Farnesylation is a posttranslational lipid modification in which a 15-carbon farnesyl isoprenoid is linked via a thioether bond to specific cysteine residues of proteins in a reaction catalyzed by protein farnesyltransferase (FTase). We synthesized analogues (3-6) of farnesyl pyrophosphate (FPP) to probe the range of modifications possible to the FPP skeleton which allow for efficient transfer by FTase. Photoaffinity analogues of FPP (5, 6) were prepared by substituting perfluorophenyl azide functional groups for the omega-terminal isoprene of FPP. Substituted anilines replace the omega-terminal isoprene in analogues 3 and 4. Compounds 3-5 were prepared by reductive amination of the appropriate anilines with 8-oxo-geranyl acetate, followed by ester hydrolysis, chlorination, and pyrophosphorylation. Additional substitution of three methylenes for the beta-isoprene of FPP gave photoprobe 6 in nine steps. Preparation of the analogues required TiCl(4)-mediated imine formation prior to NaBH(OAc)(3) reduction for anilines with a pK(a) < 1. The azide moiety was not affected by Ph(3)PCl(2) conversion of allylic alcohols 13-16 into corresponding chlorides 17-20. Analogues 3-6 are efficiently transferred to target N-dansyl-GCVLS peptide substrate by mammalian FTase. Comparison of analogue structures and kinetics of transfer to those of FPP reveals that ring fluorination and para substituents have little effect on the affinity of the analogue pyrophosphate for FTase and its transfer efficiency. These results are also supported with models of the analogue binding modes in the active site of FTase. The transferable azide photoprobe 5 photoinactivates FTase. Transferable analogues 5 and 6 allow the formation of appropriately posttranslationally modified photoreactive peptide probes of isoprene function.

The simple fullerene diols C(60)(OH)(2) and C(70)(OH)(2) were prepared by addition of RuO(4) followed by acid hydrolysis. The 1,2-C(60)(OH)(2) isomer was formed from C(60), and two isomers (1,2 and 5,6) of C(70)(OH)(2) were formed in the RuO(4) hydroxylation of C(70). These compounds are much more soluble in THF and dioxane than the parent fullerenes. More highly hydroxylated materials are formed as well.

The total synthesis of the HMG-CoA synthase inhibitor 1233A (1), starting from either (fi)-pulegone (6) or diketo ester 12, is described. The key transformations included the diastereoselective [2,3] rearrangements of allylic ethers 9 and 19 to alcohols 10 and lib, respectively, and the diastereoselective hydroboration of 1 lb to form 19. A Pd-mediated coupling of iodo olefin 31a with tert-butyl crotonate under newly devised conditions provides an efficient preparation of the diene portion of 1233A.

No abstract