Thioester
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robot Adding: [[es:Tioéster]]
[[Image:Thioester-2D-A.png|thumb|right|General structure of a thioester.]]
'''Thioesters''' are compounds resulting from the bonding of [[sulfur]] with an [[acyl]] group with the general formula '''R-S-CO-R''''. They are the product of [[esterification]] between a [[carboxylic acid]] and a [[thiol]] (as opposed to an [[alcohol]] in regular [[ester]]s).
In [[biochemistry]] a thioester connects the acetyl groups in [[acetyl-CoA]] and [[malonyl-CoA]].
==Thioesters and the origin of life==
Some biochemists believe that the thioester bond was critical for the [[origin of life]]. One [[Nobel Prize]] winning scientist, Belgium's [[Christian de Duve]], posits a "Thioester World," which preceded and developed into an "[[RNA World]]," itself the immediate precursor to the appearance of entities we would call [[organism]]s. <ref>de Duve, Christian (Sept./Oct. 1995), ''American Scientist''</ref>
As de Duve explains:
:''A thioester forms when a [[sulfhydryl]] (whose general form is written as an organic group, R, bonded with sulfur and hydrogen, hence R-SH) joins with a [[carboxylic acid]] (R'-COOH). A molecule of [[water]] (H<sub>2</sub>O) is released in the process, and what remains is a thioester: R-S-CO-R'. ...''
:''The thioester bond is what [[biochemistry|biochemists]] call a high-energy bond, equivalent to the phosphate bonds in [[adenosine triphosphate]] ([[adenosine triphosphate|ATP]]), which is the main supplier of energy in all living organisms. ...''
:''It is revealing that thioesters are obligatory intermediates in several key processes in which ATP is either used or regenerated. Thioesters are involved in the synthesis of all [[ester]]s, including those found in complex [[lipid]]s. They also participate in the synthesis of a number of other cellular components, including [[peptide]]s, [[fatty acid]]s, [[sterol]]s, [[terpene]]s, [[porphyrin]]s, and others. In addition, thioesters are formed as key intermediates in several particularly ancient processes that result in the assembly of ATP. In both these instances, the thioester is closer than ATP to the process that uses or yields energy. In other words, thioesters could have actually played the role of ATP in a '''thioester world''' initially devoid of ATP. Eventually, [these] thioesters could have served to usher in ATP through its ability to support the formation of bonds between [[phosphate group]]s.''
==Thionoesters==
[[Image:Methyl-thionobenzoate-2D-skeletal.png|thumb|right|150px|[[Skeletal formula]] of methyl thionobenzoate]]
Thionoesters are isomeric with thioesters. In a thionoester, sulfur replaces the carbonyl oxygen in an [[ester]]. Methyl thionobenzoate is C<sub>6</sub>H<sub>5</sub>C(S)OCH<sub>3</sub>. Such compounds are typically prepared by the reaction of the thioacyl chloride with an alcohol, but they can also be made by the reaction of [[Lawesson's reagent]] with esters.<ref>R. J. Cremlyn “An Introduction to Organosulfur Chemistry” John Wiley and Sons: Chichester (1996). ISBN 0 471 95512 4.</ref>
<center>[[Image:Thionoester-from-thioacyl-chloride-2D-skeletal.png|400 px]]</center>
==References==
{{reflist}}
{{Functional group}}
[[Category:Organosulfur compounds]]
[[Category:Functional groups]]
[[Category:Origin of life]]
[[Category:Thioesters|*]]
[[de:Thioester]]
[[es:Tioéster]]
[[fr:Thioester]]
[[it:Tioestere]]
[[ja:チオエステル]]
[[pl:Tioestry]]
[[tr:Tiyoester]]
[[zh:硫酯]]