To provide an intermediate useful for synthesizing a compound of chemical formula I.

This intermediate is an amine compound of formula (IVd) (wherein Ar2a is phenyl, pyridyl or thienyl; X is H, a halo or 1-7C alkoxy; R1 is H, an optionally protected hydroxy or 1-4C alkyl; and R2 and R3 are each H, OH or a 1-7C alkyl optionally substituted with halo(s)).