Kei Kitamura

Bio: Kei Kitamura is an academic researcher from Kwansei Gakuin University. The author has contributed to research in topics: Aryne & Nucleophile. The author has an hindex of 5, co-authored 14 publications receiving 160 citations.

Total Synthesis of Aryl C-Glycoside Natural Products: Strategies and Tactics

Abstract: The aryl C-glycoside structure is, among the plenty of biologically active natural products, one of the distinct motifs embedded. Because of the potential bioactivity as well as the synthetic challenges, these structures have attracted considerable interest, and extensive research toward the total synthesis has been performed. This Review focuses on the synthetic strategies and tactics employed in the total synthesis of this class of natural products. The Introduction describes the historical background, structural features, and synthetic problems associated with aryl C-glycoside natural products. Next the Review summarizes the methods for constructing the aryl C-glycoside bonds. Completed total syntheses—and, in some cases, selected examples of incomplete syntheses—of natural aryl C-glycosides are also summarized. Finally described are the strategies for constructing polycyclic structures, which were utilized in the total syntheses.

1,3-Dialkynyl- and 1,3-Dialkenylisobenzofurans: New π-Extended Congeners Prepared by Double Nucleophilic Addition of Alkynyllithiums to o-Phthalaldehyde

Abstract: Efficient synthetic route to 1,3-dialkynyl- and 1,3-dialkenylisobenzofurans, new π-extended congeners of isobenzofurans, was reported. A three-step protocol including double nucleophilic additions of alkynyllithiums to o-phthalaldehyde and selective oxidation enables us to prepare various functionalized π-extended isobenzofurans. The photophysical properties of these π-extended isobenzofurans are also evaluated.

Synthesis and Evaluation of a 1,3a,6a-Triazapentalene (TAP)-Bonded System

Abstract: A method of synthesizing a directly connected 1,3a,6a-triazapentalene (TAP) ring system as a linearly bonded aromatic system with a planar form was established. Various TAP-dimers and a 2-alkyl-TAP-trimer were synthesized and their fluorescence properties were evaluated. Although the direct connection of the TAP ring with other TAP rings did not affect the fluorescence properties in diluted solvent, TAP-dimers showed unique fluorescence properties derived from the aggregation state under highly concentrated conditions. In particular, TAP-dimer 5f showed aggregation-induced emission in highly concentrated solution, and 5b showed typical mechanochromic fluorescence in the solid state despite their compact molecular size.

Efficient Bis-C-Aminoglycosylation toward the Synthesis of the Pluramycins

Abstract: Two bis-C-aminoglycosyl arenes containing the angolosamine and the vancosamine moieties, which are potentially useful as the D-ring fragments of the pluramycin-type antibiotics, were efficiently synthesized by the O→C-glycoside rearrangement based strategy.

Recent Advances in the Chemical Synthesis of C-Glycosides

Abstract: Advances in the chemical synthesis of C-pyranosides/furanosides are summarized, covering the literature from 2000 to 2016. The majority of the methods take advantage of the construction of the glycosidic C—C bond. These C-glycosylation methods are categorized herein in terms of the glycosyl donor precursors, which are commonly used in O-glycoside synthesis and are easily accessible to nonspecialists. They include glycosyl halides, glycals, sugar acetates, sugar lactols, sugar lactones, 1,2-anhydro sugars, thioglycosides/sulfoxides/sulfones, selenoglycosides/telluroglycosides, methyl glycosides, and glycosyl imidates/phosphates. Mechanistically, C-glycosylation reactions can involve glycosyl electrophilic/cationic species, anionic species, radical species, or transition-metal complexes, which are discussed as subcategories under each type of sugar precursor. Moreover, intramolecular rearrangements, such as the Claisen rearrangement, Ramberg–Backlund rearrangement, and 1,2-Wittig rearrangement, which usuall...

Total Synthesis of Aryl C-Glycoside Natural Products: Strategies and Tactics

Abstract: The aryl C-glycoside structure is, among the plenty of biologically active natural products, one of the distinct motifs embedded. Because of the potential bioactivity as well as the synthetic challenges, these structures have attracted considerable interest, and extensive research toward the total synthesis has been performed. This Review focuses on the synthetic strategies and tactics employed in the total synthesis of this class of natural products. The Introduction describes the historical background, structural features, and synthetic problems associated with aryl C-glycoside natural products. Next the Review summarizes the methods for constructing the aryl C-glycoside bonds. Completed total syntheses—and, in some cases, selected examples of incomplete syntheses—of natural aryl C-glycosides are also summarized. Finally described are the strategies for constructing polycyclic structures, which were utilized in the total syntheses.

Recent Advances in Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds.

Abstract: This review surveys recent progress in the chemistry of polycyclic heteroaromatic molecules with a focus on structural diversity and synthetic methodology. The article covers literature published during the period of 2016-2020, providing an update to our first review of this topic (Chem. Rev.2017, 117 (4), 3479-3716).

Aryne-based strategy in the total synthesis of naturally occurring polycyclic compounds.

Abstract: The total syntheses of polycyclic natural products by exploiting an aryne as the key reactive species are reviewed. A short introduction summarizes the basic reactivities of aryne species as well as the methods for its generation. In the main part, early examples and the recent reports (mainly 2012–present) on the use of arynes in multistep syntheses are described.

Palladium-catalysed C−H glycosylation for synthesis of C-aryl glycosides

Abstract: C-aryl glycosides are widely found in nature and play important roles in drug design. Despite the significant progress made over the past few decades, efficient and stereoselective synthesis of complex C-aryl glycosides remains challenging, lagging far behind the state of the art of the synthesis of O- or N-glycosides. Here, we report a simple and powerful bioinspired strategy for the stereoselective synthesis of C-aryl glycosides via palladium-catalysed ortho-directed C(sp2)−H functionalization of arenes and heteroarenes with easily accessible glycosyl chloride donors. The catalytic palladacycle intermediate generated via C−H palladation provides a soft aryl nucleophile that can react with glycosyl oxocarbenium ion partners with high efficiency and excellent stereocontrol. The method can be applied to a wide range of arene and heteroarene substrates, glycosyl chloride donors and auxiliary groups. It can simplify the synthesis of a variety of complex C-aryl glycosides and offers a tool for late-stage modification of drug molecules. C-aryl glycosides are present in many natural products and of interest in drug design, but their chemical synthesis is challenging. This work reports an efficient and diastereoselective ortho-directed C−H glycosylation of arenes and heteroarenes with glycosyl chloride using a palladium catalyst.