Monday, April 11, 2016
Douglass F. Taber
University of Delaware
C-O Ring Construction: The Shi Synthesis of Ipomoeassin F
J. C.-Y. Lee of the University of Hong Kong and Camille Oger and Jean-Marie Galano of the Université de Montpellier effected (Chem. Commun. 2015, 51, 15696. ) Payne rearrangement of the symmetrical bis-epoxide derived from 1 (SAE) to give an intermediate that cyclized to 2. Chang-Hua Ding and Xue-Long Hou of the Shanghai Institute of Organic Chemistry (Chem. Commun. 2015, 51, 12235. ) and Clément Mazet of the University of Geneva (Chem. Sci. 2015, 6, 4807. ) added 4 to 3 to give 2,5-dihydrofuran 5 in high ee. Stanley P. Kolis of Lilly cyclized (Org. Process Res. Dev. 2015, 19, 1203. ) the nitrone derived from 6 and 7 to 8 in high de. Christopher J. Moody of the University of Nottingham (Angew. Chem. Int. Ed. 2015, 54, 8485. ) and Dong Xing and Wenhao Hu of the East China Normal University (Chem. Eur. J. 2015, 21, 19202. ) developed the cascade cyclization of 9 with 10 to give 11. Professor Hu (Chem. Commun. 2015, 51, 15204. ) and Tao Wang and Zunting Zhang of Shaanxi Normal University (Org. Lett. 2015, 17, 5124. ) added 13 to 12 to form the dihydrofuran 14.
Li-Na Guo of Xi'an Jiaotong University observed (Synthesis 2015, 47, 3191. ) that K2S2O8 was sufficient to oxidize 15 to the corresponding radical, that added to 16 to give, after another oxidation, the 2,3-dihydrofuran 17. Such oxidations have in the past been carried out with Mn(OAc)3. It will be interesting to see if the inclusion of catalytic Cu(II) can extend the range of the K2S2O8 cyclizations, as it does for Mn(OAc)3.
Kegong Ji of Northwest A&F University oxidatively cyclized (Chem. Commun. 2015, 51, 10318. ) the diyne 18 to the enone 19. Xinghua Zhang of the Shanghai Institute of Technology and Qun Qian and Hegui Gong of Shanghai University coupled (Chem. Commun. 2015, 51, 10302. ) the bromide 20 with benzoic anhydride to give the ketone 21. Simon Wagschal and Sébastien Lemaire of Janssen Pharmaceutica found (J. Org. Chem. 2015, 80, 9328. ) that opening of the epoxide 22, readily prepared with in situ generated dimethyldioxirane, with 23 proceeded with net retention of absolute configuration, leading to 24. Debendra K. Mohapatra of the Indian Institute of Chemical Technology prepared (Tetrahedron Lett. 2015, 56, 5930. ) 27 by cyclizing 25 with 26 and iodine.
En route to (-)-Aplysiallene, Hiromichi Fujioka of Osaka University found (J. Org. Chem. 2015, 80, 10261. ) that 28 could be cyclized to 29 with high diastereocontrol. Adrien Quintard and Jean Rodriguez of Aix Marseille Université constructed (Eur. J. Org. Chem. 2015, 5709. ) the macrolactone 31 by reduction of 30 followed by fragmentation.
Ipomoeassin F (34), a glycoresin isolated from the leaves of Ipomoea squamosa of the Suriname rainforest, showed single-digit nanomolar activity against selected human cancer cell lines. Wei Q. Shi of the University of Arkansas devised (J. Org. Chem. 2015, 80, 9279. ) an efficient assembly of the precursor 32, and showed that it could be cleanly cyclized to 33.
D. F. Taber, Org. Chem. Highlights 2016, April 11.