"Semisynthesis" or partial chemical synthesis is a type of chemical synthesis that uses compounds isolated from natural sources (for example plant material or bacterial or cell cultures) as starting materials. These natural biomolecules are usually large and complex molecules. This is opposed to a total synthesis where large molecules are synthesized from a stepwise combination of small and cheap (petrochemical) building blocks. Semisynthesis is usually used when the precursor molecule is too st… (More on Semisynthesis)