2 × with 300 ml 1 , 1 , 1 - trichloroethane . the organic phase was evaporated in a vacuum and taken up in 250 ml methyl - tert . butyl ether . a thick crystalline pulp was produced by cooling off to 5 ° c . and seeding , which pulp was compounded after 5 hours under vigorous agitation with 65 ml methylcyclohexane . after a further 2 h at 5 ° c . the matter was removed by suction and dried in a vacuum . yield : 54 g ( 67 . 5 % of theoretical ), sss diastereomer content : & gt ; 99 %, [ α ] d 20 : - 25 . 6 ° [( c = 1 in meoh / hcl ( 1 : 1 )]. a reductive amination according to patent application p 41 23 248 . 8 is carried out in analogy with example 3 , page 10 , therein . the reaction solution of a 150 mmole batch was largely evaporated in a vacuum at a 45 ° c . bath temperature . the residue was taken up in 750 ml water and briefly stripped in a vacuum . after the addition of 120 ml toluene and 30 ml ethyl acetate the ph was adjusted to 1 with conc . hcl . the mixture was agitated 10 min and the phases subsequently separated . the ph of the aqueous phase was adjusted to 4 . 6 and it was extracted 1 × with 400 ml ethyl acetate . the organic phase was evaporated in a vacuum and taken up in 250 ml methyl - tert . butyl ether . a thick crystalline pulp was produced by cooling off to 5 ° c . and seeding , which pulp was compounded after 5 hours under vigorous agitation with 65 ml methylcyclohexane . after a further 2 h at 5 ° c . the matter was removed by suction and dried in a vacuum . yield : 54 g ( 68 % of theoretical ), sss diastereomer content : & gt ; 99 %, [ α ] d 20 : - 25 . 5 ° [( c = 1 in meoh / hcl ( 1 : 1 )].