Process for the preparation of a compound of formula Iin the form of a single stereoisomer in crystalline form, comprising deprotecting the amine group in a compound of formula IIaor in a mixture of a compound of formula IIa with a compound of formula IIband isolating a compound of formula I from the reaction mixture； compounds and salts of compounds of formula I in crystalline form； pharmaceutical compositions comprising such salts； processes for the preparation of intermediates and intermediates in a process for the preparation of a compound of formula I.
