Convergent synthesis

In chemistry a convergent synthesis is a strategy that aims to improve the efficiency of multi-step chemical synthesis. In linear synthesis the overall yield quickly drops with each reaction step:


 * A → B → C → D

Suppose the yield is 50% for each reaction, the overall yield of D is only 12.5% from A.

In a convergent synthesis


 * A → B (50%)
 * C → D (50%)
 * B + D → E (25%)

the overall yield of E (25%) looks much better. Convergent synthesis is applied in the synthesis of complex molecules (see total synthesis) and involve fragment coupling and independent synthesis.

Examples:
 * Convergent synthesis is encountered in dendrimer synthesis where branches (with the number of generations preset) are connected to the central core
 * Proteins of up to 300 amino acids are produced by a convergent approach using chemical ligation.
 * An example of its use in total synthesis is the final step (photochemical [2+2]cycloaddition) towards the compound Biyouyanagin A :
 * [[Image:BiyouyanaginATotalSynthesis.png|400px|Final step in total synthesis of Biyouyanagin A with acetonaphthone photosensitizer]]