7. One-Pot, Three-Component Synthesis of Chiral 4-Alkylidene-2-oxazolidinones
Naoto Kojima, Shogo Nishijima, and Tetsuaki Tanaka, Synlett, 3171-3174 (2009).
Abstract:A one-pot convenient access to chiral 2-oxazolidinones is described.
Diethylzinc-mediated asymmetric alkynylation of aldehydes with
propiolates in the presence of β-sulfonamide alcohol as the chiral
ligand, followed by treatment with isocyanates, yielded chiral
6. Studies of the Asymmetric Total Synthesis of Clavilactone D via 'Lariat' Cyclization Strategy
Takehiko Yoshimitsu, Shoji Nojima, Masashi Hashimoto, Koji Tsukamoto and Tetsuaki Tanaka Synthesis(a Special Issue on "Natural Products Synthesis"）, 2963-2969 (2009).
Abstract:A route to the core structure of clavilactone D, a new member of tyrosine kinase inhibitors, is reported. The present route employs sequential cyclization initiated by iodo etherification followed by Friedel-Crafts cyclization to furnish a polycyclic lactone fused with an aromatic ring, which is readily transformed into the proposed clavilactone scaffold.
5. Medicinal Chemistry of Annonaceous Acetogenins: Design, Synthesis, and Biological Evaluation of Novel Analogues
Naoto Kojima and Tetsuaki Tanaka Molecules (review), 14, 3621-3661 (2009).
Abstract:Most Annonaceous acetogenins are characterized by between one
and three THF ring(s) with one or two flanking hydroxyl group(s) in the
center of a C32/34 fatty acid, and the terminal carboxylic acid is
combined with a 2-propanol unit to form an α, β-unsaturated γ-lactone.
While many studies have addressed the properties and synthesis of
natural acetogenins due to their attractive biological activities and
unique structural features, a number of analogues have also been
described. This review covers the design, synthesis, and biological
evaluation of acetogenin analogues.
4. Total Synthesis of the β-Catenin Inhibitor, (-)-Agelastatin A: A Second-Generation Approach Based on Radical Aminobromination
Takehiko Yoshimitsu, Tatsunori Ino, Naoyuki Futamura, Takuma Kamon and Tetsuaki Tanaka Org. Lett, 11, 3402-3405 (2009).
Abstract:The second-generation approach to (-)-agelastatin A has been established. The present strategy features the FeBr2-mediated radical cyclization of 2-cyclopentenyloxycarbonyl azide that allows for the stereoselective installation of a cis-vicinal aminobromo functionality suitable for producing the BCD-ring system of agelastatin A. The aminobromination method streamlines access to oxazolidinone, a key intermediate in the previously reported synthesis, thereby culminating in the new total synthesis of (-)-agelastatin A.
3. Convergent Synthesis of Fluorescence Labeled Solamin
Naoto Kojima, Takekuni Morioka, Masahiro Yano, Yuki Suga, Naoyoshi Maezaki, and Tetsuaki Tanaka Heterocycles, 79(1), 387-393 (2009).
Abstract:The convergent synthesis of dansyl-labeled solamin, an antitumor
Annonaceous acetogenin, has been achieved. The carbon skeleton was
assembled from three fragments: the THF ring fragment, the fluorescent
fragment, and the γ-lactone fragment, by asymmetric alkynylation.
2. Enantiocontrolled synthesis of polychlorinated hydrocarbon motifs: a nucleophilic multiple chlorination process revisited
Takehiko Yoshimitsu, Naoya Fukumoto, Tetsuaki Tanaka J. Org. Chem., 74(1), 696-702 (2009).
Abstract:Polychlorinated hydrocarbon motifs have been synthesized
in enantiomerically pure forms by means of nucleophilic multiple chlorinations
of chiral epoxides, which stereospecifically incorporate halogen atoms into oxygenated
molecular scaffolds. The present study demonstrates the scope of the N-chlorosuccinimide
(NCS)/organophosphine reagent system that forms multiple sp3C-Cl bonds in a regularly
repeating pattern with proper stereochemical configurations, and evaluates its applicability
to various epoxides having elaborate structures. It is noteworthy that tetrachlorinated motifs
are produced in one step from bisepoxides by using NCS/Ph3P. Furthermore, Ph2PCl used in
combination with NCS has been found to serve as a potentially useful alternate to NCS/Ph3P
especially for promoting dichlorination reactions of alkenyl-substituted epoxides.
1. Synthesis of Chaetomellic Anhydride A, a Potent Inhibitor of Ras Protein Farnesyltransferase
Takehiko Yoshimitsu, Yoshimasa Arano, Tomohiro Kaji, Tatsunori Ino, Hiroto Nagaoka, and Tetsuaki Tanaka Heterocycles, 77(1), 179-186 (2009).
Abstract: Chaetomellic anhydride A, a potent inhibitor of Ras protein farnesyltransferase, was synthesized in 61% yield over four steps from methyl propionate. The synthesis features palladium-catalyzed carboxylation reaction under Cacchi conditions, efficiently incorporating carbon monoxide generated in situ from acetic formic anhydride into β-carbomethoxyalkenyl triflate, and giving rise to the maleic anhydride motif of chaetomellic anhydride A. Noteworthy is the remarkable reactivity of the carboxylation reaction that takes place at room temperature despite the fact that common palladium-catalyzed carboxylations generally require rather harsh conditions. The scope of the method is also presented.