Organic reaction methodThe Eschenmoser sulfide contraction is an organic reaction first described by Albert Eschenmoser for the synthesis of 1,3-dicarbonyl compounds from a thioester. The method requires a base and a tertiary phosphine. The method is of some relevance to organic chemistry and has been notably applied in the vitamin B12 total synthesis. 
A base abstracts the labile hydrogen atom in the thioester, a sulfide anion is formed through an episulfide intermediate which is removed by the phosphine. 
Scope.
The Eschenmoser sulfide contraction method has been employed in a number of total synthesis efforts, like that of "fuligocandin A and B", cocaine, "diplodialide A" and "isoretronecanol" 
An example of general synthetic utility is the synthesis of novel carbapenems 
References.
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