Modification of the Aryl Ring

Acknowledgment. We acknowledge the Food and Drug Administration (Grant F D 00590) for their support of this investigation. M.K. thanks the Mitsubishi-Kasei Institute of Life Sciences for enabling him to perform this work. We also thank Constance Mullin for her help in preparing this manuscript. L-Aspartyl-L-m,p-dimethoxyphenylalanine Methyl Ester (20). The coupling reaction followed general procedure B. The residue obtained from removal of the solvent under reduced pressure was crystallized from isopropyl alcohol to give N-(benzyloxycarbony1)-Pbenzyl-L-aspartyl-L-m,p-dimethoxyphenylalanine methyl ester as a white solid (61%): mp 154-155 "C; [0IED $41.4" (c 1.0, CHC13). Anal. (C31H34N209) C , H, N. The deprotection reaction followed general procedure D. Removal of the solvent under reduced pressure yielded 20 as a