Editing Semisynthesis (section)

{{Short description|Type of chemical synthesis}}
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'''Semisynthesis''', or '''partial chemical synthesis''', is a type of [[chemical synthesis]] that uses [[chemical compound]]s isolated from [[natural source]]s (such as [[microbiology|microbial]] cell cultures or [[plant]] material) as the starting materials to produce novel compounds with distinct chemical and medicinal properties. The novel compounds generally have a high [[molecular weight]] or a complex molecular structure, more so than those produced by [[total synthesis]] from simple starting materials. Semisynthesis is a means of preparing many medicines more cheaply than by total synthesis since fewer chemical steps are necessary.

[[Image:Semisynthese taxol.svg|thumb|right|400px|alt=|'''Semisynthesis of [[paclitaxel]]'''. Installation of the necessary side chain and acetyl group of paclitaxel by a short series of steps, starting from isolated 10-deacetylbaccatine III.<ref name=Goodman/>]]
[[Image:ArtemetherSynthesis.png|thumb|right|400px|alt=|An undesirable [[lactone]] ring in [[artemisinin]] is replaced by an [[acetal]] by [[organic reduction|reduction]] with [[potassium borohydride]], followed by [[methoxy]]lation.<ref name=BoehmOPRD07/>]]

Drugs derived from natural sources are commonly produced either by isolation from their natural source or, as described here, through semisynthesis of an isolated agent. From the perspective of [[chemical synthesis]], [[living organisms]] act as highly efficient chemical factories, capable of producing structurally complex compounds through [[biosynthesis]]. In contrast, engineered chemical synthesis, although powerful, tends to be simpler and less chemically diverse than the complex biosynthetic pathways essential to life.