7.Design and synthesis of C35-fluorinated solamins and their growth inhibitory activities against human cancer cell lines
Naoto Kojima, Yuki Suga, Hiromi Hayashi, Takao Yamori, Takehiko Yoshimitsu, Tetsuaki Tanaka, Bioorg. Med. Chem. Lett., 21, 5745-5749 (2011).
Abstract: The convergent synthesis of C35-fluorinated analogues of solamin, a mono-THF Annonaceous acetogenin, has been achieved by the Sonogashira coupling of the THF ring fragment and the fluorinated γ-lactone fragment. It was revealed that the number of fluorine atoms on the γ-lactone moiety affects the growth inhibitory activities against human cancer cell lines.
6.Total Synthesis of (±)-Platencin
Takehiko Yoshimitsu, Shoji Nojima, Masashi Hashimoto, and Tetsuaki Tanaka, Org. Lett., 13, 3698-3701 (2011).
Abstract: A novel route to (±)-platencin is reported, in which the highly stereoselective alkylative quaternization of a cyclohexenone scaffold via 1,4-diastereoinduction and two radical carbon–carbon bond-forming reactions that involve titanium(III)-mediated cyclization and stannyl-radical-mediated skeletal rearrangement are utilized.
5. Asymmetric alkynylation of aldehydes with propiolates without high reagent loading and any additives
Naoto Kojima, Shogo Nishijima, Kaoru Tsuge, Tetsuaki Tanaka, Org. Biomol. Chem., 9, 4425-4428 (2011).
Abstract: The asymmetric alkynylation of aliphatic and aromatic aldehydes with propiolates was mediated by dialkylzinc and a novel prolinol catalyst without high reagent loading and any additives, such as Ti(Oi-Pr)4, to give the corresponding γ-hydroxy-α,β-acetylenic esters with high enantiomeric excess of up to 95%.
4. Total Synthesis of (±)-Kainic Acid: A Photochemical C–H Carbamoylation Approach
Takuma Kamon, Yayoi Irifune, Tetsuaki Tanaka, and Takehiko Yoshimitsu, Org. Lett., 13, 2674-2677 (2011).
Abstract: A novel photochemical C–H carbamoylation of an octahydroisoindole derivative with PhNCO has allowed the authors to provide a unique access to a highly functionalized proline motif from which total synthesis of (±)-kainic acid, a bioactive marine alkaloid, has been accomplished.
3.Palladium-catalyzed construction of polycyclic heterocycles by an alkyne insertion and direct arylation cascade
Hiroaki Ohno, Mio Yamamoto, Mutsumi Iuchi, Nobutaka Fujii, Tetsuaki Tanaka, Synthesis, 2567-2578 (2011).
Abstract: Cascade cyclization of bromoenynes bearing an aryl group with catalytic amounts of palladium(II) acetate and cesium carbonate led to the direct construction of tri- or tetracyclic heterocycles. Direct arylation of a pyrrole, furan or thiophene ring in the cascade reaction affords the corresponding fused heteroarenes in moderate to good yields.
2. A novel samarium(II)-mediated tandem spirocyclization onto an aromatic ring
Hiroki Iwasaki, Nozomi Tsutsui, Toru Eguchi, Hiroaki Ohno, Masayuki Yamashita, Tetsuaki Tanaka, Tetrahedron Lett., 52, 1770-1772 (2011).
Abstract: We report a samarium(II)-mediated tandem spirocyclization reaction to provide dispiro[184.108.40.206]tetradecadiene and dispiro[220.127.116.11]pentadecadiene skeletons. The reaction was achieved by intramolecular addition of a ketyl radical onto an aromatic ring bearing an electrophilic moiety followed by reductive capture of the spirohexadienyl radical intermediate with SmI2 in the presence of HMPA.
1. Asymmetric Total Synthesis of (+)-Danicalipin A
Takehiko Yoshimitsu, Ryo Nakatani, Akihiro Kobayashi, Testuaki Tanaka, Org. Lett., 13, 908-911 (2011).
Abstract: A convergent asymmetric total synthesis of (+)-danicalipin A is accomplished, in which two chlorinated fragments are stereoselectively joined by 1,3-dipolar coupling, leading to the confirmation of the absolute configuration of the natural product.