AbstractTo prepare novel derivatives of naturally bioactive 3β‐hydroxy‐urs‐12‐en‐28‐oic acid (ursolic acid) with unusual properties and broad spectrum of activities, a number of chemical reactions were conducted. First, a variety of α‐aminophosphonates were prepared by a series of reactions involving the three‐component Mannich type reaction as a key step. Second, an array of phosphonodipeptides and their homologs was synthesized through multistep reactions including condensation of phthalic anhydride with glycine or β‐alanine, chlorination of N‐blocked amino acids, coupling of acid chloride with α‐aminophosphonates and sequential hydrazinolysis. Finally, new classes of phosphonodipeptide conjugates of ursolic acid and their homologs were obtained by condensation of 3β‐acetoxy‐urs‐12‐en‐28‐oyl chloride with phosphonodipeptides and their homologs. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:55–65, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20396