Process for the production of a .beta.-amino alcohol

Process for the production of 2-›3-(S)-amino-2(R)-hydroxy-4-phenylbutyl!-N-tert.-butyl-decahydro-(4aS,8a S)-isoquinoline-3(S)-carboxamide of the formula ##STR20## characterised in that a) L-phenylalanine of the formula ##STR21## is reacted with phthalic anhydride, b) the resultant 3-phenyl-2(S)-phthalimidopropionic acid of the formula ##STR22## is converted into the corresponding acid chloride, c) the resultant 3-phenyl-2(S)-phthalimidopropionic acid chloride of the formula ##STR23## is reduced, d) the resultant 3-phenyl-2(S)-phthalimidopropan-1-al of the formula ##STR24## is transformed into the 1-cyano-3-phenyl-2(S)-phthalimidopropan-1-ol of the formula ##STR25## e) the resultant nitrile of the formula VI is hydrolysed, f) the unisolated 3(S)-amino-2-hydroxy-4-phenylbutyric acid formed of the formula ##STR26## is reacted with a low alkyl ester or the phenyl or benzyl ester of chloroformic acid,

• g) a resultant 3(S)-›low alkoxycarbonylamino-, phenyloxycarbonylamino- or benzyloxycarbonxylamino!-2-hydroxy-4-phenylbutyric acid of the general formula ##STR27## in which R means low alkyl, phenyl or benzyl, is cyclised, h) the resultant crystallized (4S,5S)-4-benzyl-2-oxo-oxazolidine-5-carboxylic acid of the formula ##STR28## is esterified with a low alkanol, i) the resultant (4S,5S)-4-benzyl-2-oxo-oxazolidine-5-carboxylic acid low alkyl ester of the general formula ##STR29## in which R.sup.1 means low alkyl, is reduced j) the resultant (4S,5S)-4-benzyl-5-hydroxymethyl-oxazolidin-2-one of the formula ##STR30## is reacted in the presence of a base with a sulphonic acid chloride of the general formula
• R.sup.2 --SO.sub.2 Cl
• in which R.sup.2 means low alkyl, phenyl or phenyl mono- or disubstituted by halogen, low alkyl or nitro,
• k) a resultant sulphonic acid ester of the general formula ##STR31## in which R.sup.2 has the above-stated meaning, is reacted in the presence of a base with N-tert.-butyl-decahydro-(4aS,8aS)-isoquinoline-3(S)-carboxamide of the formula ##STR32## and l) the resultant 2-›(4S,5R)-4-benzyl-2-oxo-oxazolidin-5-yl methyl!-N-tert.-butyl-decahydro-(4aS,8aS)-isoquinoline-3(S)-carboxamide of the formula ##STR33## is treated with a base.