Improved large-scale synthesis of phenylisoserine and the taxol C-13 side chain

Dihydrodihydroxycinnamic acids and their esters react with acetonitrile or benzonitrile in the presence of sulfuric acid to afford the corresponding syn-β-amino-α-hydroxypropionic acid derivatives. High yields and diastereoselectivity of this transformation allows preparation of various phenylisoserine derivatives on a practical scale.