Journal ArticleDOI
Stereocontrolled Elaboration of Quaternary Carbon Centers through the Asymmetric Michael-Type Alkylation of Chiral Imines/Secondary Enamines: Enantioselective Synthesis of (+)-Vincamine
TLDR
In this paper, an enantioselective synthesis of (+)-vincamine (1) was developed, where the key strategic element was the stereocontrolled elaboration of a quaternary carbon center (future C-20 center of 1) by using the asymmetric Michael reaction involving chiral imines/secondary enamines under neutral conditions.Abstract:
An enantioselective synthesis of (+)-vincamine (1) has been developed. The key strategic element was the stereocontrolled elaboration of a quaternary carbon center (future C-20 center of 1) by using the asymmetric Michael reaction involving chiral imines/secondary enamines under neutral conditions. Thus, addition of enaminolactam (S)-12, derived from ketolactam 7 (itself prepared in four steps from commercially available tryptamine) and (S)-1-phenylethylamine, to methyl acrylate led, after hydrolytic workup, to adduct (R)-6 with a 90% stereoselectivity. The critical removal of the additional keto group of 6 was then examined. After extensive experimentation, we finally established that the most efficient deoxygenation procedure was the Wolff−Kishner reduction of the corresponding keto acid, which proceeded with a 55% yield. The cornerstone [ABD]-tricyclic lactam ester 38 thus obtained was next cyclized under Bischler−Napieralski reaction conditions to afford, after catalytic hydrogenation of the intermedi...read more
Citations
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Journal ArticleDOI
Enantioselective Construction of Quaternary Stereocenters
Jens Christoffers,Alexander Mann +1 more
TL;DR: In this Minireview examples of newer stoichiometric and catalytic methods are summarized which have proved their suitability for the enantioselective construction of quaternary stereocenters.
Journal ArticleDOI
Enantioselektiver Aufbau quartärer Stereozentren
Jens Christoffers,Alexander Mann +1 more
TL;DR: The stereoselektive Knupfung von C-C-Bindungen is von zentraler Bedeutung fur die Synthese enantiomerenreiner Natur-and Wirkstoffe as discussed by the authors.
Journal ArticleDOI
Enantioselective Organocatalytic Conjugate Addition of Aldehydes to Vinyl Sulfones and Vinyl Phosphonates as Challenging Michael Acceptors
Sarah Sulzer-Mossé,Alexandre Alexakis,Jiri Mareda,Guillaume Bollot,Gérald Bernardinelli,Yaroslav Filinchuk +5 more
TL;DR: This novel process provides synthetically useful chiral gamma-gem-sulfonyl or phosphonyl aldehydes which can be widely functionalized with retention of the enantiomeric excess.
Journal ArticleDOI
Practical procedures for the preparation of N-tert-butyldimethylsilylhydrazones and their use in modified Wolff-Kishner reductions and in the synthesis of vinyl halides and gem-dihalides.
TL;DR: Aliphatic and aromatic ketones and aldehydes are shown to undergo highly efficient coupling to form the corresponding TBSH derivatives when combined with equimolar amounts of 1,2-bis(tert-butyldimethylsilyl)hydrazine (BTBSH) and a catalytic quantity of scandium trifluoromethanesulfonate (typically, 0.01 mol %).
Journal ArticleDOI
Indole Alkaloid Synthesis Facilitated by Photoredox Catalytic Radical Cascade Reactions
Xiao-Yu Liu,Yong Qin +1 more
TL;DR: The visible-light-driven cascade strategy will find further utility in the realm of natural product synthesis, and expansion of this catalytic, scalable, and general methodology permitted the total synthesis of a large collection of indole alkaloids.
References
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Journal ArticleDOI
A uniform numbering system for indole alkaloids.
TL;DR: Nous proposons un mode uniforme de numérotation pour le squelette des alcaloïdes indoliques complexes complexes d'être coupés en éléments identiques.
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The asymmetric Michael addition reactions using chiral imines
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An efficient and practical total synthesis of (+)-vincamine from L-aspartic acid
TL;DR: In this article, the authors presented an optically pure α-tert-butyl β-methyl (2S,3R)-3-ethylhexahydroquinolinate (EHQ) in 54-59% yield from L-aspartic acid was the foundation for a practical synthesis of (+)-vincamine.