AIDS-144924 AIDS144924 NSC668449 Triethyl 21-(((benzyloxy)carbonyl)amino)-6,9,12,15,18-pentakis(3-ethoxy-3-oxopropyl)-5,8,11,14,17,20-hexaoxo-4,7,10,13,16,19-hexaazatricosane-1,3,23-tricarboxylate