Oxidation: The Sherman/Williams Synthesis of Baulamycin A

Zhankui Sun of Shanghai Jiao Tong University devised photolytic conditions for the oxidation of the acid 1 to the alcohol 2 (J. Org. Chem. 2020, 85, 5019. DOI: 10.1021/acs.joc.0c00312). Kazunori Nagao and Hirohisa Ohmiya of Kanazawa University also used photolysis to prepare the tert-butyl ether 5 by coupling the ester 3 with the alcohol 4 (J. Am. Chem. Soc. 2020, 142, 1211. DOI: 10.1021/jacs.9b12335). Oleg V. Larionov of the University of Texas at San Antionio alkylated the amine 6 with the acid 7, leading to the amine 8 (Angew. Chem. Int. Ed. 2020, 59, 7921. DOI: 10.1002/anie.201916710). Bing Han of Lanzhou University found that the peranhydride 9 could be converted directly to the borate ester 10 (Org. Lett. 2020, 22, 234. DOI: 10.1021/acs.orglett.9b04218).

Alexander O. Terent’ev of the N. D. Zelinsky Institute of Organic Chemistry assembled 13 by coupling 11 with 12 under oxidative conditions (J. Org. Chem. 2020, 85, 1935. DOI: 10.1021/acs.joc.9b02656). Diwan S. Rawat of the University of Delhi demonstrated that triflic acid effectively catalyzed the IBX oxidation of the alcohol 14 to the ketone 15 (Tetrahedron Lett. 2020, 61, 151749. DOI: 10.1016/j.tetlet.2020.151749). Matthias Beller of the Leibniz-Institute for Catalysis and Paul J. Dyson of the École Polytechnique Fedérale de Lausanne devised a Co catalyst that directly mediated the dehydrogenative cross-coupling of the amine 16 with the amine 17, leading to the imine 18 (Angew. Chem. Int. Ed. 2020, 59, 7501. DOI: 10.1002/anie.201915526). Ohyun Kwon of UCLA effected the oxidative cleavage of the alkene 19 to the ketone 20 (Angew. Chem. Int. Ed. 2020, 59, 1211. DOI: 10.1002/anie.201913201).

Jianbo Wang of Peking University oxidized the tertiary alcohol 21 to the bromo ketone 22 (Chem. Commun. 2020, 56, 5002. DOI: 10.1039/D0CC01720E). Zhong-Quan Liu of the Nanjing University of Chinese Medicine reported related results (ACS Catal. 2020, 10, 6603. DOI: 10.1021/acscatal.0c01495). Kevin Lam of the University of Greenwich devised a general route to ortho esters such as 24, based on the electrochemical oxidation of the corresponding dithiane 23 (Org. Lett. 2020, 22, 4000. DOI: 10.1021/acs.orglett.0c01324). Timothy W. Funk of Gettysburg College demonstrated the selective oxidation of the diol 25 to the lactone 26 (J. Org. Chem. 2020, 85, 1823. DOI: 10.1021/acs.joc.9b01884).

Ming Wang and Xuefeng Jiang of East China Normal University assembled the sulfone 29 by the three-component coupling of the ester 27, the bromide 28 and sodium dithionite (Angew. Chem. Int. Ed. 2020, 59, 8907. DOI: 10.1002/anie.202001589). Under Ramberg-Bäcklund conditions, such a sulfone can readily be converted to the corresponding alkene.

The new antibiotic baulamycin A (32) was isolated in low yield from Streptomyces tempisquensis. In the course of a synthesis of 32, David H. Sherman of the University of Michigan and (the late) Robert M. Williams of Colorado State University used ozone on silica gel to convert the phenyl group of 30 to the carboxylic acid of 31 (J. Org. Chem. 2020, 85, 3812. DOI: 10.1021/acs.joc.9b03443).