Publications by authors named "Chun-Young Lee"

Asymmetric total syntheses of naphthylisoquinoline alkaloids with a ()-configuration are described. An atroposelective Suzuki-Miyaura reaction between naphthyl pinacol boronate and an aryl iodide bearing an ()-2-(-acetylamino)propyl group at the -position using Pd(OAc) in the presence of SPhos and Ba(OH) provided the ()-selective biaryl product as the major product without any external chiral sources. This biaryl product was converted into naphthylisoquinoline alkaloids with a ()-configuration via stereoselective construction of the isoquinoline framework with the appropriate oxidation state and stereochemistry.

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We describe the asymmetric total syntheses of naphthylisoquinoline alkaloids. Atroposelective biaryl coupling reaction between naphthyl pinacol boronate and an aryl iodide, bearing ()-2-aminopropyl group at the -position using the existing central chirality as an atroposelectivity-controlling group, provided the desired biaryl product with high atroposelectivity, without the use of an external chiral source. From the resulting biaryl product, several naphthylisoquinoline alkaloids were prepared via the stereoselective formation of the isoquinoline framework with the appropriate oxidation state and stereochemistry.

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Purpose: The purpose of this study to develop a fringed fall prevention program based on King's goal attainment theory and education. This study is applied to the personal, interpersonal, and social systems of fall high-risk patients to test its effects.

Methods: This study was a nonequivalent control group pre- and post-test design.

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A new protocol for the enantioselective synthesis of 3,3'-disubstituted-1,1'-bi-6-methoxy-2-phenol (BIPhOL) derivatives is described. Diastereomeric resolution of racemic BIPhOL boronic acid using a boronic acid moiety as a resolving group generated two diastereomers and subsequent Suzuki-Miyaura coupling reaction of the resulting diastereomers with aryl halides provided BIPhOL derivatives without any loss of enantioselectivity. In addition, the absolute stereochemistry of chiral BIPhOL was determined by comparison of the optical rotation with the reported value.

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A new method for the synthesis of chiral β-aryl amines via chiral phosphoric acid-catalyzed enantioselective reductive amination of benzyl methyl ketone derivatives with Hantzsch ester was developed. Various chiral β-aryl amines were obtained in high yields and with good to high enantioselectivities. This transformation is applicable to gram-scale reactions, and the catalyst loading can be reduced to 1 mol % without sacrificing any catalytic efficacy.

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The metal-free thermal protodeboronation of various electron-rich arene boronic acids was studied. Several reaction parameters controlling this protodeboronation, such as solvent, temperature, and a proton source, have been investigated. On the basis of these studies, suitable reaction conditions for protodeboronation of several types of electron-rich arene boronic acids were provided.

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The first metal-free thermal protodeboronation of ortho- and para-phenol boronic acids in DMSO was developed. The protodeboronation was successfully applied to the synthesis of ortho- and meta-functionalized phenols using the boronic acid moiety as a blocking group and a directing group, respectively. Mechanistic studies suggested that this protodeboronation proceeds through the coordination of water to the boron atom followed by σ-bond metathesis.

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A new concept of diastereomeric resolution has been developed where a boronic acid functionality was employed as (1) a diastereomeric resolving group with a chiral boron ligand and (2) a masked functional group for further transformation thereafter. This new diastereomeric resolution method was successfully applied to the preparation of both (R)- and (S)-3,3'-disubstituted 1,1'-bi-2-naphthol (BINOL) derivatives in a step-ecomonical manner. Racemic BINOL boronic acid reacted with a commercially available pinene-derived iminodiacetic acid as a chiral boron ligand to generate the two diastereomers in quantitative yields over a gram-scale quantity.

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