The invention relates to a process for the optical resolution of a dibenzo[b,d]azepinone derivative of formula II, wherein R1 is hydrogen or halogen and R2 is either C1-4-alkyl optionally substituted with C3-7-cycloalkyl or benzyl which is optionally substituted with C1-4-alkoxy, to obtain a (S)-7-amino-5H,7H-dibenzo[b,d]azepin-6-one of formula I, wherein R1 is as in the compound of formula II. The (S)-7-amino-5H,7H-dibenzo[b,d]azepin-6-one of formula I can be used as a chiral building block for the preparation of malonamide derivatives which have the potential to act as gamma-secretase inhibitors and therefore may be useful in the treatment of Alzheimer's disease and cancer.
