Synthesis of conformationally constrained hydroxy-alpha-amino acids by intramolecular conjugate addition.

An efficient and easily applicable method for the synthesis of a variety of hydroxy-alpha-amino acids analogues of serine and phenylalanine has been established. The method involves the stereoselective intramolecular conjugate addition of the benzamide group to cyclohexenone promoted by Lewis acid. Subsequent transformations of functional groups provide the conformationally constrained 2-hydroxy- and 2,4-dihydroxy-6-phenylcyclohexane-alpha-amino acids.