= Polyene cyclization
A <polyene cyclization> converts a chain containing several <carbon>–<carbon> double bonds into one or more rings. A suitable initiating event can generate a reactive centre that attacks a later double bond, producing another reactive centre and allowing a cascade of ring closures.
The folded chain's geometry helps determine which rings and <stereogenic centres> form. In biosynthesis, enzyme-controlled cyclization of precursors related to <squalene> constructs complex <steroid> frameworks. The double bonds need not all belong to one continuous conjugated system. A plausible drawn cascade also needs compatible reaction kinetics and a three-dimensional conformation; connectivity alone does not guarantee that a proposed sequence occurs.
Back to article page
