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K. Barry Sharpless was the first to develop a general, reliable enantioselective alkene dihydroxylation, referred to as the Sharpless asymmetric dihydroxylation (SAD). Low levels of OsO 4 are combined with a stoichiometric ferricyanide oxidant in the presence of chiral nitrogenous ligands to create an asymmetric environment around the oxidant.
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."
The Sharpless epoxidation is an example of an enantioselective process, in which an achiral allylic alcohol substrate is transformed into an optically active epoxyalcohol. In the case of chiral allylic alcohols, kinetic resolution results. Another example is Sharpless asymmetric dihydroxylation. In the example below the achiral alkene yields ...
The Sharpless asymmetric dihydroxylation [7] was developed by K. Barry Sharpless to use catalytic amounts of OsO 4 along with the stoichiometric oxidant K 3 [Fe(CN) 6]. [1] [2] [8] The reaction is performed in the presence of a chiral auxiliary. The selection of dihydroquinidine (DHQD) or dihydroquinine (DHQ) as a chiral auxiliary dictates the ...
The Sharpless oxyamination (often known as Sharpless aminohydroxylation) is the chemical reaction that converts an alkene to a vicinal amino alcohol. The reaction is related to the Sharpless dihydroxylation , which converts alkenes to vicinal diols. [ 1 ]
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 ...
The Sharpless dihydroxylation is such a reaction: it converts alkenes into diols. The hydroxy groups are provided by hydrogen peroxide , which adds across the double bond of alkenes . [ 12 ]
In 1992, K.B. Sharpless showed that the asymmetric dihydroxylation conditions developed in his group could be harnessed to give either (R)- or (S)- α-hydroxy ketones from the corresponding silyl enol ethers depending on which Chinchona alkaloid-derived chiral ligands were employed. [22]