Functional Group Protection: The Reisman Synthesis of Perseanol
Jan Streuff of the Albert-Ludwigs-Universitšt Freiburg developed conditions to remove the alkene-containing alkyl group from 1, leading to 2 (ACS Catal. 2020, 10, 6409. DOI: 10.1021/acscatal.0c01605). Dayong Sang and Juan Tian of the Jinchu University of Technology prepared the salicylaldehyde (4) by selectively demethylating 3 (J. Org. Chem. 2020, 85, 6429. DOI: 10.1021/acs.joc.0c00290). Akihiko Tsuda of Kobe University devised a protocol for the in situ production of phosgene, enabling the assembly of the carbonate 6 by the coupling of the alcohol 5 with phenol (Org. Lett. 2020, 22, 3566. DOI: 10.1021/acs.orglett.0c01013). William P. Gallagher of Bristol-Meyers Squibb observed high regioselectivity in the conversion of the acetal 7 to the vinyl ether 8 (Tetrahedron Lett. 2020, 61, 151750. DOI: 10.1016/j.tetlet.2020.151750).
Scott D. Taylor of the University of Waterloo used the chloride 10 in conjunction with silver nitrate to protect the amine 9 as the 9-phenyl-9-fluorenyl Weinreb amide 11 (J. Org. Chem. 2020, 85, 2068. DOI: 10.1021/acs.joc.9b02809). Carlos del Pozo of the University of Valencia introduced the vinyl sulfonamide protecting group, deprotecting 12 with ozone, followed by reprotection to give 13 (Chem. Commun. 2020, 56, 1425. DOI: 10.1039/C9CC09113K). Mitsuru Shindo of Kyushu University oxidized the benzyl amine 14 with DMSO, leading to the aniline 15 and the aldehyde 16 (Chem. Lett. 2020, 49, 191. DOI: 10.1246/cl.190854). Liang Wang and Shubai Li of the Changzhou Vocational Institute of Engineering effected the photooxidation of the oxamic acid 17 to give an activated intermediate, that was trapped with benzylamine 18 to give the unsymmetrical urea 19 (Tetrahedron Lett. 2020, 61, 151962. DOI: 10.1016/j.tetlet.2020.151962).
Chin-Fa Lee of the National Chung Hsing University showed that the protection of the aldehyde 20 with 21 to give 22 could be promoted photochemically (Eur. J. Org. Chem. 2020, 2542. DOI: 10.1002/ejoc.202000218). Conversely, Xingang Xie of Lanzhou University found that the same conditions, except under air, led to the deprotection of the oxathiolane 22 to 20 (Org. Biomol. Chem. 2020, 18, 288. DOI: 10.1039/C9OB02517K). Ramakrishna G. Bhat of the Indian Institute of Science Education and Research used the same conditions to deprotect dithianes (Tetrahedron Lett. 2020, 61, 151407. DOI: 10.1016/j.tetlet.2019.151407).
Paul J. Hergenrother of the University of Illinois established that diazomethane could be generated in situ from 24, to convert the acid 23 to the methyl ester 25 (Angew. Chem. Int. Ed. 2020, 59, 1857. DOI: 10.1002/anie.201911896). Neil K. Garg of UCLA showed that 27 in the presence of a Ni catalyst could deprotect the tertiary amide 26, leading to 28 with the ee maintained (Org. Lett. 2020, 22, 2833. DOI: 10.1021/acs.orglett.0c00885).
In the course of a synthesis of perseanol (31), Sarah Reisman of Caltech observed that the oxidation of the allylic alcohol 29 with excess dimethyldioxirane gave not just the desired enone, but also deprotected the benzylidene acetal, leading to 30 with significant regioselectivity (Nature 2019, 573, 563. DOI: 10.1038/s41586-019-1580-x).