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Monday, April 9, 2018
Douglass F. Taber
University of Delaware

C-O Ring Construction: The Carreira Synthesis of (+)-Broussonetine H

Mark S. Taylor of the University of Toronto showed (J. Org. Chem. 2017, 82, 11406. ) that by including phenylboronic acid, mannose (1) could be cleanly converted into the furanoside 2. Giuseppe Zanoni of the University of Pavia and Liming Zhang of the University of California, Santa Barbara devised (J. Am. Chem. Soc. 2017, 139, 16064. ) a gold catalyst that, depending on the enantiomer used, could cyclize 3 to either diastereomer of 4. Oleg V. Larionov of the University of Texas, San Antonio rearranged (J. Am. Chem. Soc. 2017, 139, 11365. ) 5 to 6, with control of two new stereogenic centers. Chang-Hua Ding and Xue-Long Hou of the Shanghai Institute of Organic Chemistry and Qian Peng of Nankai University assembled (Org. Lett. 2017, 19, 6658. ) 9 by combining 7 with the racemic epoxide 8.

Benjamin List of the Max-Planck-Institut für Kohlenforschung developed (J. Am. Chem. Soc. 2017, 139, 13656. ) an organocatalyst that mediated the asymmetric addition of 10 to 11 to give 12. Sehoon Park and Sukbok Chang of KAIST reduced (Angew. Chem. Int. Ed. 2017, 56, 13757. ) 13 selectively to 14. Damien Bonne and Jean Rodriguez of Aix Marseille University combined (Adv. Synth. Catal. 2017, 359, 3638. ) 15 with 16 to give an adduct that could be reduced selectively to 17. Paul E. Floreancig of the University of Pittsburgh cyclized (Angew. Chem. Int. Ed. 2017, 56, 10900. ) the alcohol mixture 18 to 19 as the dominant diastereomer.

Pedro O. Miranda and Juan I. Padrón of the Insituto de Productos Naturales y Agrobiología effected (Org. Lett. 2017, 19, 4834. ) the Prins cyclization of 20 with 21 to give the dichloride 22. Keisuke Asano and Seijiro Matsubara of Kyoto University used (Nature Commun. 2017, 8, 1397. ) 24 to generate the cyanohydrin from 23 under conditions that led to cyclization to 25.

Masahiro Miyazawa of the University of Toyama observed (Heterocycles 2017, 94, 1885. ) a mixture of diastereomers from the cyclization of 26 to 27, suggesting that this could be a good candidate for control by a stereodefined catalyst. Robert H. Grubbs of Caltech designed (Angew. Chem. Int. Ed. 2017, 56, 11213. ) a Ru catalyst that cyclized 28 cleanly to (Z)-29.

Broussonetine H (32), isolated from the mulberry tree Broussonetia kazinoki, is a potent glycosidase inhibitor. Using the spiroketalization of 30 to 31 that they had developed, Eric M. Carreira of the ETH Zürich was able (Org. Lett. 2017, 19, 5533. ) to establish the correct relative and absolute configuration of 32.

D. F. Taber, Org. Chem. Highlights 2017, April 9.
URL: https://www.organic-chemistry.org/Highlights/2018/09April.shtm