The regioselective opening reaction of 2,3-epoxyamides with various nucleophiles offers a variety of β-hydroxyamides with diverse synthetic utility depending on the introduced nucleophile. Due to the exclusive stereoselectivity in the formation of trans epoxyamides in reactions of aldehydes with stabilized sulfur ylides, we studied the isomerization of trans epoxyamides into the cis isomers with the objective of obtaining the corresponding syn opening products, which together with the anti isomers represent a variety of enantiomerically pure building blocks.