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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. ) 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. ) 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. ) the selective conversion of 6 to 7. Berit Olofsson of Stockholm University showed (Org. Lett. 2016, 18, 4234. ) 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. ) 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. ) 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. ) 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. ) 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. ) 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. ) 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. ) 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. ) 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. ) 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. ) the selective deactylation of 29 to 30.

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