Benutzer:Kreuz Elf/Evans–Saksena-Reduktion
The Saksena–Evans reduction is a diastereoselective reduction of β-hydroxy ketones to the corresponding anti-dialcohols, employing the reagent tetramethylammonium triacetoxyborohydride (Me4NHB(OAc)3). The reaction was first described by Anil K. Saksena in 1983[1] and further developed by David A. Evans in 1987.[2]
The reaction is thought to proceed through the 6-membered ring transition state shown below. The intramolecular hydride delivery from the boron reducing agent forces the reduction to proceed from the opposite face of the chelating β-alcohol, thus determining the diastereoselectivity.
This can be contrasted with the Narasaka–Prasad reduction which similarly employs a boron chelating agent but undergoes an intermolecular hydride delivery, favouring the corresponding syn-diol product.
The Saksena-Evans reduction has since been used in the synthesis of several products, particularly the bryostatins.[3][4]
See also
[Bearbeiten | Quelltext bearbeiten]Einzelnachweise
[Bearbeiten | Quelltext bearbeiten]- ↑ Anil Saksena, Pietro Mangiaracina: Recent studies on veratrum alkaloids: a new reaction of sodium triacetoxyborohydride [NaBH(OAc)3]. In: Tetrahedron Letters. 24. Jahrgang, Nr. 3, 1983, S. 273–276, doi:10.1016/S0040-4039(00)81383-0.
- ↑ David Evans, K. Chapman, E. Carreira: Directed reduction of β-hydroxy ketones employing tetramethylammonium triacetoxyborohydride. In: Journal of the American Chemical Society. 110. Jahrgang, Nr. 11, 1988, S. 3560–3578, doi:10.1021/ja00219a035.
- ↑ Satoru Masamune: Asymmetric synthesis and its applications: Towards the synthesis of bryostatin 1. In: Pure Appl. Chem. 60. Jahrgang, Nr. 11, 1988, S. 1587–1596, doi:10.1351/pac198860111587 (iupac.org [PDF; abgerufen am 30. Dezember 2012]).
- ↑ Kyoko Nakagawa-Goto, Michael Crimmins: Synthetic Approaches to the Bottom Half Fragment for Bryostatin 11. In: Synlett. 2011. Jahrgang, Nr. 11, 2011, S. 1555–1558, doi:10.1055/s-0030-1260784.
[[Category:Name reactions]]