Isoprenoid analog compounds and methods of making and use thereof

The invention provides compounds of formula I: wherein X, R1, R2, and n have any of the values defined in the specification, and their pharmaceutically acceptable salts. The compounds are useful, for example, for blocking prenylation transferase enzymes, for probing or diagnosing protein prenylation processes, and for treating cancer in a mammal. The invention also provides pharmaceutical compositions, processes for preparing compounds of formula I, and intermediates useful for the synthesis of compounds of formula I.