CBS catalyst

CBS catalysts or Corey - Bakshi -Shibata catalysts are chiral catalysts and derivatives of the natural amino acid proline. It was named after the chemists EJ Corey, S. Shibata and RK Bakshi, who developed it. CBS catalysts are chiral molecules that cause certain chemical reactions to proceed enantioselectively. This is achieved in that is preferably formed in the transition state one of the two possible enantiomers due to lower steric strain.

CBS catalysts are used in the CBS reduction, the Diels -Alder reaction and the [3 2 ] cycloaddition as a chiral auxiliary.

Chemical structure

CBS reagent is an Boronsäureesteramid a proline derivative, from which the chiral information. The two phenyl moieties in the side chain of the asymmetrically substituted carbon atom, the structure is stiffened and causes a reduction of the rotational degrees of freedom.

Representation

The presentation of the enantiomerically pure amino acid proline or a proline derivative. First, the amino group of proline is provided with a benzyloxycarbonyl protecting group (Cbz -, Z - protecting group ). Then the carboxylic acid is converted to the methyl ester. A Grignard reaction with phenylmagnesium chloride then leads to the tertiary alcohol. Cleavage of the protecting group and subsequent reaction with methyl boronic acid eventually leads to CBS reagent.

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