Oxidation: The Hong/Gui Synthesis of Bufospirostenin A
Oleg V. Larionov of the University of Texas at San Antonio devised a protocol for the decarboxylative coupling of an acid 1 with an arenesulfinate 2 to give the sulfoxide 3 (Angew. Chem. Int. Ed. 2022, 61, e202210525. DOI: 10.1002/anie.202210525). Xiaotian Qi and Aiwen Lei of Wuhan University effected the coupling of the alkene 4 with the amine 5, leading to the allylic amine 6 (Nature Catal. 2022, 5, 642. DOI: 10.1038/s41929-022-00818-y). Jun Luo, Bing-Cheng Hu, and Chao Jiang of the Nanjing University of Science and Technology oxidized the oxime ether 7 to the nitrate ester 8, that could be reduced to the diol or amine, or directly converted to the corresponding azide (Org. Biomol. Chem. 2023, 21, 75. DOI: 10.1039/D2OB01919A). Shyam Sathyamoorthi of the University of Kansas cyclized the sulfamate 9 to the allylic amine 10 (Tetrahedron 2022, 128, 133112. DOI: 10.1016/j.tet.2022.133112).
Zhenbo Gao of Nanjing Agricultural University developed mild conditions for the selective oxidation of an allylic alcohol 11 to the enone 12 (Tetrahedron Lett. 2022, 103, 153976. DOI: 10.1016/j.tetlet.2022.153976). John C.-G. Zhao, also of the University of Texas at San Antonio, effected the α-acyloxylation of the ketone 13 to the ester 14 (Chem. Commun. 2022, 58, 11308. DOI: 10.1039/D2CC04016F). Sebastian Stecko of the Polish Academy of Sciences observed high regioselectivity in the Wacker oxidation of the allylic amine 15 to the ketone 16 (Org. Biomol. Chem. 2023, 21, 115. DOI: 10.1039/D2OB01843H). Marco Simonetti of the University of Manchester and Daniele Leonori of RWTH Aachen University devised a practical protocol for the nitroarene-mediated cleavage of the alkene 17 to the aldehyde 18 (Nature 2022, 610, 81. DOI: 10.1038/s41586-022-05211-0). Marvin Parasram of New York University described in more detail the historical background of this cleavage (J. Am. Chem. Soc. 2022, 144, 15437. DOI: 10.1021/jacs.2c05648).
Maciej Giedyk, also of the Polish Academy of Sciences, reported the oxidation of the amide 19 to the acid 20 (Eur. J. Org. Chem. 2022, e202200913. DOI: 10.1002/ejoc.202200913). Rene M. Koenigs, also of RWTH Aachen University, and Jun Xuan of Anhui University assembled the amide 23 by the triazolium salt-catalyzed coupling of the aldehyde 21 and the diazo ester 22 with nitrosobenzene (ACS Catal. 2022, 12, 11129. DOI: 10.1021/acscatal.2c02875). Yu Yuan of Yangzhou University used sodium nitrite to oxidize the methyl pyridine 24 to the nitrile 25 (Org. Lett. 2022, 24, 6341. DOI: 10.1021/acs.orglett.2c02596). John A. Porco Jr. and Feng Yang of Boston University employed Sc(OTf)3 to promote the Baeyer-Villiger conversion of the ketone 26 to the lactone 27 (J. Am. Chem. Soc. 2022, 144, 12970. DOI: 10.1021/jacs.2c05366).
Bufospirostenin A (30), isolated from the bile of the toad Asiatic toad Bufo gargarizans, is a potent inhibitor of Na/K ATPase. In the course of a synthesis of 30, Xin Hong of Zhejiang University and Jinghan Gui of the Shanghai Institute of Organic Chemistry effected the oxidative cleavage of the tertiary alcohol 28 to the medium ring ketone 29 (J. Am. Chem. Soc. 2022, 144, 17769. DOI: 10.1021/jacs.2c07944).