Functional Group Protection: The Renaud Synthesis of Brefeldin C

Richmond Sarpong of the University of California, Berkeley reduced the epoxide 1 to the enone 2 (J. Org. Chem. 2019, 84, 12209. DOI: 10.1021/acs.joc.9b01937). E. J. Corey of Harvard University showed that an alkyl aryl sulfide 3 could be converted to the iodide 4 (Tetrahedron Lett. 1968, 9, 5787. DOI: 10.1016/S0040-4039(00)76351-9).

Mohammad Al-Masum of Tennessee State University found that a Pd catalyst promoted the esterification of 5 with 6 to give 7 (Tetrahedron Lett. 2019, 60, 150936. DOI: 10.1016/j.tetlet.2019.07.027). Kazutada Ikeuchi of Hokkaido University and Hidetoshi Yamada of Kwansei Gakuin University demonstrated that the secondary 4-methyl benzyl ether of 8 could be selectively removed, leading to 9 (Org. Lett. 2019, 21, 6638. DOI: 10.1021/acs.orglett.9b02144). Richard R. Schmidt of the University of Konstanz and Jian-Song Sun of Jiangxi Normal University used Zn to deprotect 10 to 11 (Org. Lett. 2019, 21, 8049. DOI: 10.1021/acs.orglett.9b03025). Jürgen Klankermayer of RWTH Aachen University assembled 13 by coupling 12 with CO₂ (Chem. Eur. J. 2019, 25, 11412. DOI: 10.1002/chem.201901660).

Kazuya Yamaguchi of the University of Tokyo oxidized the amine 14 selectively to the formamide 15 (Angew. Chem. Int. Ed. 2019, 58, 16651. DOI: 10.1002/anie.201909005). Ainara Nova of the University of Oslo and Matthias Beller of the Leibniz-Institut für Katalyse e.V. an der Universität Rostock observed that the formamide of 16 could be selectively deprotected, leading to 17 (Chem. Sci. 2019, 10, 10566. DOI: 10.1039/C9SC03453F). Patrick S. Fier and Kevin M. Maloney of Merck Process established conditions for the removal of the mesyl group from 18, leading after protection to 19 (J. Am. Chem. Soc. 2019, 141, 18416. DOI: 10.1021/jacs.9b10985). Hun Young Kim and Kyungsoo Oh of Chung-Ang University used an o-naphthoquinone to oxidize 20 selectively to 21 (ACS Catal. 2019, 9, 9216. DOI: 10.1021/acscatal.9b03442).

Stephen L. Buchwald of MIT converted the oxazole 22 to the nitrile 23 (J. Am. Chem. Soc. 2019, 141, 18668. DOI: 10.1021/jacs.9b10875). Yu Du and Qiang Kang of the Fujian Institute of Resarch on the Structure of Matter saponified the isoxazole 24 to the carboxylic acid, leading after esterification to 25 (Org. Chem. Front. 2019, 6, 2775. DOI: 10.1039/C9QO00676A).

A heterocycle can be used to protect more than one functional group. In the course of a synthesis of brefeldin C (28), Philippe Renaud of the University of Bern oxidised the furan 26 to the keto aldehyde 27 (Chem. Eur. J. 2019, 25, 11646. DOI: 10.1002/chem.201903392).