Organic synthesis



Organic synthesis is a special branch of total synthesis and methodology.

Total synthesis

Main article: Total synthesis

A total synthesis[1] is the complete convergent synthesis is often preferred. This is where several "pieces" (key intermediates) of the final product are synthesized separately, then coupled together, often near the end of the synthesis.

The "father" of modern organic synthesis is regarded as Danishefsky's synthesis of Taxol.

Methodology

Each step of a synthesis involves a chemical reaction, and reagents and conditions for each of these reactions need to be designed to give a good yield and a pure product, with as little work as possible[3]. A method may already exist in the literature for making one of the early synthetic intermediates, and this method will usually be used rather than "trying to reinvent the wheel". However most intermediates are compounds that have never been made before, and these will normally be made using general methods developed by methodology researchers. To be useful, these methods need to give high yields and to be reliable for a broad range of substrates. Methodology research usually involves three main stages- discovery, optimisation, and studies of scope and limitations. The discovery requires extensive knowledge of and experience with chemical reactivities of appropriate reagents. Optimisation is where one or two starting compounds are tested in the reaction under a wide variety of conditions of temperature, solvent, reaction time, etc., until the optimum conditions for product yield and purity are found. Then the researcher tries to extend the method to a broad range of different starting materials, to find the scope and limitations. Some larger research groups may then perform a total synthesis (see above) to showcase the new methodology and demonstrate its value in a real application.

Asymmetric synthesis

Main article: Chiral synthesis

Many complex natural products occur as one pure chiral resolution.

In the latter half of the twentieth century, chemists began to develop methods of asymmetric Robert B. Woodward and new developments in synthetic methodology, chemists became more able to take simple molecules through to more complex molecules without unwanted racemisation, by understanding stereocontrol. This allowed the final target molecule to be synthesised as one pure enantiomer without any resolution being necessary. Such techniques are referred to as asymmetric synthesis.

Synthesis design

computational chemistry, James B. Hendrickson, who developed a computer program for designing a synthesis based on sequences of generic "half-reactions". Computer-aided methods have recently been reviewed.[5]

See also

References

  1. ^ Nicolaou, K. C.; Sorensen, E. J. (1996). Classics in Total Synthesis. New York: VCH. 
  2. ^ Journal of the American Chemical Society 76 (18): 4749–4751.
  3. ^ March, J.; Smith, D. (2001). Advanced Organic Chemistry, 5th ed. New York: Wiley. 
  4. ^ Corey, E. J.; Cheng, X-M. (1995). The Logic of Chemical Synthesis. New York: Wiley. 
  5. ^ Todd, Matthew H. (2005). "Computer-aided Organic Synthesis" (PDF subscription required). Chemical Society Reviews 34: 247–266.
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Organic_synthesis". A list of authors is available in Wikipedia.