Chiral auxiliary

In stereochemistry, a chiral auxiliary is a stereogenic group or unit that is temporarily incorporated into an organic compound in order to control the stereochemical outcome of the synthesis.^[1]^[2] The chirality present in the auxiliary can bias the stereoselectivity of one or more subsequent reactions. The auxiliary can then be typically recovered for future use.

General scheme for employing a chiral auxiliary in asymmetric synthesis

Most biological molecules and pharmaceutical targets exist as one of two possible enantiomers; consequently, chemical syntheses of natural products and pharmaceutical agents are frequently designed to obtain the target in enantiomerically pure form.^[3] Chiral auxiliaries are one of many strategies available to synthetic chemists to selectively produce the desired stereoisomer of a given compound.^[4]

Chiral auxiliaries were introduced by Elias James Corey in 1975^[5] with chiral 8-phenylmenthol and by Barry Trost in 1980 with chiral mandelic acid. The menthol compound is difficult to prepare and as an alternative trans-2-phenyl-1-cyclohexanol was introduced by J. K. Whitesell in 1985.

^ Key Chiral Auxiliary Applications (Second Edition)(ed.: Roos, G.), Academic Press, Boston, 2014 ISBN 978-0-12-417034-6
^ Glorius, F.; Gnas, Y. (2006). "Chiral Auxiliaries — Principles and Recent Applications". Synthesis. 2006 (12): 1899–1930. doi:10.1055/s-2006-942399.
^ Jamali, Fakhreddin (1993). "Chapter 14: Stereochemically Pure Drugs: An Overview". In Wainer, Irving W. (ed.). Drug Stereochemistry: Analytical Methods and Pharmacology. Marcel Dekker, Inc. pp. 375–382. ISBN 978-0-8247-8819-3.
^ Evans, D. A.; Helmchen, G.; Rüping, M. (2007). "Chiral Auxiliaries in Asymmetric Synthesis". In Christmann, M (ed.). Asymmetric Synthesis — The Essentials. Wiley-VCH Verlag GmbH & Co. pp. 3–9. ISBN 978-3-527-31399-0.
^ Cite error: The named reference Corey1975 was invoked but never defined (see the help page).

[1] Key Chiral Auxiliary Applications (Second Edition)(ed.: Roos, G.), Academic Press, Boston, 2014 ISBN 978-0-12-417034-6

[Glorius_review2-2] Glorius, F.; Gnas, Y. (2006). "Chiral Auxiliaries — Principles and Recent Applications". Synthesis. 2006 (12): 1899–1930. doi:10.1055/s-2006-942399.

[3] Jamali, Fakhreddin (1993). "Chapter 14: Stereochemically Pure Drugs: An Overview". In Wainer, Irving W. (ed.). Drug Stereochemistry: Analytical Methods and Pharmacology. Marcel Dekker, Inc. pp. 375–382. ISBN 978-0-8247-8819-3.

[Evans_review-4] Evans, D. A.; Helmchen, G.; Rüping, M. (2007). "Chiral Auxiliaries in Asymmetric Synthesis". In Christmann, M (ed.). Asymmetric Synthesis — The Essentials. Wiley-VCH Verlag GmbH & Co. pp. 3–9. ISBN 978-3-527-31399-0.

[Corey1975-5] Cite error: The named reference Corey1975 was invoked but never defined (see the help page).

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Chiral auxiliary

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