Jun Shimokawa 교수

The first total synthesis of gelsemoxonine (1) has been accomplished. Divinylcyclopropane-cycloheptadiene rearrangement of the highly functionalized substrate was successfully applied to assemble the spiro-quaternary carbon center connected to the bicyclic seven-membered core structure. A one-pot isomerization reaction of the α,β-unsaturated aldehyde to the saturated ester via the TMSCN-DBU reagent combination allowed a facile diastereoselective introduction of the latent nitrogen functionality

One-step formation of an enone from a primary alcohol has been effectively applied in the total synthesis of batzelladine A (1). Successive 1,3-dipolar cycloadditions with a subsequent cyclization were used to form the tricyclic guanidine subunit of this natural product, which has the strongest inhibitory activity of HIV gp120-CD4 binding among the batzelladines.

Divergent strategy in natural product synthesis allows the comprehensive synthesis of family natural products. Efficient formulation of this idea requires the biosynthetic/biosynthesis-inspired insight toward the well-orchestrated design of a pluripotent late-stage intermediate, in concomitant with the applicability of the intermediates for versatile transformations. This digest focuses on the actual applications of those strategies in natural product synthesis with an emphasis on the recipes fo

Asymmetric total synthesis of batzelladine A (1) and batzelladine D (2) has been achieved. Our synthesis of batzelladines features 1) stereoselective construction of the cyclic guanidine system by means of successive 1,3-dipolar cycloaddition reaction and subsequent cyclization, 2) direct esterification of the bicyclic carboxylic acid 35 with the guanidine alcohol 8 or 59 to construct the whole carbon skeleton of batzelladines, and 3) one-step formation of the alpha,beta-unsaturated aldehyde 53

The multifaceted implementation of silanols in organic synthesis is reviewed from the standpoint of developments in transition metal-catalyzed reactions. The major properties of silanols are summarized according to the research fields that have utilized these intriguing species: silanols as nucleophiles to serve as bulky surrogates for water; silanols as temporary ligands to control regioselectivity of metal-catalyzed reactions; silanols as coupling partners for transferring functional groups. T

There is an increasing demand for facile delivery of silyl groups onto organic bioactive molecules. One of the common methods of silylation via a transition-metal-catalyzed coupling reaction employs hydrosilane, disilane, and silylborane as major silicon sources. However, the labile nature of the reagents or harsh reaction conditions sometimes render them inadequate for the purpose. Thus, a more versatile alternative source of silyl groups has been desired. We hereby report a design, synthesis,

Assisted by the total syntheses of all the amathaspiramides, six natural products and four synthetic intermediates with partially fluctuating structures were prepared and subjected to a growth inhibition assay in four human cancer cell lines. The results showed amathaspiramides A, C, and E had moderate antiproliferative activity. Examination of the structure-activity relationship revealed the importance of the amine or imine substructure on the pyrrolidine moiety and the 8R stereochemistry on th

The core skeleton of phalarine was rapidly synthesised through novel palladium-catalysed dearomative spirocyclisation and a palladium-catalysed Wacker-carbonylative cyclisation cascade. The two key steps allowed for the efficient construction of a tricyclic propeller skeleton bearing contiguous tetrasubstituted carbon centres, within 3 steps from a topologically planar precursor.

Organic synthesis is performed based on precise choices of functional groups and reactions employed. In a multistep synthesis, an ideal functional group should be compatible with various reaction conditions and unaltered until it is subjected to a selective conversion. The current study was set out to search for a silicon functionality that meets these criteria. Here we have established a new silicon-based synthetic methodology centred on a bulky 7-membered dialkoxysilyl group (2,4,4,7,7-pentame

Ein Enon in einem Schritt aus dem primären Alkohol – das war ein wichtiger Beitrag zur Totalsynthese von Batzelladin A (1). Die tricyclische Guanidineinheit von 1 wurde durch aufeinander folgende 1,3-dipolare Cycloadditionen und anschließende Cyclisierung erhalten. 1 ist unter den Batzelladinen der stärkste Inhibitor für die Bindung von HIV gp120-CD4.

The first total synthesis of gelsemoxonine has been accomplished. A divinylcyclopropane–cycloheptadiene rearrangement of the highly functionalized substrate successfully assembled the spiro-quaternary carbon center connected to the bicyclic seven-membered core structure. A one-pot isomerization reaction of the α,β-unsaturated aldehyde to the saturated ester via a trimethylsilyl cyanide–diazabicycloundecene (TMSCN–DBU) reagent combination allowed a facile and diastereoselective introduction of th

Visible light photoredox conditions were applied to the traditional Fischer indole synthesis. N,N-Diarylhydrazones were efficiently converted into the corresponding indoles even at 30 °C by treatment with bromotrichloromethane in the presence of Ru(bpy)3Cl2·6H2O as the photocatalyst. Electrochemical study revealed the viability of oxidative quenching cycle for the photocatalysis, which set the basis for proposing the redox-based reaction mechanism.

We report a copper‐catalyzed amination reaction between simple alkoxyarylsilanes and N ‐benzoyloxyamines. Silver fluoride serves as a stoichiometric base as well as an indispensable activator that allows the catalytic process to proceed. Multiply alkoxylated arylsilanes, such as trialkoxyarylsilanes and dialkoxyarylsilanes were transformed into the corresponding tertiary anilines under mild reaction conditions.

Silylcoppers function as convenient and effective sources of silicon functional groups. Commonly used precursors for those species have been limited to certain symmetric disilanes and silylboranes. This fact renders the development of silylcopper precursors desirable so that more diverse silyl groups could be efficiently delivered. Here we extend the utility of sodium silylsilanolates as competent precursors of silylcoppers. A silanolate unit operates as an auxiliary to transfer a variety of sil