Convergent synthesis

In <a href="/facts/Chemistry/SrNqkGVm">chemistry</a> a convergent synthesis is a strategy that aims to improve the <a href="/facts/Efficiency/azCNkIzY">efficiency</a> of <a href="/facts/Multistep_synthesis/3KXsVVwC">multistep synthesis</a>, most often in <a href="/facts/Organic_synthesis/aprl6Iq7">organic synthesis</a>. In this type of synthesis several individual pieces of a complex molecule are synthesized in stage one, and then in stage two these pieces are combined to form the final product. In linear synthesis the overall <a href="/facts/Chemical_yield/fkBhd9dH">yield</a> 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 and involves fragment coupling and independent synthesis. This technique is more useful if the compound is large and symmetric, where at least two aspects of the molecule can be formed separately and still come together. 
Examples:

<ul><li>Convergent synthesis is encountered in <a href="/facts/Dendrimer/3aXUKBej">dendrimer</a> synthesis where branches (with the number of generations preset) are connected to the central core.</li>
<li>Proteins of up to 300 <a href="/facts/Amino_acid/WDxYwBny">amino acids</a> are produced by a convergent approach using <a href="/facts/Chemical_ligation/JFnI7gWJ">chemical ligation</a>.</li>
<li>An example of its use in <a href="/facts/Total_synthesis/3GGoqhBm">total synthesis</a> is the final step (<a href="/facts/Photochemical/GsXNBWon">photochemical</a> [2+2]<a href="/facts/Cycloaddition/Gme6TDFP">cycloaddition</a>) towards the compound biyouyanagin A:</li></ul>

Convergent synthesis open-in-new

Convergent synthesis