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For Dutch pharmaceutical company, see Synthon (company).

In retrosynthetic analysis, a synthon is a destructural[clarification needed] unit within a molecule which is related to a possible synthetic operation. The term was coined in 1968 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 1981 book, The Logic of Chemical Synthesis,[4] as it was not included in the index.


Retrosynthetic analysis of phenylacetic acid

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 reactant. 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
Synthesis of phenylacetic acid english.svg

Alternative use in Synthetic Oligonucleotides[edit]

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]


  1. ^ E.J. Corey (1967). Pure App. Chem. 14: 30–37 |url= missing title (help). 
  2. ^ E. J. Corey (1988). "Robert Robinson Lecture. Retrosynthetic thinking—essentials and examples". Chem. Soc. Rev. 17: 111–133. doi:10.1039/CS9881700111. 
  3. ^ 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. 
  4. ^ Elias James Corey, Xue-Min Cheng (1995). The logic of chemical synthesis. Wiley-Interscience. ISBN 0-471-11594-0. 
  5. ^ 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. Bibcode:2004PNAS..10115573K. doi:10.1073/pnas.0406911101.