A reliable, catalytic asymmetric vinylogous Mukaiyama-Mannich reaction of pyrrole-based silyl dienolates is introduced that is particularly apt for alkyl- and α-alkoxyalkyl-substituted aldehydes. The reaction course is effectively orchestrated by the Hoveyda-Snapper amino acid-based chiral ligand/silver(I) catalyst combination to produce valuable vicinal diamino carbonyl compounds in high yields, with virtually complete γ-site- and anti-selectivity and significant catalyst-to-product chirality transfer. The utility of the Mannich products can be seen in the synthesis of an unprecedented perhydrofuro[3,2-b]pyrrolone product, an aza-analogue of naturally occurring (+)-goniofufurone.
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http://dx.doi.org/10.1021/jo201875a | DOI Listing |
J Org Chem
September 2021
Institut für Organische Chemie, Universität Leipzig, Johannisallee 29, D-04103 Leipzig, Germany.
The first enantioselective synthesis of two C-5 diastereomers of the proposed structure of the decahydroquinoline alkaloid - has been achieved. The key step of our strategy is the highly stereoselective vinylogous Mukaiyama-Mannich reaction (VMMR), which gave rise to the first two stereogenic centers at the ring fusion with excellent diastereo- and enantiocontrol. Through alkyne cyclization and enamine reduction the correct -configuration between C-2, C-4a, and C-8a in the decahydroquinoline backbone was established.
View Article and Find Full Text PDFJ Org Chem
October 2020
Institut für Organische Chemie, Universität Leipzig, Johannisallee 29, D-04103 Leipzig, Germany.
The alkaloid (-)-205B has in the past served as a testing ground for novel approaches in nitrogen heterocycle synthesis. We herein report a highly straightforward synthesis of (-)-205B in just six synthetic steps, making it the shortest route currently known. The central steps of our approach are a vinylogous Mukaiyama-Mannich reaction to establish the first two stereogenic centers with excellent diastereo- and enantiocontrol followed by zinc-mediated Barbier allylation to set the third chiral center with high substrate control.
View Article and Find Full Text PDFJ Org Chem
February 2018
Institute of Organic Chemistry, University of Leipzig, Johannisallee 29, D-04103 Leipzig, Germany.
A straightforward synthesis of [1,2-a][3',2'-c]dipyrroloquinolines has been developed generating up to eight new σ-bonds and five new stereogenic centers in a simple and modular one-pot operation. Generally good to excellent yields and moderate to good stereoselectivities in favor of the all-cis stereoisomer were observed. A detailed investigation combining synthetic studies, analytical measurements, and theoretical calculations has been conducted to elucidate the reaction mechanism using ESI- and liquid-beam IR-laser desorption mass spectrometry as well as DFT calculations.
View Article and Find Full Text PDFJ Org Chem
March 2017
Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States.
A class of monomeric nuphar analogues that are either epimeric at C1 and C1' or lack the naturally occurring methyl group at those positions were synthesized and evaluated for biological activity. The syntheses feature enantioselective vinylogous Mukaiyama-Mannich (vM-Mannich) reactions catalyzed by chiral phosphoric acids that proceed with excellent diastereoselectivity. Biological assays reveal that both the desmethyl and C1-epimeric monomeric nuphar analogous are able to induce rapid apoptosis.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
March 2016
Department of Chemistry, Dartmouth College, Hanover, NH, 03755, USA.
Concise, scalable, and enantioselective formal syntheses of eight dimeric and three monomeric nuphar alkaloids were achieved, along with the construction of a stereochemically diverse collection of the first known monomeric analogues having apoptotic activity. The syntheses involved the development of highly enantioselective Brønsted acid catalyzed vinylogous Mukaiyama-Mannich reactions, which feature the unprecedented use of a supersilyl group to control the regio-, enantio- and diastereoselectivity. Biological studies reveal that several of these novel nuphar analogues are even more potent than their dimeric natural product counterparts.
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