Kei Makita

Bio: Kei Makita is an academic researcher from Tohoku University. The author has contributed to research in topics: Michael reaction & Intramolecular force. The author has an hindex of 7, co-authored 14 publications receiving 183 citations.

Synthesis of polycyclic cyclobutane derivatives by tandem intramolecular Michael-aldol reaction under two complementary conditions: TBDMSOTf-Et3N and TMSI-(TMS)2NH

Abstract: The treatment of α,β-unsaturated esters having a ketone function at an appropriate position with either TBDMSOTf in the presence of Et 3 N or TMSI in the presence of (TMS) 2 NH provided, via a tandem intramolecular Michael-aldol reaction sequence, several different types of cyclobutane derivatives. The two reaction conditions were complementary. Tricyclo[4.2.1.03-8]nonanes 34 and 35, tricyclo[5.1.1.0 3,8 ]nonane 40, tricyclo[5.4.0.0 3,7 ]undecane 51, tetracyclo[5.4.0.0 3,7 .0 9,11 ]undecane 45, and the bicyclo[3.2.0]heptanes 36, 57, and 38, which have structures either partially or completely similar to those of endiandric acids A (1a), B (1b), and C (2), trihydroxydecipiadiene (3), lintenone (4), italicene (3), and filifolone (6), were stereoselectively synthesized by the tandem reaction

Facile Construction of the Tricyclo[5.2.1.01,5]decane Ring System by Intramolecular Double Michael Reaction: Highly Stereocontrolled Total Synthesis of (±)-8,14-Cedranediol and (±)-8,14-Cedranoxide

Abstract: It was observed that the synthesis of tricyclo[5.2.1.01,5]decane 10 can be performed effectively by the intramolecular double Michael reaction of 5-(5-methoxycarbonyl-4-pentenyl)-2-cyclopenten-1-one (9). Highly stereocontrolled total syntheses of (±)-8,14-cedranediol (2) and (±)-8,14-cedranoxide (1) were accomplished by the application of this methodology. Heating 5-(1,5-dimethyl-5-ethoxycarbonylpent-4-enyl)-2-cyclopenten-1-one (15) with TMSCl, Et3N, and ZnCl2 in o-dichlorobenzene at 150 °C provided (±)-(1R*,2R*,5R*,6R*,7S*)-2,6-dimethyl-6-ethoxycarbonyltricyclo[5.2.1.01,5]-decan-9-one (16) as a single isomer. The product 16 was stereoselectively converted into the above cedranoids 2 and 1 through ring expansion chemistry.

Total synthesis of (+/-)-culmorin and (+/-)-longiborneol: an efficient construction of Tricyclo[6.3.0.0(3,9)]undecan-10-one by intramolecular double Michael addition.

Abstract: The treatment of 4-[(5E)-6-methoxycarbonyl-5-hexenyl]-3, 4-dimethyl-2-cyclopenten-1-one (5) with LHMDS, TMSI-HMDS, Bu(2)OTf-HMDS, or TMSCl-NEt(3)-ZnCl(2) caused the intramolecular double Michael addition to afford tricyclo[6.3.0.0(3, 9)]undecan-10-one 12 in high yields with perfect stereoselectivity. The methodology was further elaborated to achieve efficient total syntheses of (+/-)-culmorin (1) and (+/-)-longiborneol (2). The common precursor 13 of them was obtained from 14 in 94% yield as a single isomer by the treatment with LHMDS. After the conversion of 13 into the corresponding acid 24 by hydrolysis, oxidative decarboxylation using S-(1-oxido-2-pyridinyl)-1,1,3, 3-tetramethylthiouronium hexafluorophosphate (HOTT, 27), followed by the Birch reduction, stereoselectively afforded (+/-)-culmorin (1). (+/-)-Longiborneol (2) was synthesized from 24 by the standard transformation. Additionally, the treatment of 24 with Pb(OAc)(4) led to 28 via uncommon migration. Its structure was determined by X-ray analysis after the transformation into the diketone 29.

Domino Reactions in Organic Synthesis

Abstract: Introduction Cationic domino reactions Anionic domino reactions Radical domino reactions Pericyclic domino reactions Photochemically induced domino processes Transition metal catalysis Domino reactions initiated by oxidation or reduction Enzymes in domino reactions Multicomponent reactions Special techniques in domino reactions

Nitric Oxide in Biological Denitrification: Fe/Cu Metalloenzyme and Metal Complex NOx Redox Chemistry

Abstract: Department of Chemistry, The Johns Hopkins University, Charles and 34th Streets, Baltimore, Maryland 21218, Kluyver Laboratory for Biotechnology, Delft University of Technology, 2628 BC Delft, The Netherlands, Department of Biochemistry and Molecular Biology, OGI School of Science and Engineering at OHSU, Beaverton, Oregon 97006, and Department of Microbiology and Molecular Genetics, University of California, Los Angeles, California 90095