Hiroaki Chiba

Construction of Nitrogen Heterocycles Bearing an Aminomethyl Group by Copper-Catalyzed Domino Three-Component Coupling−Cyclization

A direct approach to 2-(aminomethyl)indoles by copper-catalyzed domino three-component coupling-cyclization of 2-ethynylanilines with a secondary amine and aldehyde has been developed. By use of a cyclic or acyclic secondary amine and aldehyde (paraformaldehyde, aliphatic or aromatic aldehydes) in the presence of 1 mol % of CuBr, 2-ethynylanilines were converted to a variety of substituted 2-(aminomethyl)indoles in good to excellent yields. Utilizing this domino reaction and C-H functionalization at the indole C-3 position, polycyclic indoles were readily synthesized. Construction of benzo[e][1,2]thiazine and indene motifs by the reaction of sulfonamide and malonate congeners is also presented.

Concise Synthesis of Indole-Fused 1,4-Diazepines through Copper(I)-Catalyzed Domino Three-Component Coupling-Cyclization-N-Arylation under Microwave Irradiation

Indole-fused benzo-1,4-diazepines were synthesized by copper-catalyzed domino three-component coupling-indole formation- N-arylation under microwave irradiation from a simple N-mesyl-2-ethynylaniline. This method was also applicable to the formation of heterocycle-fused 1,4-diazepines.

Rapid Access to 3-(Aminomethyl)isoquinoline-Fused Polycyclic Compounds by Copper-Catalyzed Four Component Coupling, Cascade Cyclization, and Oxidation

A novel copper-catalyzed synthesis of 3-(aminomethyl)isoquinoline-fused polycyclic compounds, through four-component coupling, cyclization, and oxidation, has been developed. A Mannich-type reaction of 2-ethynylbenzaldehyde with paraformaldehyde and a secondary amine followed by treatment with a diamine component gave tricyclic isoquinolines through cascade cyclization and oxidation. Construction of fused isoquinolines of various ring sizes is also presented.

Total Synthesis of (−)‐Quinocarcin by Gold(I)‐Catalyzed Regioselective Hydroamination

In control: The novel and enantioselective total synthesis of (-)-quinocarcin includes the highly stereoselective preparation of the 2,5-cis-pyrrolidine by intramolecular amination, a selective substrate-controlled 6-endo-dig intramolecular alkyne hydroamination with a cationic Au(I) catalyst, and Lewis-acid-mediated ring-opening/halogenation sequence.

A Simulation Study on the Activation of Cardiac CaMKII δ-Isoform and Its Regulation by Phosphatases

Although the highly conserved Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is known to play an essential role in cardiac myocytes, its involvement in the frequency-dependent acceleration of relaxation is still controversial. To investigate the functional significance of CaMKII autophosphorylation and its regulation by protein phosphatases (PPs) in heart, we developed a new mathematical model for the CaMKIIdelta isoform. Due to better availability of experimental data, the model was first adjusted to the kinetics of the neuronal CaMKIIalpha isoform and then converted to a CaMKIIdelta model by fitting to kinetic data of the delta isoform. Both models satisfactorily reproduced experimental data of the CaMKII-calmodulin interaction, the autophosphorylation rate, and the frequency dependence of activation. The level of autophosphorylated CaMKII cumulatively increased upon starting the Ca(2+) stimulation at 3 Hz in the delta model. Variations in PP concentration remarkably affected the frequency-dependent activation of CaMKIIdelta, suggesting that cellular PP activity plays a key role in adjusting CaMKII activation in heart. The inhibitory effect of PP was stronger for CaMKIIalpha compared to CaMKIIdelta. Simulation results revealed a potential involvement of CaMKIIdelta autophosphorylation in the frequency-dependent acceleration of relaxation at physiological heart rates and PP concentrations.

Formal Total Synthesis of (±)-Strictamine Based on a Gold-Catalyzed Cyclization

A gold-catalyzed cyclization of 1-propargyl-1,2,3,4-tetrahydro-β-carboline led to formation the D-ring of strictamine. Functional group modifications of the resulting tetracyclic indolenine led to the formal total synthesis of (±)-strictamine.

Convergent Synthesis of (−)‐Quinocarcin Based on the Combination of Sonogashira Coupling and Gold(I)‐Catalyzed 6‐endo‐dig Hydroamination

The total synthesis of the pentacyclic tetrahydroisoquinoline alkaloid quinocarcin, which possesses intriguing structural and biological features, has been achieved through a gold(I)-catalyzed regioselective hydroamination reaction. It is noteworthy that the regioselectivity of the intramolecular hydroamination of an unsymmetrical alkyne could be completely switched through substrate control. Other key features of this synthesis include the highly stereoselective synthesis of 2,5-cis-pyrrolidine through the intramolecular amination of the bromoallene and the Lewis acid mediated ring opening of dihydrobenzofuran.

Novel 3,4,7-Substituted Benzofuran Derivatives Having Binding Affinity to κ-Opioid Receptor

A series of novel 3,4,7-trisubstituted benzofuran derivatives were synthesized, and their binding affinity to κ- (KOR) and μ-opioid receptors (MOR) were evaluated. Several aryl ethers showed moderate binding activities to KOR (IC50=3.9-11 µM) without binding to MOR.