C-O Ring Construction: The Silipo/Yu Synthesis of Forsythenethoside A

Lin Hu of Chongqing University observed high diastereoselectivity in the assembly of 3 by the addition of 1 to 2 (Org. Lett. 2019, 21, 5679. DOI: 10.1021/acs.orglett.9b02012). Patrick H. Dussault of the University of Nebraska reported related results (J. Org. Chem. 2019, 84, 14611. DOI: 10.1021/acs.joc.9b02112). Christoph Schneider of the University of Leipzig prepared the tetrahydrofuran 7 by adding 5, then 6 to 4 under flow conditions (Eur. J. Org. Chem. 2019, 5326. DOI: 10.1002/ejoc.201900421). Xinfang Xu of Sun Yat-sen University and Rene M. Koenigs of RWTH Aachen used visible light to promote the combination of the diazoester 8 with the oxetane 9, leading to 10 (Chem. Sci. 2019, 10, 10129. DOI: 10.1039/C9SC04069B). Liming Zhang of the University of California, Santa Barbara rearranged 11 cleanly to the butenolide 12 (ACS Catal. 2019, 9, 10339. DOI: 10.1021/acscatal.9b03501).

Yoshihiro Nishimoto and Makoto Yasuda of Osaka University cyclized 13 to 14 (J. Org. Chem. 2019, 84, 14330. DOI: 10.1021/acs.joc.9b02186). You Yang of the East China University of Science and Technology described a parallel investigation (J. Org. Chem. 2019, 84, 14141. DOI: 10.1021/acs.joc.9b01582). Scott E. Denmark of the University of Illinois achieved high enantioselectivity in the preparation of the tetrahydropyran 17 by the cyclization of 15 with 16 (Angew. Chem. Int. Ed. 2019, 58, 12486. DOI: 10.1002/anie.201906535). Atsushi Ueda and Masakazu Tanaka of Nagasaki University combined 18, prepared by enantioselective conjugate addition, with 19, leading to 20 (Heterocycles 2019, 99, 989. DOI: 10.3987/COM-18-S(F)63, Link). Gang He and Gong Chen of Nankai University prepared 23 by coupling 21 with 22 (Nature Catal. 2019, 2, 793. DOI: 10.1038/s41929-019-0324-5).

Fuyuhiko Inagaki of Kobe Gakuin University showed that a silver catalyst would cyclize 24 to 25 (Tetrahedron Lett. 2019, 60, 151038. DOI: 10.1016/j.tetlet.2019.151038). Michael R. Buchmeiser of the University of Stuttgart devised a macroporous silica catalyst that confined 26, enabling efficient cyclization to the macrocycle 27 (J. Am. Chem. Soc. 2019, 141, 19014. DOI: 10.1021/jacs.9b08776). Barry M. Trost of Stanford University cyclized 28 to 29 in high ee (J. Am. Chem. Soc. 2019, 141, 10199. DOI: 10.1021/jacs.9b06050). Lijia Wang of East China Normal University assembled 33 by combining 30, 31, and 32 (Angew. Chem. Int. Ed. 2019, 58, 15016. DOI: 10.1002/anie.201907353).

The neuroprotective forsythenethoside A (35) was isolated from the East Asian medicinal herb Forsynthia suspensa. Alba Silipo of the University of Naples "Federico II" and Biao Yu of the Shanghai Institute of Organic Chemistry prepared 35 by the oxidative cyclization of 34, followed by selective deprotection (J. Org. Chem. 2019, 84, 13733. DOI: 10.1021/acs.joc.9b01956).