Karl Barry Sharpless developed stereoselective oxidation reactions

Karl Barry Sharpless – developer of stereoselective oxidation reactions

Article on Karl Barry Sharpless

Biography & Contributions

Karl Barry Sharpless is an American chemist and Nobel laureate born on April 28, 1941. Sharpless is regarded as the developer of stereoselective oxidation reactions in the field of click chemistry.

Sharpless received the Scheele Award in the year of 1991, Arthur C. Cope Award in the year of 1992, Tetrahedron Prize in the year of 1993, King Faisal International Prize in the year of 1995, Harvey Prize in the year of 1998, Benjamin Franklin Medal, Wolf Prize and Nobel Prize in Chemistry in the year of 2001.

Sharpless developed stereoselective oxidation reactions, and showed that the formation of an inhibitor with femtomolar potency can be catalyzed by the enzyme acetylcholinesterase, beginning with an azide and an alkyne. He discovered several chemical reactions which have transformed asymmetric synthesis from science fiction to the relatively routine, including aminohydroxylation, dihydroxylation, and the Sharpless asymmetric epoxidation.

He won a half-share of the Nobel Prize in Chemistry for his work on chirally catalyzed oxidation reactions like Sharpless epoxidation, Sharpless asymmetric dihydroxylation, and Sharpless oxyamination.

Sharpless also successfully epoxidized a C-86 Buckminster Fullerene ball, employing p-Cresol as solvent and he was the introducer of new technology in chemistry called click chemistry.

Sharpless Asymmetric Dihydroxylation

Sharpless asymmetric dihydroxylation is the chemical reaction of an alkene with osmium tetroxide in the presence of a chiral quinine ligand to form a vicinal diol. It is common practice to perform this reaction using a catalytic amount of osmium tetroxide, which after reaction is regenerated with either potassium ferricyanide.

Azide-alkyne Huisgen Cycloaddition

Azide-Alkyne Huisgen Cycloaddition is a 1,3-dipolar cycloaddition between an azide and a terminal or internal alkyne to give a 1,2,3-triazole.

Sharpless Epoxidation

Sharpless epoxidation reaction is an enantioselective chemical reaction to prepare 2,3-epoxyalcohols from primary and secondary allylic alcohols. The Sharpless epoxidation's success is due to five major reasons.

First, epoxides can be easily converted into diols, aminoalcohols or ethers, so formation of chiral epoxides is a very important step in the synthesis of natural products. Second, the Sharpless epoxidation reacts with many primary and secondary allylic alcohols.

Third, the products of the Sharpless epoxidation frequently have enantiomeric excesses above 90%. Fourth, the products of the Sharpless epoxidation are predictable using the Sharpless Epoxidation model. Finally, the reactants for the Sharpless epoxidation are commercially available and relatively cheap.

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