Patent ID: 7714157

Claim:
An optically active compound of the formula (1a): wherein R 10 is a substituted or unsubstituted alkyl or aryl group, R 11 is a protecting group for an amino group, R 12 is a protecting group for an amino group, or a hydrogen atom, R 13 is a substituted or unsubstituted alkyl group, or either R 11 or R 12 and R 13 are taken together to form a protecting group for amino acid, n 11 , n 12 and n 13 are each independently an integer of 0 or 1, the carbon atom marked with * is an asymmetric carbon atom, provided that R 10 is not a trifluoromethyl group, a nonafluorobutyl group or a pentafluorophenyl group.