Journal ArticleDOI
Asymmetric total synthesis of(–)-protoemetinol,(–)-protoemetine,(–)-emetine, and (–)-tubulosine by highly stereocontrolled radical cyclisations
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TLDR
Both enantiomers of the menthyl halfesters (10) and (23) of ethylmalonic acid were converted into (+)-(4S,5R)-4-(2-benzyloxyethyl)-5-ethyl-3,4,5,6-tetrahydro-2-pyrone (18) as discussed by the authors.Abstract:
Both enantiomers of the menthyl half-esters (10) and (23) of ethylmalonic acid were converted into(+)-(4S,5R)-4-(2-benzyloxyethyl)-5-ethyl-3,4,5,6-tetrahydro-2-pyrone (18). A mixture of the trans-(18) and cis-lactones (19) in a ratio of ca. 4 : 1 was prepared by way of radical cyclisation of the (E)-α,β-unsaturated esters (16), while the former (18) was synthesised with high stereoselection by the cyclisation of the (Z)-esters (26). The lactone (18) was enantioselectively transformed into (–)-protoemetimol (5) and (–)-protoemetine (4), correlated to (–)-emetine (1) and (–)-tubulosine (3).read more
Citations
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Stereochemistry of intramolecular free-radical cyclization reactions
Journal ArticleDOI
Catalytic asymmetric allylation of 3,4-dihydroisoquinolines and its application to the synthesis of isoquinoline alkaloids.
Michiko Miyazaki,Nami Ando,Keita Sugai,Yuki Seito,Hiromi Fukuoka,Takuya Kanemitsu,Kazuhiro Nagata,Yuki Odanaka,Kazuo T. Nakamura,Takashi Itoh +9 more
TL;DR: A catalytic asymmetric allylation of 3,4-dihydroisoquinoline was carried out with allyltrimethoxylsilane-Cu as the nucleophile and the allyl adduct obtained was applied to the synthesis of several isoquinoline alkaloids such as crispine A and homolaudanosine.
Journal ArticleDOI
A stereodivergent strategy for the preparation of corynantheine and ipecac alkaloids, their epimers, and analogues: efficient total synthesis of (-)-dihydrocorynantheol, (-)-corynantheol, (-)-protoemetinol, (-)-corynantheal, (-)-protoemetine, and related natural and nonnatural compounds.
TL;DR: The potential of this strategy is demonstrated in the synthesis of biologically interesting natural product analogues not accessible through synthetic elaboration of alkaloid precursors available from nature, for example, thieno[3,2-a]quinolizidine derivatives.
Journal ArticleDOI
Intramolecular reductive cyclisations using electrochemistry: development of environmentally friendly synthetic methodologies
TL;DR: In this article, a review summarises electrochemical reductive intramolecular cyclisations, including transition-metal catalysed reactions, and presents some selected examples of organic halide electroreductions with further intramerolecular coupling reactions, carbonyl group reductions with further coupling, and intramerial cyclisations involving electrogenerated bases.
References
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Journal ArticleDOI
Total synthesis of (±)-alliacolide
Mark Ladlow,Gerald Pattenden +1 more
TL;DR: A total synthesis of the unique epoxy-lactone alliacolide, featuring a novel, stereoselective intramolecular radical cyclisation onto an enolic double-bond, viz (13) → (14), as a key step, is described in this paper.
Journal ArticleDOI
New alkaloids from alangium lamarckii THW.
Journal ArticleDOI
1,2-Asymmetric induction in intramolecular Michael reaction. A novel and enantioselective route to (+)-Geissman lactone
TL;DR: The Horner-Emmons reaction of the hemiacetal (19), derived from L-(+)-diethyl tartrate, was found to give the pyrrolidine (21) via an intramolecular Michael reaction as a mixture of diastereoisomers which, after treatment with ethanethiol and boron trifluoride-diethy ether, was converted into the lactone (22) and the ester (23) as mentioned in this paper.
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