Processes are disclosed for the preparation of (2S,3S,5S)-5-(N-(N-((N-Methyl-N-((2-isopropyl-4-thiazolyl)methyl)amino)carbonyl)-L-valinyl) amino)-2-(N-((5-thiazolyl)methoxycarbonyl)amino)-1,6-diphenyl-3-hydroxyhexane or an acid addition salt thereof and (2S,3S,5S)-5-(N-(N-((N-Methyl-N-((2-isopropyl-4-thiazolyl) methyl)amino)carbonyl)-D-valinyl)amino)-2-(N-((5-thiazolyl) methoxycarbonyl)amino)-1,6-diphenyl-3-hydroxyhexane or an acid addition salt thereof.