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Enantioselective synthesis, also called asymmetric synthesis, [1] is a form of chemical synthesis.It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which one or more new elements of chirality are formed in a substrate molecule and which produces the stereoisomeric (enantiomeric or diastereomeric) products in unequal amounts."
An enantioselective reaction is one in which one enantiomer is formed in preference to the other, in a reaction that creates an optically active product from an achiral starting material, using either a chiral catalyst, an enzyme or a chiral reagent.
While enantioselective epoxidations have been successfully achieved utilizing Sharpless epoxidation, Shi epoxidation, and Jacobsen epoxidation, none of these methods allows for the efficient asymmetric synthesis of terminal epoxides, which are key chiral building blocks. Due to the inexpensiveness of most racemic terminal epoxides and their ...
Josiphos ligands also serve in non-enantioselective reactions: a Pd-catalyzed reaction of aryl chlorides and aryl vinyl tosylates with TON of 20,000 or higher, [8] catalytic carbonylation, [9] or Grignard and Negishi couplings [10] [11] A variety of Josiphos ligands are commercially available under licence from Solvias.
Chiral auxiliaries are incorporated into synthetic routes to control the absolute configuration of stereogenic centers. David A. Evans' synthesis of the macrolide cytovaricin, considered a classic, utilizes oxazolidinone chiral auxiliaries for one asymmetric alkylation reaction and four asymmetric aldol reactions, setting the absolute stereochemistry of nine stereocenters.
The Sharpless epoxidation is viable with a large range of primary and secondary alkenic alcohols. Furthermore, with the exception noted above, a given dialkyl tartrate will preferentially add to the same face independent of the substitution on the alkene.To demonstrate the synthetic utility of the Sharpless epoxidation, the Sharpless group created synthetic intermediates of various natural ...
tert-Butanesulfinamide (also known as 2-methyl-2-propanesulfinamide or Ellman's sulfinamide) is an organosulfur compound and a member of the class of sulfinamides.Both enantiomeric forms are commercially available and are used in asymmetric synthesis as chiral auxiliaries, often as chiral ammonia equivalents for the synthesis of amines.
Enantioselective carbonyl allylations are frequently applied to the synthesis of polyketide natural products. [3] In 1978, Hoffmann reported the first asymmetric carbonyl allylation using a chiral allylmetal reagent, an allylborane derived from camphor.