Triphenylmethyl group

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Blue- marked triphenylmethyl group in trityl chloride (top left), a trityl ether (top right) and N -trityl-protected glycine (bottom). (Ph = phenyl group )

The triphenylmethyl group is briefly referred to as the trityl radical in organic chemistry . It is often used as a protective group within organic synthesis strategies to prevent undesired conversions of free amines . The main area of ​​application is the construction of peptides from protected amino acids .

Triphenylmethyl radical (Gomberg radical) is a mesomeric stabilized , unusually stable radical.

It was discovered by Moses Gomberg in 1900 as an early example of organic reactive intermediate stages, which were followed by others ( Ketene 1905 by Hermann Staudinger ). Gomberg, who showed that triphenylmethyl chloride and zinc formed a stable triphylmethyl radical, attracted a lot of attention at the time and was nominated for the Nobel Prize.

use

The triphenylmethyl group can be easily introduced into a molecule to protect the amino group of an amino acid by reacting the amino acid with two equivalents of trityl chloride in the presence of triethylamine in aprotic solvents. Amino acid esters can be tritylated on the amino group analogously. The protective group is stable under many chemical reaction conditions, but is cleaved off with acid catalysis under mild reaction conditions, for example with hydrogen chloride or hydrochloric acid , with trifluoroacetic acid at 0 to -10 ° C or with glacial acetic acid in the heat. A hydrogenolytic cleavage of the triphenylmethyl protecting group is also possible.

Hydroxy groups in alcohols can be protected as trityl ethers .

Individual evidence

  1. ^ Ulrich Lüning: Organic reactions , 2nd edition, Elsevier GmbH, Munich, 2007, pp. 19-23, ISBN 978-3-8274-1834-0 .
  2. ↑ Thomas T. Tidwell, The first century of Ketenes (1905-2005): the birth of a family of reactive intermediates, Angewandte Chemie, Int. Edition, Volume 44, 2005, pp. 5778-5785.
  3. ↑ JM McBride, Tetrahedron, Volume 30, 1974, pp. 2009-2022.
  4. ↑ M. Gomberg, Ber. Deutsche Chem. Ges., Volume 33, 1900, pp. 3150-3163, Gomberg, J. Am. Chem. Soc., Vol. 22, 1900, pp. 757-771.
  5. ↑ Hans-Dieter Jakubke, Hans Jeschkeit: Amino acids, peptides, proteins , Verlag Chemie, Weinheim, pp. 130-131, 1982, ISBN 3-527-25892-2 .
  6. ↑ Otto-Albrecht Neumüller (Ed.): Römpps Chemie-Lexikon. Volume 6: T-Z. 8th revised and expanded edition. Franckh'sche Verlagshandlung, Stuttgart 1988, ISBN 3-440-04516-1 , p. 4349.