Synthon
A synthon is a concept in retrosynthetic analysis. It is defined as a structural unit within a molecule which is related to a possible synthetic operation. The term was coined in 1967 by E.J. Corey.[1] He noted in 1988 that the "word synthon has now come to be used to mean synthetic building block rather than retrosynthetic fragmentation structures".[2] It was noted in 1998 [3] that the phrase did not feature very prominently in Corey's 1995 book, The Logic of Chemical Synthesis,[4] as it was not included in the index.
[edit] Example
In planning the synthesis of phenylacetic acid, two synthons are identified: a nucleophilic "-COOH" group, and an electrophilic "PhCH2+" group. Of course, both synthons do not exist per se; synthetic equivalents corresponding to the synthons are reacted to produce the desired product. In this case, the cyanide anion is the synthetic equivalent for the -COOH synthon, while benzyl bromide is the synthetic equivalent for the benzyl synthon.
The synthesis of phenylacetic acid determined by retrosynthetic analysis is thus:
- PhCH2Br + NaCN → PhCH2CN + NaBr
- PhCH2CN + 2 H2O → PhCH2COOH + NH3
- C2 synthons - acetylene, acetaldehyde
- -C2H4OH synthon - ethylene oxide
- carbocation synthons - alkyl halides
- carbanion synthons - Grignard reagents, organolithiums, substituted acetylides
[edit] Alternative use in Synthetic Oligonucleotides
This term is also used in the field of gene synthesis—for example "40-base synthetic oligonucleotides are built into 500- to 800-bp synthons".[5]
[edit] References
- ^ E.J. Corey (1967). Pure App. Chem. 14: 30–37. http://www.iupac.org/publications/pac/pdf/1967/pdf/1401x0019.pdf.
- ^ E. J. Corey (1988). "Robert Robinson Lecture. Retrosynthetic thinking—essentials and examples". Chem. Soc. Rev. 17: 111–133. doi:10.1039/CS9881700111. http://pubs.rsc.org/en/Content/ArticleLanding/1988/CS/cs9881700111.
- ^ W.A. Smit, A.F. Buchkov, R.Cople (1998). Organic Synthesis, the science behind the art. Royal Society of Chemistry. ISBN 0-85404-544-9.
- ^ Elias James Corey, Xue-Min Cheng (1995). The logic of chemical synthesis. Wiley-Interscience. ISBN 0-471-11594-0.
- ^ Sarah J. Kodumal, Kedar G. Patel, Ralph Reid, Hugo G. Menzella, Mark Welch, and Daniel V. Santi (November 2, 2004). "Total synthesis of long DNA sequences: Synthesis of a contiguous 32-kb polyketide synthase gene cluster". PNAS 101 (44): 15573–15578. http://www.pnas.org/content/101/44/15573.long.
