- Stereoselective total synthesis of (±)-homochelidonine
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(±)-Homochelidonine, a B/C-cis-11-hydroxyhexahydrobenzo[c]phenanthridine alkaloid, was stereoselectively synthesized from arnottin II, a non-alkaloidal spirolactonyl tetralone which had been structurally correlated to chelerythrine, a fully aromatized-type alkaloid, by the common use of a 2-benzofuranyl-1-tetralone as a synthetic key intermediate. Thus, a valuable synthetic method accessible to benzo[c]phenanthridine alkaloids with different oxidation stages of the basic skeleton could be proposed.
- Yoshida, Makoto,Watanabe, Toshiko,Ishikawa, Tsutomu
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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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- Enantioselective total synthesis of (+)-homochelidonine by a Pd II-catalyzed asymmetric ring-opening reaction of a meso-azabicyclic alkene with an aryl boronic acid
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(Chemical Equation Presented) An efficient and highly convergent enantioselective synthesis of (+)-homochelidonine has been achieved (see scheme; Cbz = benzyloxycarbonyl, MOM = methoxymethyl) and relied on a new and powerful desymmetrizing ring-opening reaction of a meso-azabicycle with an aryl boronic acid. The route should allow access to other hexahydrobenzo[c]phenanthridine alkaloids.
- McManus, Helen A.,Fleming, Matthew J.,Lautens, Mark
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p. 433 - 436
(2008/02/02)
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- Photocyclisation of Enamides. Part 19. Total Synthesis of (+/-)-Homochelidonine
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Photocyclisation of the enamide (2) and successive stereoselective functionalisation of the photocyclised didehydro lactam (3a) completed the first total synthesis of (+/-)-homochelidonine (7e).
- Ninomiya, Ichiya,Yamamoto, Okiko,Naito, Takeaki
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p. 2171 - 2174
(2007/10/02)
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