Monday, July 23, 2018
Douglass F. Taber
University of Delaware
Arrays of Stereogenic Centers: The Wu Synthesis of Neomaclafungin A
Xiaoming Feng of Sichuan University converted the enone 1 to the bromo azide 2 (J. Am. Chem. Soc. 2017, 139, 13414. ). Professor Feng and Lili Lin, also of Sichuan University, achieved high ee in the epoxidation of 3 to 4 (Adv. Synth. Catal. 2017, 359, 3454. ). Ayyanar Siva of Madurai Kamaraj University constructed the epoxide 7 by the Darzens condensation of 6 with the aldehyde 5 (Chem. Commun. 2017, 53, 10926. ). In a modified Mannich reaction, Yingjie Lin and Haifeng Duan of Jilin University added 9 to 8, leading to 10 (Adv. Synth. Catal. 2017, 359, 4111. ).
Tomoya Miura and Masahiro Murakami of Kyoto University showed that under Ru catalysis, the alkene of 12 migrated to form the allyl borane, that then added to the aldehyde 11 to give 13 (J. Am. Chem. Soc. 2017, 139, 10903. ). Jennifer M. Schomaker of the University of Wisconsin cyclized 14 in high ee, then opened the resulting aziridine, leading to 15 (Angew. Chem. Int. Ed. 2017, 56, 9944. ). X. Peter Zhang of Boston College reported a related asymmetric intramolecular aziridination using a Co catalyst (J. Am. Chem. Soc. 2017, 139, 9164. ). Matthias C. McIntosh of the University of Arkansas observed high diastereoselectivity in the reduction of 16, leading, after rearrangement of the intermediate allyl diazene, to the ether 17 (J. Org. Chem. 2017, 82, 8359. ). Masatoshi Murataka of Chugai Pharmaceutical Co. optimized the Ireland-Claisen rearrangement of 18 to 19 (Org. Biomol. Chem. 2017, 15, 6632. ).
Dieter Enders of RWTH Aachen University achieved high relative and absolute stereocontrol in the addition of 21 to 20 to give 22 (Chem. Eur. J. 2017, 23, 13042. ). Regan J. Thomson of Northwestern University and Scott E. Schauss of Boston University coupled 23 with 24 to give the diene 25 (Angew. Chem. Int. Ed. 2017, 56, 16631. ). Łukasz Albrecht of Lodz University of Technology combined 26 with 27 to give 28, with a stereodefined alkylated quaternary center (Chem. Commun. 2017, 53, 11472. ). Thomas C. Nugent of Jacobs University also developed what appears to be a general route to stereodefined quaternary centers, adding 29 to 30 to give 31 (Adv. Synth. Catal. 2017, 359, 2824).).
Neomaclafungin A (35), isolated from the bacterium Actinoalloteichus sp. NPS702 found in marine sediment, shows significant antifungal activity. En route to 35, Yikang Wu of the Shanghai Institute of Organic Chemistry epoxidized 32 with high diastereoselectivity, then silylated the alcohol before opening the epoxide the anion 33 to give 34. When the addition was carried out on the free alcohol, the alternative regioisomer predominated (Chem. Asian J. 2017, 12, 2211. ).
D. F. Taber, Org. Chem. Highlights 2018, July 23.