“A reasonably stereospecific multistep conversion of Boc-protected alfa-amino acids to Phth-protected beta3-amino acids”

A method for the synthesis of b3-amino acids starting from a-amino acids is described. This conversion can be effected by an eight-step procedure which involves the transformation of the carboxylic group into an alkyne followed by a selenium-mediated conversion of the carbon–carbon triple bond to a Se-phenyl selenocarboxylate intermediate. The reactive Se-phenyl selenocarboxylate intermediates can be trapped with water, alcohols or the amine of an amino acid derivative to give b3-amino acids, b3-amino esters or mixed peptides, respectively. The whole transformations of the carboxylic group into an alkyne and of the alkyne group into b3-amino acids may not require purification of the intermediate products but a workup and isolation procedure of crude materials.