- Enantioselective Syntheses of Strychnos and Chelidonium Alkaloids through Regio- and Stereocontrolled Cooperative Catalysis
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We describe enantioselective syntheses of strychnos and chelidonium alkaloids. In the first case, indole acetic acid esters were established as excellent partner nucleophiles for enantioselective cooperative isothiourea/Pd catalyzed α-alkylation. This provides products containing indole-bearing stereocenters in high yield and with excellent levels of enantioinduction in a manner that is notably independent of the N-substituent. This led to concise syntheses of (?)-akuammicine and (?)-strychnine. In the second case, the poor performance of ortho-substituted cinnamyl electrophiles in the enantioselective cooperative isothiourea/Ir catalyzed α-alkylation was overcome by appropriate substituent choice, leading to enantioselective syntheses of (+)-chelidonine, (+)-norchelidonine, and (+)-chelamine.
- Fyfe, James W. B.,Hutchings-Goetz, Luke S.,Snaddon, Thomas N.,Yang, Chao
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p. 17556 - 17564
(2020/08/14)
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- Enantioselective synthesis of chelidonine, a B/C-cis-11- hydroxyhexahydrobenzo[c]phenanthridine alkaloid
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Both enantiomers of chelidonine, a B/C-cis-11-hydroxyhexahydrobenzo[c] phenanthridine alkaloid, were synthesized by manipulation of the B/C-dehydro ring juncture of benzo[c]phenanthridine skeleton using Sharpless asymmetric dihydroxylation and stereospecific catalytic hydrogenation after introduction of oxygen functions on the C ring as key reaction steps for the construction of stereogenic centers.
- Ito, Miki,Konno, Fujiko,Kumamoto, Takuya,Suzuki, Noriyuki,Kawahata, Masatoshi,Yamaguchi, Kentaro,Ishikawa, Tsutomu
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p. 8041 - 8049
(2011/11/12)
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- Concise enantioselective total syntheses of (+)-homochelidonine, (+)-chelamidine, (+)-chelidonine, (+)-chelamine and (+)-norchelidonine by a PdII-catalyzed ring-opening strategy
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New enantioselective syntheses of the B/C hexahydrobenzo[c]phenanthridine alkaloids (+)-homochelidonine, (+)-chelamidine, (+)-chelidonine, (+)-chelamine, and (+)-norchelidonine are described. Our rapid and convergent route to this class of natural products involved the development and application of a Pd II-catalyzed asymmetric ring-opening reaction of a mesoazabicyclic alkene with an aryl boronic acid as the key step. By screening a variety of functionalized ortho-substituted aryl boronic acids, chiral ligands and reaction conditions we were able to prepare the requisite cis-1-amino-2- aryldihydronaphthalenes in high yield and in up to 90% ee. Early attempts to complete the synthesis of (+)-homochelidonine using an N-Boc azabicyclic alkene are described in full. The successful route required a protecting group alteration followed by B ring for-mation and then stereoselective installation of the C-11 syn-hydroxy group by regioselective epoxide ring-opening using a hydride source. Ring-opening of the same epoxide intermediate with water ultimately led to the synthesis of (+)-chelamidine. The same strategy was then used to synthesize the other structurally similar B/C hexahydrobenzo[c] phenanthridine alkaloids, (+)-chelidonine, (+)-chelamidine, and (+)norchelidonine.
- Fleming, Matthew J.,McManus, Helen A.,Rudolph, Alena,Chan, Walter H.,Ruiz, Jeremy,Dockendorff, Chris,Lautens, Mark
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experimental part
p. 2112 - 2124
(2009/04/06)
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