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Monday, June 12, 2017
Douglass F. Taber
University of Delaware

Functional Group Protecting: The Li/Wang Synthesis of Ganocin B

Sobi Asako and Kazuhiko Takai of Okayama University deoxygenated the epoxide 1 to 2 (Adv. Synth. Catal. 2016, 358, 3966. DOI: 10.1002/adsc.201600840) with inversion of alkene geometry. With an alternative ligand, the deoxygenation proceeded with retention of alkene geometry. Xigeng Zhou of Fudan University used (Angew. Chem. Int. Ed. 2016, 55, 11485. DOI: 10.1002/anie.201605822) exchange with a sacrificial alkyne 4 to deprotect 3 to 5. Zhen Yang and Yong Huang of Peking University Shenzhen Graduate School effected (Angew. Chem. Int. Ed. 2016, 55, 14340. DOI: 10.1002/anie.201608974) the selective conversion of 6 to 7. Berit Olofsson of Stockholm University showed (Org. Lett. 2016, 18, 4234. DOI: 10.1021/acs.orglett.6b01975) that even a very congested alcohol 8 could be converted into the corresponding aryl ether 9 using a hypervalent iodine reagent. Alexandre Gagnon of the Université du Québec à Montréal found (Tetrahedron Lett. 2016, 57, 4284. DOI: 10.1016/j.tetlet.2016.08.021) that using a triarylbismuthine (not illustrated) a primary alcohol could be converted into the aryl ether in the presence of a secondary alcohol.

Munetaka Kunishima of Kanazawa University developed (Eur. J. Org. Chem. 2016, 4093. DOI: 10.1002/ejoc.201600663) the reagent 11 for the conversion of an alcohol 10 to the t-butyl ether 12. Acids were also converted to t-butyl esters. Robert H. Grubbs of Caltech protected (Org. Lett. 2016, 18, 5776. DOI: 10.1021/acs.orglett.6b01687) the diol 13 as the bridging silyl ether 15 using 14 with NaOH as the catalyst.

Methyl ethers are notoriously robust. Zhong-jun Li of the Peking University Health Science Center devised (Tetrahedron 2016, 72, 5699. DOI: 10.1016/j.tet.2016.07.081) a protocol for the conversion of 16 to 17. Raul SanMartin and Esther Domínguez of the University of the Basque Country established (Adv. Synth. Catal. 2016, 358, 3307. DOI: 10.1002/adsc.201600593) conditions for the oxidative deprotection of benzyl ether 18 to 19.

Eelco Ruijter and Romano V. A. Orru of the Vrije Universiteit Amsterdam observed (Org. Lett. 2016, 18, 3562. DOI: 10.1021/acs.orglett.6b01481) that trityl isontrile could serve as the donor for the conversion of the aldehyde 20 to the protected cyanohydrin 21. Sung Yun Yang of Chungnam National University and Ji-Woong Park of the Gwangju Institute of Science and Technology showed (Angew. Chem. Int. Ed. 2016, 55, 11495. DOI: 10.1002/anie.201605609) that lipase loaded onto a nanoporous covalent framework film maintained indefinitely its activity for the conversion of 22 to 23. Marcin K. Chmielewski of the Polish Academy of Sciences demonstrated (Org. Lett. 2016, 18, 3230. DOI: 10.1021/acs.orglett.6b01475) that the ester 24 was deprotected to the acid 25 on gentle warming under neutral conditions. Professor Kuneshima also developed (Chem. Eur. J. 2016, 22, 14042. DOI: 10.1002/chem.201603120) the reagent 27 for the conversion of an amide 26 to the benzyl ester 28.

Ganocin B (31), isolated from the fruiting bodies of the fungus Ganoderma cochlear, showed anti-AChE activity. En route to 31, Qingjiang Li and Honggen Wang of Sun Yat-sen University effected (Org. Biomol. Chem. 2016, 14, 10362. DOI: 10.1039/C6OB02049F) the selective deactylation of 29 to 30.

D. F. Taber, Org. Chem. Highlights 2017, June 12.