C-O Ring Construction: The Reber Synthesis of Clerobungin A
James A. Bull of Imperial College London demonstrated (Chem. Eur. J. 2016, 22, 16271. DOI: 10.1002/chem.201604031) the Friedel-Crafts alkylation of 2 with the oxetan-3-ol 1 to give the oxetane 3. Yu-Jang Li of National Chiayi University cyclized (Chem. Commun. 2016, 52, 12108. DOI: 10.1039/C6CC06857J) the enamine 4 to the oxetane 5.
Marco A. B. Ferreira of the Federal University of São Carlos used (Tetrahedron Lett. 2016, 57, 3334. DOI: 10.1016/j.tetlet.2016.06.064) the diene 7 to mediate the oxidative Co-catalyzed cyclization of 6 to 8. Benjamin List of the Max-Planck-Institut für Kohlenforschung optimized (J. Am. Chem. Soc. 2016, 138, 14538. DOI: 10.1021/jacs.6b09129) a catalyst for the enantioselective Prins addition of 10 to 9 to give 11. Michael K. Hilinski of the University of Virginia assembled (Eur. J. Org. Chem. 2016, 3335. DOI: 10.1002/ejoc.201600651) tetrahydrofuran 14 by adding the epoxide 12 to 13. Jun'ichi Uenishi of Kyoto Pharmaceutical University observed (J. Org. Chem. 2016, 81, 7471. DOI: 10.1021/acs.joc.6b01154) that the diastereomer 15 cyclized to 16.
Professor List showed (J. Am. Chem. Soc. 2016, 138, 10822. DOI: 10.1021/jacs.6b07240) that the catalyst family that was effective for the the combination of 9 with 10 to make 11 also promoted the addition of 18 to 17 leading to 19. Michael C. Willis and Andrew S. Weller of the University of Oxford developed (Angew. Chem. Int. Ed. 2015, 54, 8520. DOI: 10.1002/anie.201503208) a Rh catalyst that mediated the formation of 22 by the addition of 21 to 20. Xiaodong Shi of the University of South Florida effected (Org. Lett. 2016, 18, 6336. DOI: 10.1021/acs.orglett.6b03228) the complementary coupling of 24 with 23 to give 25. Rainer Mahrwald of Humboldt University prepared (Eur. J. Org. Chem. 2016, 5309. DOI: 10.1002/ejoc.201601058) 27 by the addition of acetone to 26. Yohei Shimizu and Motomu Kanai of the University of Tokyo reported (ACS Catal. 2016, 6, 6718. DOI: 10.1021/acscatal.6b02106) related results.
Biaolin Yin of the South China University of Science and Technology constructed (Org. Lett. 2016, 18, 3226. DOI: 10.1021/acs.orglett.6b01472) the spiroketal 30 by adding the boronic acid 29 to 28 under oxidative conditions. Indrajeet Sharma of the University of Oklahoma devised (Org. Lett. 2016, 18, 6340. DOI: 10.1021/acs.orglett.6b03229) the cascade addition of the diazo ester 32 to the hydroxy enone 31, leading via Cope rearrangement to the macrocyclic lactone 33.
The biosynthetically-interesting spiroacetal clerobungin A (36) was isolated from the shrub Clerodendrum bungei as a near-racemic mixture. Keith P. Reber of Towson University devised (J. Org. Chem. 2016, 81, 12006. DOI: 10.1021/acs.joc.6b02261) a simple route to 36, based on the cyclization of 34 to 35.