Synthesis and pharmacological properties of new potent direct activators of heterotrimeric G proteins are described. Compounds were synthesized from protected amino acids with alkylamines using coupling reagents (CDI, DCC, and EDC). Alkyl-substituted amino acid amides and their corresponding di-and triamines were subjected to structure-activity analysis. All compounds activated membrane-bound HL-60 GTPases in a pertussis toxin- ...