Subsequent treatment of compound 34 with sodium hydride, followed by reaction with propargyl bromide, gave the desired acetylene 14. The incorporation of the methyl group allowed preparation of a POM-prodrug, which displayed a 10-fold increase in cellular activity compared to the corresponding salt. These studies form the basis for future preclinical studies investigating the anti-myeloma activity of these novel -methyl triazole bisphosphonates. anti-cancer activity as well as antiparasitic activity, there is interest in the further development of FDPS inhibitors.2,3 While GGDPS Mosapride citrate inhibitors have not yet been examined in clinical trials, these agents also have potential as anti-cancer therapies.2,4,5 We have focused on the utility of GGDPS inhibitors as anti-myeloma agents. Inhibitors of GGDPS, by virtue of their ability to disrupt Rab GTPase geranylgeranylation, impair protein trafficking processes. This in turn can result in induction of the unfolded protein response pathway and ultimately apoptosis.6,7 Recently, our efforts to develop potent and selective GGDPS inhibitors have focused on triazole bisphosphonates that carry isoprenoid chains.5 Structure-function analysis has revealed that the chain length of the alkyl substituent as well as the olefin stereochemistry affects inhibitory activity.8C11 When the activity of triazoles derived from 10-carbon (i.e. 1 C 3) vs 11-carbon (i.e. 4 C 6) vs 12-carbon azides (i.e. 7 and 8) has been compared, the 11-carbon derivatives (i.e., homogeranyl and homoneryl) have shown the most potent GGDPS inhibitory activity. In addition, for any given chain length in this set of compounds, the isomers for the homogeranyl length (5) is more potent than either isomer alone, and further studies demonstrated that the two isomers interact in a synergistic manner to inhibit the target enzyme.10 To enhance cell uptake preparation of a prodrug form of the bisphosphonate might be advantageous,12 but efforts to secure a prodrug form of compound 5 have been frustrated, Mosapride citrate at least in part, because of the acidity of the -position. To circumvent this issue, it became important to determine whether incorporation of an alkyl substituent in the -carbon position could preserve the activity of these providers as GGDPS inhibitors. Here we statement the synthesis and biological activity of a PROCR novel group of -methylated isoprenoid triazole bisphosphonates. 2. Synthesis Our initial goal was to prepare a tetra pivaloyloxymethyl (POM)13 derivative of the active agent 5, because this combination showed attractive potency as the sodium salt9 and a prodrug can display enhanced potency in cellular bioassays.14,15 Such acyloxy derivatives of phosphonic acids are best prepared by treatment of the corresponding methyl ester having a reactive alkylating agent like POMCl,12 and it is conceivable the POM groups could be introduced at several different stages of the synthesis. As demonstrated in Plan 1, commercial tetramethyl methylenebisphosphonate (9) could be readily converted to the olefin 10 under standard conditions,16 and the subsequent reaction with POMCl offered the tetra POM compound 11 in a reasonable yield.12 However, attempts to convert this olefin to a terminal acetylene appropriate for a click reaction,17 which ultimately would lead to the triazole 12, went unrewarded presumably because of competing reaction with the POM organizations. Introduction of the alkyne could be accomplished by conjugate addition of sodium acetylide to the tetramethyl ester 10. In this process the desired adduct 13 usually was accompanied by a significant amount of the methylated product 14, and separation of these two compounds was not readily accomplished. Treatment of the combination with foundation and methyl iodide did result in clean conversion to the methylated compound 14, and this alkyne does undergo click reactions under standard conditions to give the expected product 15. Unfortunately, attempts to convert the tetramethyl ester 15 to the POM compound Mosapride citrate were not successful, maybe because the triazole system reacts with POMCl. Open in a separate window Plan 1 Attempted preparation of a triazole bisphosphonate prodrug. Preparation of the prospective compound 12 proved demanding through both of the reaction sequences explained above, and so it was decided to determine whether an -methyl group would have a significant impact on the biological activity of a triazole bisphosphonate before going after preparation of a POM prodrug. If -methylation could improve, or even simply maintain, the activity of the related bisphosphonates, it would eliminate concerns concerning the acidic -hydrogen and allow more options for synthetic sequences to prodrug forms. Consequently, we turned to our small library Mosapride citrate of triazole bisphosphonates and prepared a set of methylated Mosapride citrate analogues. Methylation of the C10 compounds proved to be straightforward as demonstrated in Plan 2. Upon treatment with sodium hydride followed by methyl iodide, the E/Z-mixture (16) as well as the individual Z- (17) and E-isomers (18) all undergo methylation smoothly, and the methylated products 19, 20,.