Racemic 3-IPHPC (2-hydroxy-3-imidazo[1,2-a]pyridine-3-yl-2phosphonopropionic acid) was prepared and characterized as described previously [32, 33] and stored at ,0uC and pH $7 [32, 33] . The purity was $98%by 1 H NMR. The inhibitor was tested in this work as the racemate [32, 33] . It was subsequently demonstrated that the individual enantiomers have markedly different IC 50 and Ki values for inhibition of Rab1a prenylation, thus the racemate value obtained here probably represents an upper limit with respect to the potency of the more active stereoisomer.