Reduction: The Xu Synthesis of Himalensine A
Zhuangzhi Shi of Nanjing University showed that 1 could be semireduced to 2, with the deuteriums being delivered from the relatively inexpensive D2O (Chem. Commun. 2019, 55, 6922. DOI: 10.1039/C9CC03213D). Jinfei Yang and Fei Sun of Nantong University developed a protocol for reducing the alkyne 3 selectively to the E alkene 4 (Chem. Commun. 2019, 55, 1903. DOI: 10.1039/C8CC09714C). Huiying Zeng of Lanzhou University and Chao-Jun Li of McGill University used isopropyl alcohol to reduce 5 to 6 (Chem. Commun. 2019, 55, 767. DOI: 10.1039/C8CC08942F). Johannes F. Teichert of the Technische Universitšt Berlin found that under Cu catalysis, deuterium gas could reduce 7 regioselectively to 8 (Chem. Eur. J. 2019, 25, 985. DOI: 10.1002/chem.201805530).
Martin Oestreich, also of the Technische Universitšt Berlin, effected the net decarbonylation of 9 to 10 (Chem. Eur. J. 2019, 25, 8508. DOI: 10.1002/chem.201902082). Xin Hong of Zhejiang University and Michal Szostak Rutgers University/Newark used a Pd catalyst to decarboxylate 11 to 12 (Chem. Sci. 2019, 10, 5736. DOI: 10.1039/C9SC00892F). Chi Wai Cheung and Jun-An Ma of Tianjin University prepared the amide 15 by reducing 13 in the presence of 14 (Org. Chem. Front. 2019, 6, 756. DOI: 10.1039/C8QO01405A). Robin J. Prince, Fang Gao and Brian T. Hopkins of Biogen showed that the product from partial reduction of 16 could engage in reductive amination with 17, leading to 18 (J. Org. Chem. 2019, 84, 7936. DOI: 10.1021/acs.joc.9b00816).
Johannes G. de Vries of the Leibniz Institute for Catalysis, Rostock demonstrated that ethanol in the presence of an iron catalyst could reduce the ester 19 to the alcohol 20 (Angew. Chem. Int. Ed. 2019, 58, 1129. DOI: 10.1002/anie.201810605). Michael Findlater of Texas Tech University described related work (Org. Biomol. Chem. 2019, 17, 1834. DOI: 10.1039/C8OB02661K). Jin Xie, also of Nanjing University, reduced the acid 21 to the deuterated aldehyde 22 (Angew. Chem. Int. Ed. 2019, 58, 312. DOI: 10.1002/anie.201811522). Patrick H. Toy of the University of Hong Kong showed that it was possible to reduce the diene 23 selectively to the ketone 24 (Synlett 2019, 30, 1100. DOI: 10.1055/s-0037-1611537). Xiaoji Wang of the Jiangxi Science and Technology Normal University and Shuangping Huang of the Taiyun University of Technology devised conditions, including the use of N-acetylcysteine (26), for the reduction of the epoxy ketone 25 to the β-hydroxy ketone 27 (Synlett 2019, 30, 748. DOI: 10.1055/s-0037-1612215).
Himalensine A (30) is a pentacyclic Daphniphyllum alkaloid isolated from the Himalayan evergreen Daphniphyllum himalense. In the course of a synthesis of 30, Jing Xu of the Southern University of Science and Technology used the Kabalka protocol to stereoselectively reduce 28 to 29, setting the stage for the intramolecular Heck cyclization that followed (Angew. Chem. Int. Ed. 2019, 58, 7390. DOI: 10.1002/anie.201902908).