Construction of Alkylated Centers: The Zu Synthesis of Aflatoxin B2
Jialin Wen and Xumu Zhang of the Southern University of Science and Technology hydrogenated 1 to 2 in high ee (Org. Chem. Front. 2019, 6, 1438. DOI: 10.1039/C8QO01291A). Guohua Hou of Beijing Normal University reported related results (J. Am. Chem. Soc. 2019, 141, 1749. DOI: 10.1021/jacs.8b12657). T. V. RajanBabu of Ohio State University described the preparation of 4 by the enantioselective hydroboration of 3 (J. Am. Chem. Soc. 2019, 141, 7365. DOI: 10.1021/jacs.8b13812). Robert Kourist of the Graz University of Technology engineered an enzyme that decarboxylated 5, leading to 6 (Chem. Eur. J. 2019, 25, 5071. DOI: 10.1002/chem.201806339). Scott J. Miller of Yale University devised a phosphothreonine-based peptide that catalyzed the enantioselective Baeyer-Villiger oxidation of 7 to 8 (ACS Catal. 2019, 9, 242. DOI: 10.1021/acscatal.8b04132).
Yuichi Kobayashi of the Tokyo Institute of Technology demonstrated that the pyridylsulfonate 9 could be displaced by the Grignard reagent 10, leading to 11 with clean inversion (Org. Lett. 2019, 21, 3247. DOI: 10.1021/acs.orglett.9b00976). Shaolin Zhu of Nanjing University showed that under Ni catalysis, the internal alkene of 13 could be isomerized and coupled with the racemic bromide 12, to give 14 (Angew. Chem. Int. Ed. 2019, 58, 1754. DOI: 10.1002/anie.201813222). David W. Lupton of Monash University assembled 17 by using an N-heterocyclic carbene catalyst to couple 15 with 16 (Angew. Chem. Int. Ed. 2019, 58, 4007. DOI: 10.1002/anie.201812585). Bing-Feng Shi of Zhejiang University achieved high selectivity in the insertion of 19 into just one of the thirteen C-H's of 18, leading to 20 in high ee (J. Am. Chem. Soc. 2019, 141, 4558. DOI: 10.1021/jacs.9b01124).
Several methods have been put forward for the asymmetric assembly of quaternary alkyated centers. Takuya Kanemitsu and Takashi Itoh of Showa University used a Cinchona-derived phase transfer catalyst to mediate the Michael addition of 21 to 22 to give 23 (Tetrahedron 2019, 75, 209. DOI: 10.1016/j.tet.2018.11.037). Eric Meggers of the Philipps-Universitšt Marburg described the catalytic electrochemical coupling of 24 with 25, to give 26 (Nature Catal. 2019, 2, 34. DOI: 10.1038/s41929-018-0198-y). Bi-Jie Li of Tsinghua University prepared 29 by adding 28 to the alkene of 27 (J. Am. Chem. Soc. 2019, 141, 9312. DOI: 10.1021/jacs.9b03027). Liang-Qiu Lu and Wen-Jing Xiao of Central China Normal University used a Pd catalyst to add 30 to 31, leading to an intermediate that rearranged to 32 (J. Am. Chem. Soc. 2019, 141, 133. DOI: 10.1021/jacs.8b12095).
The aflatoxins, including aflatoxin B2 (36), are produced by Aspergillus flavus and Aspergillus parsiticus, fungi that are found on agricultural crops such as maize and peanuts. To set the absolute configuration of 36, Liansuo Zu, also of Tsinghua University, used a Hayashi-JÝrgensen proline-derived catalyst to mediate the direct addition of the nucleophilic arene 33 to 34, leading to 35 (Chem. Commun. 2019, 55, 5171. DOI: 10.1039/C9CC01833F).