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Monday, November 14, 2016
Douglass F. Taber
University of Delaware

C-O Ring Construction: The Kang/Lee Synthesis of (-)-11β-Hydroxycurvularin

In the course of a synthesis of the unusual diterpene dictyoxetane, Thomas Magauer of the Ludwig-Maximilians-University Munich cyclized (J. Am. Chem. Soc. 2016, 138, 6420. DOI: 10.1021/jacs.6b03720) the diol 1 to 2. Drawing on older work, Guang-Fu Yang of Central China Normal University rearranged (Org. Biomol. Chem. 2016, 14, 3482. DOI: 10.1039/C6OB00371K) the lactone 3 to the oxetane 4.

Yannick Landais of the University of Bordeaux developed (Org. Lett. 2016, 18, 1542. DOI: 10.1021/acs.orglett.6b00303) the radical addition of 6 to 5, leading, via acid-mediated cyclization, to the ester 7. Kazuaki Ishihara of Nagoya University devised (Chem. Lett. 2016, 45, 353. DOI: 10.1246/cl.160004) the enantioselective oxidative cyclization of 8 to 9. Zhongwen Wang of Nankai University constructed (Eur. J. Org. Chem. 2016, 2467. DOI: 10.1002/ejoc.201600233) 12 by combining 10 with 11. Nuno Maulide of the Universität Wien reported (Angew. Chem. Int. Ed. 2016, 55, 6780. DOI: 10.1002/anie.201601340) related results (not illustrated). En route to laidlomycin, Hee-Seung Lee and Sung Ho Kang of KAIST observed (Chem. Commun. 2016, 52, 3536. DOI: 10.1039/C5CC10673G) high diastereoselectivity in the oxidative cyclization of 13 to 14.

Brian M. Stoltz of Caltech established (Angew. Chem. Int. Ed. 2016, 55, 7437. DOI: 10.1002/anie.201601991) a general route to cyclic enol ethers, illustrated by the conversion of 15 to 3,4-dihydro-
16. B. V. Subba Reddy of the Indian Institute of Chemical Technology prepared (Tetrahedron Lett. 2016, 57, 1889. DOI: 10.1016/j.tetlet.2016.03.062) 18 by the combination of 17 with 11. Monique Mathé-Allainmat of the Université de Nantes showed (Tetrahedron 2016, 72, 318. DOI: 10.1016/j.tet.2015.11.046) that the iodide from the combination of 19 with 20 eliminated to give the alkene 21 with high regioselectivity. Sergio J. Álvarez-Méndez and Victor S. Martin of the Universidad de La Laguna found (Chem. Commun. 2016, 52, 3380. DOI: 10.1039/C6CC00160B) that the acyl oxazolidinone of 22 guided the condensation with 23, leading to 24. Presumably beginning with the enantiopure substituted (Evans) oxazolidinone would result in 24 with similar diastereocontrol.

Arun K. Ghosh of Purdue University assembled (Org. Lett. 2016, 18, 396. DOI: 10.1021/acs.orglett.5b03411) the oxocene 27 by combining 25 with 26. Asuncíon Barbero of the Campus Migeul Delibes described (J. Org. Chem. 2016, 81, 2704. DOI: 10.1021/acs.joc.5b02260) related results (not illustrated). Rongbiao Tong of the Hong Kong University of Science and Technology effected (J. Org. Chem. 2016, 81, 4325. DOI: 10.1021/acs.joc.6b00788) the oxidative cleavage of 28 to the medium ring lactone 29.

The macrolide (-)-11β-hydroxycurvularin (32) has anti-tumor and anti-inflammatory activity. In the course of a synthesis of 32, Young Kee Kang of Chungbuk National University and Jongkook Lee of Kangwon National University took advantage (J. Org. Chem. 2016, 81, 2612. DOI: 10.1021/acs.joc.5b02760) of the highly ordered transition state of an intramolecular dipolar cycloaddition, converting 30 to 31 with high diastereocontrol.

D. F. Taber, Org. Chem. Highlights 2016, November 14.