| abstract |
A compound of formula I, wherein PROT is an amine protecting group and PROT' is hydrogen, or PROT and PROT' together with their attached nitrogen atoms form a heterocycle as an amine protecting group, and PROT'' is a mercapto protecting group; processes for the preparation of said compounds; intermediates in the preparation of said compounds and the preparation of intermediates in stereoisomerically pure form; and the use of said compounds in the preparation of pharmaceutically active compounds, . |