Isoprenoids constitute the largest class of natural products with greater than 55,000 identified members. They play essential
roles in maintaining proper cellular function leading to maintenance of human health, plant defense mechanisms against predators, and
are often exploited for their beneficial properties in the pharmaceutical and nutraceutical industries. Most impressively, all known isoprenoids
are derived from one of two C5-precursors, isopentenyl diphosphate (IPP) or dimethylallyl diphosphate (DMAPP). In order to study
the enzyme transformations leading to the extensive structural diversity found within this class of compounds there must be access to the
substrates. Sometimes, intermediates within a biological pathway can be isolated and used directly to study enzyme/pathway function.
However, the primary route to most of the isoprenoid intermediates is through chemical catalysis. As such, this review provides the first
exhaustive examination of synthetic routes to isoprenoid and isoprenoid precursors with particular emphasis on the syntheses of intermediates
found as part of the 2C-methylerythritol 4-phosphate (MEP) pathway. In addition, representative syntheses are presented for the
monoterpenes (C10), sesquiterpenes (C15), diterpenes (C20), triterpenes (C30) and tetraterpenes (C40). Finally, in some instances, the synthetic
routes to substrate analogs found both within the MEP pathway and downstream isoprenoids are examined.