Thiolactones

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Two examples of thiolactones, tetrahydrothiopyran-2-one ( IUPAC thian-2-one , outdated δ-thiovalerolactone , left) and tetrahydrothiophen-2-one (IUPAC thiolan-2-one , outdated γ-thiobutyrolactone , right)
Different types of thiolactones arranged according to increasing ring size, from left to right: α-, β-, γ- and δ-types

As thiolactones refers to a group of sulfur- containing heterocyclic compounds in organic chemistry . In the case of the thiolactones, a sulfur atom is built into a ring system that also has a carbonyl group on the adjacent carbon atom .

The thiol ester bond in the ring system is made between a mercapto - ( Thiohydroxy- ) and a carboxy group composed of the same molecule with elimination of a water molecule. Thiolactones are to be understood as internal (cyclic) thiol esters of mercapto-substituted carboxylic acids . The thiolactones are thus similar to the lactones , the inner esters of hydroxy- substituted carboxylic acids .

Occurrence, appearance and properties

While α- thiolactones are only known as unstable intermediates and the β-thiolactones (four rings) can only be prepared under special conditions, the γ- and δ-thiolactones (five and six rings) are easy to prepare and are stable heterocyclic compounds. γ-lactones can be obtained by evaporating dilute aqueous solutions of the corresponding chain-like γ-mercaptocarboxylic acids. A well-known chiral thiolactone is homocysteine thiolactone (IUPAC: 3-aminothiolan-2-one ). The methyl group of the methionine is split off by heating methionine with aqueous hydriodic acid . During evaporation with elimination of water, the hydroiodide of homocysteine ​​thiolactone is formed as a cyclization product.

(±) -3-Aminothiolan-2-one is formed from (±) -homocysteine ​​when heated with elimination of water.

Various thiolactones are also formed when mixtures of cystine and cysteine are heated . Homocysteine ​​thiolactones trigger programmed cell death in cell cultures and cause chromosomal damage.

See also

Individual evidence

  1. ↑ HS Baernstein, Journal of Biological Chemistry 106 (1934) 451.
  2. ↑ A. Täufel, W. Ternes, L. Tunger, M. Zobel: Lebensmittel-Lexikon. S. 1885, 2005, Behr's Verlag, ISBN 3-89947-165-2 .