Chaetomellic acids are a class of alkyl dicarboxylic acids that were isolated from Chaetomella acutiseta. They are potent and highly specific farnesyl-pyrophosphate (FPP) mimic inhibitors of Ras farnesyl-protein transferase. We have previously described the first biogenetic type aldol condensation-based total synthesis of chaetomellic acid A. Modification of the later steps of that synthesis resulted in the efficient syntheses of chaetomellic acids A and B in three steps with 75-80% overall yield. In this report, details of the original total syntheses of chaetomellic acids A, B and C, the new syntheses of acids A and B and structure-activity relationship of these compounds against various prenyl transferases including human and yeast FPTase and bovine and yeast GGPTase I are described. Chaetomellic acids are differentially active against human and yeast FPTase. Chaetomellic acid A inhibited human and yeast FPTase activity with IC50 values of 55 nM and 225 microM, respectively. In contrast, chaetomellic acid C showed only a 10-fold differential in inhibitory activities against human versus yeast enzymes. In keeping with molecular modeling-based predictions, the compounds with shorter alkyl side chains (C-8) were completely inactive against FPTase.