Patent ID: 7557240

Claim:
A process for preparing optically active alkylsuccinic acid monoalkyl esters of the formula (I) where D and E are independently of one another H, C 1 -C 10 alkyl, R is C 1 -C 10 alkyl, aryl or alkylaryl, which comprises enantioselective hydrogenating a compound of the formula (II) where D, E and R have the abovementioned meanings, in the presence of a catalyst that has Rh, Ru or Ir as a metal atom which includes a phospholane ligand of the formula (L) where: R 1 and R 2 are independently of one another C 1 -C 6 alkyl, aryl, alkylaryl, R 1 is additionally hydrogen, A is either R 1 or with B=a linker with 1-5 C atoms between the two P atoms or Cp-Fe-Cp.