53007-06-0Relevant articles and documents
Synthesis and stereochemistry of new N-substituted cytisine derivatives
Khakimova,Pukhlyakova,Shavaleeva,Fatykhov,Vasil'eva,Spirikhin
, p. 356 - 360 (2001)
A series of new N-substituted cytisine derivatives was synthesized. The 1H and 13C NMR spectra of certain compounds exhibit a doubled set of signals. This is explained by formation of diastereomeric pairs in compounds containing an asymmetric center in the substituents. The signal splitting in -COHC=CHCO2H and HC=O (formyl) derivatives is explained by the existence of Z and E invertomers. Their stereochemical features are discussed. Amide conjugation is confirmed by temperature experiments.
The Enantioselective Total Synthesis of Bisquinolizidine Alkaloids: A Modular “Inside-Out” Approach
Scharnagel, Dagmar,Goller, Jessica,Deibl, Nicklas,Milius, Wolfgang,Breuning, Matthias
supporting information, p. 2432 - 2435 (2018/02/16)
Bisquinolizidine alkaloids are characterized by a chiral bispidine core (3,7-diazabicyclo[3.3.1]nonane) to which combinations of an α,N-fused 2-pyridone, an endo- or exo-α,N-annulated piperidin(on)e, and an exo-allyl substituent are attached. We developed a modular “inside-out” approach that permits access to most members of this class. Its applicability was proven in the asymmetric synthesis of 21 natural bisquinolizidine alkaloids, among them more than ten first enantioselective total syntheses. Key steps are the first successful preparation of both enantiomers of C2-symmetric 2,6-dioxobispidine by desymmetrization of a 2,4,6,8-tetraoxo precursor, the construction of the α,N-fused 2-pyridone by using an enamine-bromoacrylic acid strategy, and the installation of endo- or, optionally, exo-annulated piperidin(on)es.
Novel Asymmetric Formylation of Aromatic Compounds: Enantioselective Synthesis of Formyl 7,8-Dipropyltetrathia[7]helicenes
Doulcet, Julien,Stephenson, G. Richard
supporting information, p. 13431 - 13436 (2015/09/15)
Asymmetric formylation of aromatic compounds is virtually unexplored. We report the synthesis and evaluation of a library including 20 new chiral formamides in the kinetic resolution of 7,8-dipropyltetrathia[7]helicene, affording the corresponding formyl- or diformylhelicenes in up to 73% ee, making enantiopure compounds available by recrystallisation. With the N,N-disubstituted formamides used in this study, the best enantioselectivity has been achieved with R1=iPr, R2=Me, R3=H, R4=1-naphthyl or its 1-pyrenyl equivalent. Why have chiral formamides been overlooked for so long as tools in asymmetric synthesis? Herein new and efficient procedures are described in which enantioselective delivery of the formyl group achieves kinetic resolution and double kinetic resolution of helicenes, a class of chiral fused aromatic structures that are notoriously difficult to prepare in enantiopure form.
