Chihiro Tsukano 교수

An unconventional approach: The total syntheses of nemorosone (1) and clusianone (2) have been achieved in a direct fashion through the generation and exploitation of nonconventional anions arising from a common intermediate (3, see scheme). The key skeleton-building stages are allylative de-aromatization and iodinative cyclization. These acylphloroglucinol natural products display promising cytotoxic and anti-HIV activity, respectively. Recently, our research group described the total synthesis

The first total synthesis of gymnocin-A (1), a cytotoxic polycyclic ether isolated from a notorious red tide dinoflagellate, Karenia mikimotoi, has been accomplished. The synthesis relies heavily on the Suzuki-Miyaura cross-coupling-based methodology to assemble the tetradecacyclic polyether skeleton. Convergent union of the GHI (5) and KLMN (6) rings, both of which were prepared from a common intermediate 7, and the subsequent ring closure of the J ring delivered the GHIJKLMN ring. The crucial

Quite select: a new strategy was developed for the synthesis of various oxindoles from carbamoyl chlorides. Under the optimum reaction conditions, with Ad(2)PBu as a ligand, tBuCONHOH as an additive, and a CO atmosphere, selective C(sp(3))-H activation proceeded in the presence of a C(sp(2))-H bond. Ad=adamantyl.

A highly convergent total synthesis of gymnocin-A, a cyctotoxic polyether marine natural product, has been achieved. The synthesis features Suzuki-Miyaura coupling of the ABCD and FGHIJKLMN rings, stereoselective introduction of the C17 hydroxyl group, ring-closure of the F ring, and a late-stage incorporation of a 2-methyl-2-butenal side chain.

Twice as nice: Total syntheses of dimeric alkaloids, (−)-complanadines A (1) and B (2), were achieved from (−)-lycodine. The unsymmetrical motif was assembled through direct arylation of the pyridine N-oxide. The absolute configuration and specific rotations of complanadines A and B were identified. Cbz=Benzyloxycarbonyl. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for onli

Abstract Lycodine is a representative Lycopodium alkaloid, which features a bicyclo[3.3.1]nonane core and pyridine and piperidine rings. Stereoselective total synthesis of lycodine was achieved using Diels–Alder and intramolecular Mizoroki–Heck reactions.

Abstract The synthesis of spirooxindoles fused with cyclopropanes from carbamoyl chlorides, via methine C(sp3)–H activation, is reported. The regioselectivity of C–H activation in the presence of competitive C–H bonds at the appropriate position was investigated under the optimized conditions.

Although acetalization is a fundamental transformation in organic synthesis, intermolecular asymmetric acetalization remains an unsolved problem. In this study, a thiourea-ammonium hybrid catalyst was shown to promote the O-alkylation of enols with a racemic γ-chlorobutenolide through dynamic kinetic resolution to give chiral acetals with good enantioselectivity. The catalyst simultaneously activates both the nucleophile and electrophile in a multifunctional manner. This method was applied to th

Assoanine, pratosine, hippadine, and dehydroanhydrolycorine belong to the pyrrolophenanthridine family of alkaloids, which are isolated from plants of the Amaryllidaceae species. Structurally, these alkaloids are characterized by a tetracyclic skeleton that contains a biaryl moiety and an indole core, and compounds belonging to this class have received considerable interest from researchers in a number of fields because of their biological properties and the challenges associated with their synt

Ziemlich selektiv: Eine neue Strategie zur Synthese von Oxindolen aus Carbamoylchloriden wurde entwickelt. Unter den optimierten Reaktionsbedingungen mit Ad2PBu als Ligand, tBuCONHOH als Additiv und einer CO-Atmosphäre gelang die selektive C(sp3)-H-Aktivierung in der Gegenwart einer C(sp2)-H-Bindung. Ad=Adamantyl. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available

The first total synthesis of caprazamycin A (1), a representative liponucleoside antibiotic, is described. Diastereoselective aldol reactions of aldehydes 12 and 25-27, derived from uridine, with diethyl isocyanomalonate 13 and phenylcarbamate 21 were investigated using thiourea catalysts 14 or bases to synthesize syn-β-hydroxyamino acid derivatives. The 1,4-diazepanone core of 1 was constructed using a Mitsunobu reaction, and the fatty acid side chain was introduced using a stepwise sequence ba

Unkonventionelles Vorgehen: Die direkten Totalsynthesen von Nemoroson (1) and Clusianon (2) gelangen durch die Erzeugung und Umwandlung ungewöhnlicher Anionen ausgehend von der gemeinsamen Zwischenstufe 3 (siehe Schema). Als Schlüsselschritte beim Gerüstaufbau wurden eine allylierende Desaromatisierung und eine iodierende Cyclisierung genutzt. Die Acylphloroglucin-Naturstoffe zeigen vielversprechende Zytotoxizität bzw. Anti-HIV-Aktivität.

The scope and limitations of the platinum catalyzed 7-endo cyclization of internal alkynyl amides were investigated. Substitution of the alkyne with an aryl group gave better results, presumably because it stabilized the transition state. Applying the reaction to a secondary amide, the caprazamycin core was successfully synthesized from commercially available material in eight steps.

Doppelte Freude: Totalsynthesen der dimeren Alkaloide (−)-Complanadin A (1) und B (2) gelangen ausgehend von (−)-Lycodin. Die unsymmetrische Struktur wurde durch direkte Arylierung eines Pyridin-N-oxids aufgebaut. Die absoluten Konfigurationen und spezifischen Drehwerte der Complanadine wurden ermittelt. Cbz=Benzyloxycarbonyl. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for