D-Serine (I) is nitrosated in the presence of bromide ion to give (R)-2-bromo-3-hydroxypropanoic acid (II), which is converted into (R)-2-hydroxy-3-(methylthio)propanoic acid (IV), via the epoxy acid (III), using sodium methoxide followed by sodium methanethiolate. This hydroxy acid (IV) is coupled to (S)-3-(acetylthio)-2-methylpropanoic acid using either the imidazolide or acid chloride. Final deprotection of 2(R)-[3-(acetylthio)-2(S)-methyl-1-oxopropoxy]-3-(methylthio)propanoic acid (V) is achieved using aqueous ammonia. FPL 66564 is conveniently isolated either as the 1-adamantanamine or L-lysine salt.