Disclosed is a process for producing an aminoadamantane carbamate derivative which is useful as a significant intermediate of an 11βHSD-1 inhibitor.A process for producing an acid addition salt of a compound represented by the Formula (II):or a solvate of the acid addition salt, wherein R1 and R2 are each independently hydrogen, substituted or unsubstituted alkyl or the like R3 and R4 are each independently hydrogen, substituted or unsubstituted alkyl or the like and R5 and R6 are each independently hydrogen, halogen, carboxy, nitro, substituted or unsubstituted alkyl or the likewhich comprises separating an acid addition salt of a compound represented by the Formula (II) or a solvate of the acid addition salt by adding an acid to a mixture of syn isomer and anti isomer of a compound represented by the Formula (I):wherein R1, R2, R3, R4, R5, and R6 are as defined above, in the presence of a solvent.
