- Unified Total Synthesis of Madangamine Alkaloids
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The full details of a unified total synthesis of madangamine alkaloids are disclosed. Our central strategy is based on the construction of a common ABCE-tetracyclic system, followed by the late-stage installation of various D-rings. The common intermediate is assembled through N-acyliminium cyclization of a propargylsilane, and formation of the (Z,Z)-skipped diene. Stereoselective synthesis of the (Z,Z)-skipped diene is especially challenging, and is accomplished by the combination of Z-selective hydroboration of the 1,1-disubstituted allene and subsequent Migita-Kosugi-Stille coupling. Macrocyclic alkylation enables the late-stage variation of the D-rings on the common tetracyclic intermediate, resulting in the collective total syntheses of madangamines AE. The synthetic madangamine alkaloids exhibited inhibitory activities against a variety of human cancer cell lines.
- Suto, Takahiro,Yanagita, Yuta,Nagashima, Yoshiyuki,Takikawa, Shinsaku,Kurosu, Yasuhiro,Matsuo, Naoya,Miura, Kazuki,Simizu, Siro,Sato, Takaaki,Chida, Noritaka
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- O-Alkyl S-(Pyridin-2-yl)carbonothiolates: Operationally Simple and Highly Nitrogen-Selective Reagents for Alkoxy Carbonylation of Amino Groups
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Amino groups are selectively protected in good yields by reaction with O-Alkyl S-(pyridin-2-yl)carbonothiolates in an appropriate solvent at room temperature in air. Even glucosamine, which contains multiple hydroxyl groups, is selectively N-protected in methanol.
- Hashimoto, Yoshimitsu,Morita, Nobuyoshi,Suzuki, Tomoyuki,Tamura, Osamu,Tanaka, Kosaku
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p. 899 - 902
(2020/05/28)
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- Unified Total Synthesis of Madangamines A, C, and E
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A stereodivergent strategy for the synthesis of skipped dienes is developed. The method consists of hydroboration of allenes and Migita-Kosugi-Stille coupling, which allows for access to all four possible stereoisomers of the skipped dienes. The hydroboration is especially useful for providing both E-allylic and Z-allylic alcohols from the same allene by simply changing the organoborane reagent. The strategy was successfully applied to a unified total synthesis of the madangamine alkaloids via a common ABCE-tetracyclic intermediate with a (Z,Z)-skipped diene. The late-stage variation of the D-ring enabled the supply of synthetic madangamines A, C, and E for the first time.
- Suto, Takahiro,Yanagita, Yuta,Nagashima, Yoshiyuki,Takikawa, Shinsaku,Kurosu, Yasuhiro,Matsuo, Naoya,Sato, Takaaki,Chida, Noritaka
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supporting information
p. 2952 - 2955
(2017/03/11)
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- Benzannulation via the reaction of ynamides and vinylketenes. Application to the synthesis of highly substituted indoles
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A two-stage "tandem strategy" for the synthesis of indoles with a high level of substitution on the six-membered ring is described. Benzannulation based on the reaction of cyclobutenones with ynamides proceeds via a cascade of four pericyclic reactions to produce multiply substituted aniline derivatives in which the position ortho to the nitrogen can bear a wide range of functionalized substituents. In the second stage of the tandem strategy, highly substituted indoles are generated via acid-, base-, and palladium-catalyzed cyclization and annulation processes.
- Lam, Tin Yiu,Wang, Yu-Pu,Danheiser, Rick L.
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p. 9396 - 9414
(2013/10/08)
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- Amino-Protecting Reagents: New Promising Reagents for tert-Butoxycarbonylation, Benzyloxycarbonylation, and carbonylation
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A new method for the preparation of tert-butyl- (1d), benzyl- (1e), and (β-trimethylsilyl)ethyl α-methoxyvinyl carbonates (1f) has been devised.The reaction of these reagents with amino compounds proceeds rapidly under mild conditions to give the corresponding N-tert-butoxycarbonylated (N-Boc), N-benzyloxycarbonylated (N-Z), and N-carbonylated (N-Tmseoc) compounds in quantitative yields.Twenty-two examples using amines, amino alcohols, and amino acids were presented.
- Kita, Yasuyuki,Haruta, Jun-ichi,Yasuda, Hitoshi,Fukunaga, Keiko,Shirouchi, Yoshiaki,Tamura, Yasumitsu
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p. 2697 - 2700
(2007/10/02)
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