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Your search keyword '"Nagao, Kazunori"' showing total 244 results
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244 results on '"Nagao, Kazunori"'

2. Static to inducibly dynamic stereocontrol: The convergent use of racemic β-substituted ketones

Author

DeHovitz, Jacob S, Loh, Yong Yao, Kautzky, Jacob A, Nagao, Kazunori, Meichan, Andrew J, Yamauchi, Motoshi, MacMillan, David WC, and Hyster, Todd K

Subjects
Organic Chemistry, Chemical Sciences, General Science & Technology
Abstract

The synthesis of stereochemically complex molecules in the pharmaceutical and agrochemical industries requires precise control over each distinct stereocenter, a feat that can be challenging and time consuming using traditional asymmetric synthesis. Although stereoconvergent processes have the potential to streamline and simplify synthetic routes, they are currently limited by a narrow scope of inducibly dynamic stereocenters that can be readily epimerized. Here, we report the use of photoredox catalysis to enable the racemization of traditionally static, unreactive stereocenters through the intermediacy of prochiral radical species. This technology was applied in conjunction with biocatalysts such as ketoreductases and aminotransferases to realize stereoconvergent syntheses of stereodefined γ-substituted alcohols and amines from β-substituted ketones.

Published
2020

6. N‑Heterocyclic Carbene (NHC)/Metal Cooperative Catalysis

Author

Nagao, Kazunori, Ohmiya, Hirohisa, Olivucci, Massimo, Editor-in-Chief, Wong, Wai-Yeung, Editor-in-Chief, Bayley, Hagan, Series Editor, Hughes, Greg, Series Editor, Hunter, Christopher A., Series Editor, Hwang, Seong-Ju, Series Editor, Ishihara, Kazuaki, Series Editor, Kirchner, Barbara, Series Editor, Krische, Michael J., Series Editor, Larsen, Delmar, Series Editor, Lehn, Jean-Marie, Series Editor, Luque, Rafael, Series Editor, Siegel, Jay S., Series Editor, Thiem, Joachim, Series Editor, Venturi, Margherita, Series Editor, Wong, Chi-Huey, Series Editor, Wong, Henry N.C., Series Editor, Yam, Vivian Wing-Wah, Series Editor, Yan, Chunhua, Series Editor, You, Shu-Li, Series Editor, Arndtsen, Bruce A., editor, and Gong, Liu-Zhu, editor

Published
2020
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7. Deoxygenative Geminal Silylboration of Amides Using Silylboronates: Synthesis and Use of α‐Boryl‐α‐Silylalkylamines.

Author

Watanabe, Koh, Nagao, Kazunori, and Ohmiya, Hirohisa

Subjects
*BASE catalysts, *LEWIS bases, *AMIDES, *PROTON transfer reactions, *DRUGS
Abstract

α‐Silylalkylamines and α‐borylalkylamines are versatile synthetic intermediates and attractive scaffolds found in pharmaceutical drugs and agrochemicals. Despite great progress on synthetic methods for preparation of α‐silylalkylamines or α‐borylalkylamines, there are no general strategies for preparation of α‐boryl‐α‐silylalkylamines and the reactivity has not been explored. Here we report deoxygenative geminal silylboration of amides using silylboronates in the presence of alkoxide base catalyst, producing α‐boryl‐α‐silylalkylamines. The silicon and boron groups in α‐boryl‐α‐silylalkylamines are found to be utilized to chemoselective transformations, such as protonation and alkylation. This protocol serves various α‐silylalkylamines and α‐borylalkylamines from readily available amides. [ABSTRACT FROM AUTHOR]

Published
2024
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15. Synthesis of tertiary alkylphosphonate oligonucleotides through light-driven radical-polar crossover reactions

Author

50825164, 40508876, Ota, Kenji, Nagao, Kazunori, Hata, Dai, Sugiyama, Haruki, Segawa, Yasutomo, Tokunoh, Ryosuke, Seki, Tomohiro, Miyamoto, Naoya, Sasaki, Yusuke, Ohmiya, Hirohisa, 50825164, 40508876, Ota, Kenji, Nagao, Kazunori, Hata, Dai, Sugiyama, Haruki, Segawa, Yasutomo, Tokunoh, Ryosuke, Seki, Tomohiro, Miyamoto, Naoya, Sasaki, Yusuke, and Ohmiya, Hirohisa

Abstract

Chemical modification of nucleotides can improve the metabolic stability and target specificity of oligonucleotide therapeutics, and alkylphosphonates have been employed as charge-neutral replacements for naturally-occurring phosphodiester backbones in these compounds. However, at present, the alkyl moieties that can be attached to phosphorus atoms in these compounds are limited to methyl groups or primary/secondary alkyls, and such alkylphosphonate moieties can degrade during oligonucleotide synthesis. The present work demonstrates the tertiary alkylation of the phosphorus atoms of phosphites bearing two 2’-deoxynuclosides. This process utilizes a carbocation generated via a light-driven radical-polar crossover mechanism. This protocol provides tertiary alkylphosphonate structures that are difficult to synthesize using existing methods. The conversion of these species to oligonucleotides having charge-neutral alkylphosphonate linkages through a phosphoramidite-based approach was also confirmed in this study.

Published
2023

33. Photoredox-Catalyzed Site-Selective Intermolecular C(sp3)–H Alkylation of Tetrahydrofurfuryl Alcohol Derivatives

Author

Abe, Reiji, Nagao, Kazunori, Seki, Tomohiro, Hata, Dai, Sasaki, Yusuke, and Ohmiya, Hirohisa

Abstract

4′-Selective alkylation of nucleosides has been recognized as one of the ideal and straightforward approaches to chemically modified nucleosides, but such a transformation has been scarce and less explored. In this Letter, we combine a visible-light-mediated photoredox catalysis and hydrogen atom transfer (HAT) auxiliary to achieve β-C(sp3)–H alkylation of alcohol on tetrahydrofurfuryl alcohol scaffolds and exploit it for 4′-selective alkylation of nucleosides. The reaction involves an intramolecular 1,5-HAT process and stereocontrolled Giese addition of the resultant radicals.

Published
2025
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50. Copper-Catalyzed gamma-Selective and Stereospecific Allylic Cross-Coupling with Secondary Alkylboranes

Author

Yasuda, Yuto, Nagao, Kazunori, Shido, Yoshinori, Mori, Seiji, Ohmiya, Hirohisa, and Sawamura, Masaya

Subjects
copper catalysis, secondary alkylborane, allylic substitution, coupling, stereoselectivity
Abstract

The scope of the copper-catalyzed coupling reactions between organoboron compounds and allylic phosphates is expanded significantly by employing triphenylphosphine as a ligand for copper, allowing the use of secondary alkylboron compounds. The reaction proceeds with complete gamma-E-selectivity and preferential 1,3-syn stereoselectivity. The reaction of gamma-silicon-substituted allylic phosphates affords enantioenriched alpha-stereogenic allylsilanes.

Published
2015

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