Convenient Preparation of Optically Active N,N’-Disubstituted Piperazines from Various (S)-α-Amino Acid Esters - Watanabe, Masaaki; Kojima, Yoshitane; Kawabe, Kenji; Hatamoto, Eiji; Tsuru, Eiji; Miyake, Hiroyuki; Yamashita, Tetsushi (Synthesis, 1996)