Functional Group Protection: The Meepowan Synthesis of Protoconstipatic Acid Methyl Ester

Liang Wang, Quan Zhang and Yue Chen of Nankai University effected transfer hydrogenation with dihydrotoluene 2 to selectively remove the benzyl group from 1, to give 3 (Angew. Chem. Int. Ed. 2023, 62, e202313186. DOI: 10.1002/anie.202313186). Bartholomäus Pieber of the Max-Planck-Institute of Colloids and Interfaces showed that visible light irradiation sufficed to remove the trityl ether from 4, leading to the alcohol 5 (Synthesis 2023, 55, 1367. DOI: 10.1055/a-1979-5933). Jimmie D. Weaver III of Oklahoma State University assembled the ether 8 via the visible light-promoted conversion of 7 to the trans cyclohexene, that coupled with the alcohol 6 (Org. Lett. 2023, 25, 7316. DOI: 10.1021/acs.orglett.3c02666). Armido Studer of the Universität Münster developed the silyl ether 9 that could be deprotected to the alcohol 10 by visible light (Chem. Sci. 2023, 14, 12615. DOI: 10.1039/D3SC04975B).

Nuno Maulide of the University of Vienna used a computational approach to design a new sulfonamide 13, from the amine 11 and the sulfonyl chloride 12, that is easily removed by a nucleophilic thiol (Chem. Eur. J. 2023, 29, e202301312. DOI: 10.1002/chem.202301312). Sabuj Kundu of the Indian Institute of Technology Kanpur showed that a Co catalyst mediated the hydrazine reduction of an azide 14 to the amine, that could be further protected as the pyrrole 16 (Adv. Synth. Catal. 2023, 365, 2959. DOI: 10.1002/adsc.202300556).

Ramu Sridhar Perali of the University of Hyderabad deprotected the thioglycoside 17 to the free lactol 18 by exposure to N-bromosuccinimide (Org. Biomol. Chem. 2023, 21, 5861. DOI: 10.1039/D3OB00922J). Sylvain Antoniotti of the Université Côte d’Azur developed an FeCl₃-catalyzed protocol for preparing the ketal 21 by the combination of the enone 19 with the diol 20 (Tetrahedron 2023, 149, 133734. DOI: 10.1016/j.tet.2023.133734). Shintaro Okumura and Yasuhiro Uozumi of the Institute for Molecular Science, Okazaki prepared the acid 23 by the visible-light promoted addition of CO₂ to the enone 22 (Org. Lett. 2023, 25, 5226. DOI: 10.1021/acs.orglett.3c01675). Yandong Zhang of Xiamen University converted the chloroalkene 24 to the enone 25 (J. Am. Chem. Soc. 2023, 145, 18642. DOI: 10.1021/jacs.3c06442).

Hee-Kwon Kim of Jeonbuk National University Medical School and Hospital showed that exposure of a t-butyl ester 26 to dichlorodiphenylmethane 27 converted it to the acid chloride 28 (J. Org. Chem. 2023, 88, 13291. DOI: 10.1021/acs.joc.3c01588). Paula L. Diaconescu of UCLA and Parisa Mehrkhodavandi of the University of British Columbia prepared the orthoester 31 by combining the lactone 29 with the epoxide 30 (ACS Catal. 2023, 13, 13195. DOI: 10.1021/acscatal.3c03450).

Protoconstipatic acid is the aglycone of a family of glycosides isolated, inter alia, from the coastal lichen Cladonia furcata, extracts of which kill leukemia cells in culture. Puttinan Meepowpan of Chiang Mai University assembled the methyl ester 35 from the diester 34, prepared by the combination of dimethyl itaconate 32 with anthracene 33 (Tetrahedron 2023, 145, 133620. DOI: 10.1016/j.tet.2023.133620).