Abstract: The synthetic production of cis-1,4-polyisoprene and other cis-1,4-polydienes is achieved by adding isoprene or other diene monomers to a natural rubber latex or washed rubber particles and utilizing various allylic pyrophosphate compounds. The natural rubber latex or washed rubber particles inherently contain an enzyme catalyst and desirably divalent metal cofactors therein and the polymerization can occur over a relatively wide temperature range. The process is believed to be a living carbocationic polymerization. The in vitro produced natural rubber polymers can contain from about 5 to about 30,000 repeat units and are essentially free of non-enzyme catalysts. The invention can be utilized to synthesize polyisoprenoids and precursors to form terpenes, vitamins, steroids, alkaloids, and the like.