5. Stereoconvergent route to chiral cyclohexenone building blocks: formal synthesis of (−)-dysidiolide
Gamal A. I. Moustafa , Yasumasa Kamada , Tetsuaki Tanaka and Takehiko Yoshimitsu, Org. Biomol. Chem., 10, 8609-8615 (2012).
Abstract: A stereoconvergent access to chiral carbocyclic building blocks is reported. 6-(3′-Hydroxy-4′-methylpent-4′-enyl)-3-methoxy cyclohex-2-enone (1) that consists of four stereoisomers, i.e., racemic ca. 1:1 diastereomers, is converted to enantiomerically pure carbocycles through a combination of regioselective catalytic asymmetric reduction and alkylative remote stereoinduction. The present stereoconvergent strategy has allowed the formal synthesis of bioactive (−)-dysidiolide.
4.Double CH Functionalization in Sequential Order: Direct Synthesis of Polycyclic Compounds by a Palladium-Catalyzed CH Alkenylation–Arylation Cascade
Hiroaki Ohno, Mutsumi Iuchi, Naoto Kojima, Takehiko Yoshimitsu, Nobutaka Fujii, Tetsuaki Tanaka, Chem. Euro. J. 18, 5352-5360 (2012).
Abstract: Palladium-catalyzed cascade CH alkenylation and arylation provides convenient access to polycyclic aromatic compounds. Treatment of 3-bromoaniline derivatives bearing a bromocinnamyl group on the nitrogen atom with a catalytic amount of [Pd(OAc)2] and PCy3⋅HBF4 in the presence of Cs2CO3 in dioxane affords naphthalene-fused indole derivatives in good yields. This double cyclization reaction is also applicable to heterocyclic substrates, giving fused indoles containing a heteroaromatic ring such as dibenzofuran, dibenzothiophene, carbazole, indole, or benzofuran through heterocyclic CH arylation. When using a 2,6-unsubstituted aniline derivative, the first CH arylation preferentially proceeds at the more hindered position of the aniline ring.
3.Intramolecular iron(II)-catalyzed aminobromination of allyl N-tosyloxycarbamates
Takuma Kamon, Daisuke Shigeoka, Tetsuaki Tanaka and Takehiko Yoshimitsu, Org. Biomol. Chem. 10, 2363-2365 (2012).
Abstract: Allyl N-tosyloxycarbamates are found to be catalytically transformed into β-brominated oxazolidinones with FeBr2/n- Bu4NBr in t-BuOH.
2.Stereoselective α-quaternization of 3-methoxycycloalk-2-enones via 1,4-diastereoinduction of alkoxy dienolates
Gamal A. I. Moustafa, Yasumasa Kamada, Tetsuaki Tanaka, and Takehiko Yoshimitsu, J. Org. Chem. 77, 1202-1207 (2011).
Abstract: The alkylation of dienolates generated from 3-methoxy cycloalk-2-enones having a 3’-hydroxyl alkenyl chain provides the corresponding quaternized cycloalkenones in a highly diastereoselective manner. The high degree of stereocontrol in the alpha-quaternization possibly implies intervention of a rigid chelating transition state that allows an efficient 1,4-asymmetric induction to take place.
1.Pharmacokinetics of Agelastatin A in the central nervous system
Zhimin Li, Takuma Kamon, David A. Personett, Thomas Caulfield, John A. Copland, Takehiko Yoshimitsu and Han W. Tun, Med. Chem. Commun. 3, 233-237 (2012).
Abstract: Agelastatin A (AA) is an anti-neoplastic agent with anti-osteopontin (OPN) activity. Brain tumors often express OPN significantly. A comprehensive chemoinformatic analysis followed by in vivo pharmacokinetic evaluations in mice is performed. CNS penetration of AA is about 10%. AA should be further tested for activity against brain tumors.