A process for the manufacture of compounds of formula comprising the asymmetric hydrogenation of a compound of formula using a metal complex catalyst, wherein; R 1 is an amino-protecting group selected from the list of benzyl, benzyloxycarbonyl (carbobenzyloxy, CBZ), 9-Fluorenylmethyloxycarbonyl (Fmoc), p-methoxybenzyloxycarbonyl, p-nitrobenzyloxycarbonyl, tert-butoxycarbonyl, and trifluoroacetyl; and M is a metal ion selected from the list of alkali metal ion, alkaline earth metal ion and transition metal ion; wherein the metal complex catalyst is a ruthenium complex catalyst selected from a compound of formula, or: Ru 2 D (C 1) [Ru 2-p m] p Ru (E') wherein: D is a chiral phosphine ligand; L is a neutral ligand selected from C 2-7 alkene, cyclooctene, 1,3-hexadiene, norbornadiene, 1,5-cyclooctadiene, benzene, hexamethylbenzene, 1,3,5-trimethylbenzene, p-cymene, tetrahydrofuran, dimethylformamide, acetonitrile, benzonitrile, acetone, toluene and methanol; Z is an anionic ligand selected from hydride, fluoride, chloride, bromide, η 5 -2,4-pentadienyl, η 5 -2,4-dimethyl-pentadienyl or the group A-COO -, with the proviso that when two Z are attached to the Ru atom they can either be the same or different; A is C 1-7 alkyl, C 1-7 haloalkyl, aryl, or haloaryl; Y is a non-coordinating anion selected from fluoride, chloride, bromide, BF 4 -, ClO 4 -, SbF 6 -, PF 6 -, B(phenyl) 4 -, B(3,5-di-trifluoromethyl-phenyl) 4 -, CF 3 SO 3 -, and C 6 H 5 SO 3 -; F is an optionally chiral diamine; E and E' are both halogen ions, or E is hydride and E' is BH 4 -; m is 1, 2, 3 or 4; and p is 1 or 2. using a metal complex catalyst, wherein; R 1 is an amino-protecting group selected from the list of benzyl, benzyloxycarbonyl (carbobenzyloxy, CBZ), 9-Fluorenylmethyloxycarbonyl (Fmoc), p-methoxybenzyloxycarbonyl, p-nitrobenzyloxycarbonyl, tert-butoxycarbonyl, and trifluoroacetyl; and M is a metal ion selected from the list of alkali metal ion, alkaline earth metal ion and transition metal ion; R 1 is an amino-protecting group selected from the list of benzyl, benzyloxycarbonyl (carbobenzyloxy, CBZ), 9-Fluorenylmethyloxycarbonyl (Fmoc), p-methoxybenzyloxycarbonyl, p-nitrobenzyloxycarbonyl, tert-butoxycarbonyl, and trifluoroacetyl; and M is a metal ion selected from the list of alkali metal ion, alkaline earth metal ion and transition metal ion; wherein the metal complex catalyst is a ruthenium complex catalyst selected from a compound of formula, or: Ru 2 D (C 1) [Ru 2-p m] p Ru (E') wherein: D is a chiral phosphine ligand; L is a neutral ligand selected from C 2-7 alkene, cyclooctene, 1,3-hexadiene, norbornadiene, 1,5-cyclooctadiene, benzene, hexamethylbenzene, 1,3,5-trimethylbenzene, p-cymene, tetrahydrofuran, dimethylformamide, acetonitrile, benzonitrile, acetone, toluene and methanol; Z is an anionic ligand selected from hydride, fluoride, chloride, bromide, η 5 -2,4-pentadienyl, η 5 -2,4-dimethyl-pentadienyl or the group A-COO -, with the proviso that when two Z are attached to the Ru atom they can either be the same or different; A is C 1-7 alkyl, C 1-7 haloalkyl, aryl, or haloaryl; Y is a non-coordinating anion selected from fluoride, chloride, bromide, BF 4 -, ClO 4 -, SbF 6 -, PF 6 -, B(phenyl) 4 -, B(3,5-di-trifluoromethyl-phenyl) 4 -, CF 3 SO 3 -, and C 6 H 5 SO 3 -; F is an optionally chiral diamine; E and E' are both halogen ions, or E is hydride and E' is BH 4 -; m is 1, 2, 3 or 4; and p is 1 or 2. D is a chiral phosphine ligand; L is a neutral ligand selected from C 2-7 alkene, cyclooctene, 1,3-hexadiene, norbornadiene, 1,5-cyclooctadiene, benzene, hexamethylbenzene, 1,3,5-trimethylbenzene, p-cymene, tetrahydrofuran, dimethylformamide, acetonitrile, benzonitrile, acetone, toluene and methanol; Z is an anionic ligand selected from hydride, fluoride, chloride, bromide, η 5 -2,4-pentadienyl, η 5 -2,4-dimethyl-pentadienyl or the group A-COO -, with the proviso that when two Z are attached to the Ru atom they can either be the same or different; A is C 1-7 alkyl, C 1-7 haloalkyl, aryl, or haloaryl; Y is a non-coordinating anion selected from fluoride, chloride, bromide, BF 4 -, ClO 4 -, SbF 6 -, PF 6 -, B(phenyl) 4 -, B(3,5-di-trifluoromethyl-phenyl) 4 -, CF 3 SO 3 -, and C 6 H 5 SO 3 -; F is an optionally chiral diamine; E and E' are both halogen ions, or E is hydride and E' is BH 4 -; m is 1, 2, 3 or 4; and p is 1 or 2.