New process for the preparation of useful intermediates for the preparation of NEP inhibitors

A process for preparing a compound of formula (4) or a salt thereof: ** ** Formula wherein: R1 is hydrogen or a nitrogen protecting group; this process comprising: A) reacting a compound of formula (1) or a salt thereof: Formula ** ** wherein R1 is hydrogen or a nitrogen protecting group; with a catalyst of transition metal, optionally in the presence of a base to obtain the compound of formula (4) or a salt thereof, or B) reacting a compound of formula (3) or a salt ** ** Formula thereof wherein: R1 is hydrogen or a nitrogen protecting group; a selenide in the presence of a base to obtain a compound of formula (6) or a salt thereof,