2-(Acyloxy)ethylphosphonate analogues of prenyl pyrophosphates: synthesis and biological characterization.

2-(Acyloxy)ethylphosphonate analogues of geranyl, farnesyl, and geranylgeranyl pyrophosphate have been prepared. Horner-Wadsworth-Emmons condensation of different terpene aldehydes with an unsymmetrical bisphosphonate was the key step in syntheses of the phosphonates bearing alpha,beta-unsaturated acyloxy groups. After preparation of the respective phosphonic acids through reaction with TMSBr, both acids and esters were tested for their effects on DNA synthesis in human-derived myeloid and lymphoid leukemia cell lines. The phosphonate esters varied substantially in their ability to impair proliferation of the different cell lines, but testing against one possible target, farnesyl protein transferase (FPTase), revealed little impact at concentrations ranging up to 10 microM. Because the corresponding 2,3-dihydro compounds showed similar biological activity, conjugate addition would not appear to be involved in the toxicity.

Phosphonate and bisphosphonate analogues of farnesyl pyrophosphate as potential inhibitors of farnesyl protein transferase.

Several phosphonate and bisphosphonate analogues of farnesyl pyrophosphate have been prepared for an examination of their ability to inhibit farnesyl protein transferase (FPTase). A Horner-Wadsworth-Emmons condensation of farnesal or geranial with tetraethyl methylenediphosphonate gave the desired vinyl phosphonates, while alkylation of the dimethyl methylphosphonate anion with a terpenoid bromide gave the corresponding saturated phosphonates. Alkylation of tetraethyl methylenediphosphonate with farnesyl bromide gave the expected alkyl bisphosphonate, which was converted to its alpha, beta-unsaturated derivative by preparation of the phenyl selenide, oxidation to the selenoxide, and elimination. In a similar fashion, triethyl phosphonoacetate was converted to a farnesyl pyrophosphate analogue by reaction with farnesyl bromide. After preparation of the respective acids, each compound was tested for inhibition of FPTase at concentrations ranging up to 10 microM. The effect of these compounds on FPTase activity varied substantially, ranging from depressed to surprisingly enhanced enzymatic activity.

Stereochemistry-dependent inhibition of RAS farnesylation by farnesyl phosphonic acids.

This investigation compares the effects of three farnesyl pyrophosphate analogs on selected aspects of isoprenoid metabolism. E,E-alpha-Hydroxyfarnesylphosphonate was prepared by an improved variation on a literature synthesis, which also gave access to the new Z,E-alpha-hydroxyfarnesyl- and alpha-hydroxygeranylphosphonates. A striking find is that only E,E-alpha-hydroxyfarnesylphosphonate induces alteration of RAS processing in intact human-derived leukemia cells and inhibits farnesyl protein transferase in enzyme assays, while the Z,E-alpha-farnesyl- and geranylphosphonates are inactive. The inhibitory activity of E,E-alpha-hydroxyfarnesylphosphonate is greater in enzyme than intact cell assays. This active compound does not significantly inhibit geranylgeranyl protein transferase I or squalene synthase, nor does it diminish cholesterol synthesis. These results indicate that the length of the terpenoid chain and olefin stereochemistry allow selective inhibition of critical enzymes of terpenoid metabolism. Discrimination was observed between inhibition of farnesyl protein transferase and squalene synthase by E,E-alpha-hydroxyfarnesylphosphonate, even though both enzymes utilize farnesyl pyrophosphate as their natural substrate.