Winding vine-shaped molecular asymmetry is induced by enantioselective ring-closing metathesis with a chiral molybdenum catalyst. The reaction proceeds under mild conditions through an E-selective ring-closing metathesis leading to macrocyclic bisazoles with enantioselectivities of up to 96% ee.
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http://dx.doi.org/10.1002/anie.201500459 | DOI Listing |
J Org Chem
December 2024
Department of Applied Chemistry, Faculty of Science and Engineering, Chuo University, 1-13-27 Kasuga, Bunkyo-ku, Tokyo 112-8551, Japan.
(-)-Exiguolide is a marine macrolide natural product with potent anticancer activity. In this study, the total synthesis of exiguolide stereoisomers, (9)-exiguolide, (9,13)-exiguolide, and (9,13,19)-exiguolide, was achieved by capitalizing on our macrocyclization/transannular pyran cyclization strategy. The impact of the stereochemical permutation on the reactivity of advanced intermediates, the conformation of the macrocyclic skeleton, and the antiproliferative activity against human cancer cells were investigated in detail.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
State Key Laboratory of Natural and Biomimetic Drugs, School of Pharmaceutical Sciences, and Chemical Biology Center, Peking University, 38 Xueyuan Road, Beijing 100191, China.
Angew Chem Int Ed Engl
November 2024
State Key Laboratory of Applied Organic Chemistry and College of Chemistry and Chemical Engineering, Lanzhou University, 222 South Tianshui Road, Lanzhou, Gansu Province, 730000, China.
Kalmanol (1) is the first isolated kalmane-type grayanoid featuring a highly oxidized 5/8/5/5 tetracyclic carbon skeleton and 9 contiguous stereocenters. We have accomplished the efficient and asymmetric total synthesis of 1 in 16 steps from known compounds (20 steps from commercially available starting materials) by a modular synthetic strategy. A tetracyclic intermediate was prepared in a convergent manner through a Grignard reaction and a subsequent ring-closing metathesis reaction of two enantiomerically enriched fragments.
View Article and Find Full Text PDFRSC Adv
November 2024
Department of Biochemistry and Molecular Biotechnology, University of Massachusetts Chan Medical School Worcester Massachusetts 01605 USA +1 508 856 8873.
A new and highly efficient ring-closing metathesis-based strategy was developed for the synthesis of the cyclic urea 1,3-diazepinone, presenting significant improvement upon previous methods. Using a direct glycosylation approach, analogues of the potent cytidine deaminase (CDA) inhibitor diazepinone riboside were then synthesized including 2'-deoxyribo-, 2'-deoxy-2'-fluoroarabino-, and 2'-deoxy-2',2'-difluoro-diazepinone nucleosides, all with moderate to good yield and excellent anomeric selectivity. Crucially, in contrast to the previous multistep linear synthesis of 2'-deoxyribo- and 2'-deoxy-2'-fluoroarabino-diazepinone nucleosides, this is the first report of direct glycosylation to access these nucleosides.
View Article and Find Full Text PDFRSC Adv
November 2024
Zeon Corporation R&D Center 1-2-1 Yako, Kawasaki-ward Kawasaki-city Kanagawa-pref. 210-9507 Japan +81-44-276-3957 +81-80-1006-7136.
Herein, we report a study on the preparation, properties, and depolymerization of pristine and vulcanized poly(cyclopentene) (poly(CP)), poly(norbornene--cyclopentene) (poly(NB--CP)) and poly(-dicyclopentadiene--cyclopentene) (poly (DCP--CP)). First, poly(CP), poly(NB--CP) and poly(DCP--CP) were prepared with high molecular weight control ( = 200 000-500 000) using dichloro(3-phenyl-1-inden-1-ylidene)bis(tricyclohexylphosphine)ruthenium(ii). Next, carbon black, zinc oxide and other additives were blended into the pristine polymers using a mixer and twin roll rubber mills at 50 °C, followed by vulcanization in metal molds at 160 °C for 10 min, resulting in molded black rubber specimens.
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