title: A Catalyst Designed for the Enantioselective Construction of Methyl- and Alkyl-Substituted Tertiary Stereocenters.
abstract: Tertiary methyl-substituted stereocenters are present in numerous biologically active natural products. Reported herein is a catalytic enantioselective method for accessing these chiral building blocks using the Mukaiyama-Michael reaction between silyl ketene thioacetals and acrolein. To enable remote enantioface control on the nucleophile, a new iminium catalyst, optimized by three-parameter tuning and by identifying substituent effects on enantioselectivity, was designed. The catalytic process allows rapid access to chiral thioesters, amides, aldehydes, and ketones bearing an α-methyl stereocenter with excellent enantioselectivities, and allowed rapid access to the C4-C13 segment of (-)-bistramide A. DFT calculations rationalized the observed sense and level of enantioselectivity.
authors.affiliation: Department of Chemistry, Nanoscience Center, University of Jyväskylä, P. O. B. 35, 40014 JYU (Finland) http://tinyurl.com/pihkogroup.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Claraz
authors.affiliation: Department of Chemistry, Nanoscience Center, University of Jyväskylä, P. O. B. 35, 40014 JYU (Finland) http://tinyurl.com/pihkogroup.
authors.forename: Gokarneswar
authors.initials: G
authors.lastname: Sahoo
authors.affiliation: Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1525 Budapest (Hungary).
authors.forename: Dénes
authors.initials: D
authors.lastname: Berta
authors.affiliation: Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1525 Budapest (Hungary).
authors.forename: Ádám
authors.initials: Á
authors.lastname: Madarász
authors.affiliation: Institute of Organic Chemistry, Research Centre for Natural Sciences, Hungarian Academy of Sciences, 1525 Budapest (Hungary).
authors.forename: Imre
authors.initials: I
authors.lastname: Pápai
authors.affiliation: Department of Chemistry, Nanoscience Center, University of Jyväskylä, P. O. B. 35, 40014 JYU (Finland) http://tinyurl.com/pihkogroup. petri.pihko@jyu.fi.
authors.forename: Petri M
authors.initials: PM
authors.lastname: Pihko
keywords: asymmetric catalysis; density functional calculations; diastereoselectivity; natural products; organocatalysis