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Kurihara Y, Yagi M, Noguchi T, Yasufuku H, Okita A, Yoshimura S, Oishi T, Chida N, Okamura T, Sato T. Total Synthesis of Keramaphidin B and Ingenamine by Base-Catalyzed Diels-Alder Reaction Using Dynamic Regioselective Crystallization. J Am Chem Soc 2024. [PMID: 38592076 DOI: 10.1021/jacs.4c02338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/10/2024]
Abstract
The control of the selectivity is a central issue in the total synthesis of complex natural products. In this paper, we report the total synthesis of (±)-keramaphidin B and (±)-ingenamine. The key reaction is a DMAP-catalyzed Diels-Alder reaction in which the regioselectivity is completely controlled by dynamic crystallization. Our synthesis successfully demonstrates that dynamic crystallization can be an alternative when the selectivity is not controlled by either kinetic or thermodynamic approaches in solution.
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Affiliation(s)
- Yuki Kurihara
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Minori Yagi
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Takashi Noguchi
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Haruka Yasufuku
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Ayane Okita
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Sho Yoshimura
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Takeshi Oishi
- School of Medicine, Keio University, 4-1-1, Hiyoshi, Kohoku-ku, Yokohama 223-8521, Japan
| | - Noritaka Chida
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Toshitaka Okamura
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
| | - Takaaki Sato
- Department of Applied Chemistry, Faculty of Science and Technology, Keio University, 3-14-1, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan
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Meng Z, Spohr SM, Tobegen S, Farès C, Fürstner A. A Unified Approach to Polycyclic Alkaloids of the Ingenamine Estate: Total Syntheses of Keramaphidin B, Ingenamine, and Nominal Njaoamine I. J Am Chem Soc 2021; 143:14402-14414. [PMID: 34448391 PMCID: PMC8431342 DOI: 10.1021/jacs.1c07955] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Many
polycyclic marine
alkaloids are thought to derive from partly
reduced macrocyclic alkylpyridine derivatives via a transannular Diels–Alder
reaction that forms their common etheno-bridged diaza-decaline core
(“Baldwin–Whitehead hypothesis”). Rather than
trying to emulate this biosynthesis pathway, a route to these natural
products following purely chemical logic was pursued. Specifically,
a Michael/Michael addition cascade provided rapid access to this conspicuous
tricyclic scaffold and allowed different handles to be introduced
at the bridgehead quarternary center. This flexibility opened opportunities
for the formation of the enveloping medium-sized and macrocyclic rings.
Ring closing alkyne metathesis (RCAM) proved most reliable and became
a recurrent theme en route to keramaphidin B, ingenamine, xestocyclamine
A, and nominal njaoamine I (the structure of which had to be corrected
in the aftermath of the synthesis). Best results were obtained with
molybdenum alkylidyne catalysts endowed with (tripodal) silanolate
ligands, which proved fully operative in the presence of tertiary
amines, quinoline, and other Lewis basic sites. RCAM was successfully
interlinked with macrolactamization, an intricate hydroboration/protonation/alkyl-Suzuki
coupling sequence, or ring closing olefin metathesis (RCM) for the
closure of the second lateral ring; the use of RCM for the formation
of an 11-membered cycle is particularly noteworthy. Equally rare are
RCM reactions that leave a pre-existing triple bond untouched, as
the standard ruthenium catalysts are usually indiscriminative vis-à-vis
the different π-bonds. Of arguably highest significance, however,
is the use of two consecutive or even concurrent RCAM reactions en
route to nominal njaoamine I as the arguably most complex of the chosen
targets.
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Affiliation(s)
- Zhanchao Meng
- Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr, Germany
| | - Simon M Spohr
- Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr, Germany
| | - Sandra Tobegen
- Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr, Germany
| | - Christophe Farès
- Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr, Germany
| | - Alois Fürstner
- Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr, Germany
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Meng Z, Fürstner A. Total Synthesis Provides Strong Evidence: Xestocyclamine A is the Enantiomer of Ingenamine. J Am Chem Soc 2020; 142:11703-11708. [PMID: 32544329 PMCID: PMC7467676 DOI: 10.1021/jacs.0c05347] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
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Xestocyclamine
A ((−)-1) is featured prominently
in a biosynthesis pathway leading to a large family of polycyclic
alkaloids. The first total synthesis now proves that the structure
of this compound had originally been misassigned. The route to (−)-1 is based on a double Michael addition for the formation
of the bridged diazadecalin core and a palladium-catalyzed decarboxylative
allylation to install the quaternary bridgehead center. Ring-closing
alkyne metathesis allowed a 13-membered cycloalkyne to be forged,
which was selectively reduced during an involved sequence of hydroboration/selective
protodeborylation/alkyl-Suzuki coupling used to close the 11-membered
ring. Crystallographic data prove the identity of synthetic (−)-1 with nominal xestocyclamine, but the spectra differ from
those of the authentic alkaloid. To clarify the point, the synthesis
was redirected toward ingenamine (3), which is supposedly
a positional isomer of 1. The recorded data confirm the
assignment of this particular natural product and strongly suggest
that xestocyclamine A is in fact the enantiomer of ingenamine (+)-3.
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Affiliation(s)
- Zhanchao Meng
- Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr, Germany
| | - Alois Fürstner
- Max-Planck-Institut für Kohlenforschung, 45470 Mülheim/Ruhr, Germany
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