C-O Ring Construction: The Rizzacasa Synthesis of Trachyspic Acid 19-n-Butyl Ester

Márcio W. Paixão of the Federal University of São Carlos and Burkhard König of the Universität Regensburg assembled 3 by coupling 1 with 2 (Adv. Synth. Catal. 2020, 362, 2367. DOI: 10.1002/adsc.202000167). Alexander J. Grenning of the University of Florida prepared the tetrahydrofuran 5 by the thermolysis of 4 (Org. Lett. 2020, 22, 842. DOI: 10.1021/acs.orglett.9b04306). Delong Liu of Shanghai Jiao Tong University coupled 6 with 7, leading to the dihydrofuran 8 (Org. Lett. 2020, 22, 4680. DOI: 10.1021/acs.orglett.0c01483). Mykhaylo A. Potopnyk and Sławomir Jarosz of the Polish Academy of Sciences warmed 9 to give an intermediate, to which they added 10, to give 11 (J. Org. Chem. 2020, 85, 3517. DOI: 10.1021/acs.joc.9b03247).

Hirokazu Tsukamoto of the Yokohama University of Science developed the reductive cyclization of 12 to the tetrahydropyran 13 (Adv. Synth. Catal. 2019, 361, 3733. DOI: 10.1002/adsc.201900450). Xing-Wang Wang of Soochow University, Yuanzhi Xia of Wenzhou University and Zheng Wang of the Shanghai Institute of Organic Chemistry devised the enantioselective hetero Diels-Alder combination of 14 with 15, leading to the dihydropyran 16 (ACS Catal. 2020, 10, 3556. DOI: 10.1021/acscatal.9b05606). Can Zhu, Fahmi Himo and Jan-E. Bäckvall of Stockholm University coupled 17 with 18 to give 19 (J. Am. Chem. Soc. 2020, 142, 5751. DOI: 10.1021/jacs.9b13700). Frank Hahn of the Universität Bayreuth achieved high diastereoselectivity in the enzymatic cyclization of 20 to 21 (ACS Catal. 2020, 10, 4973. DOI: 10.1021/acscatal.9b05071).

Chaorong Qi of the South China University of Technology used 22 to promote the cyclo-oligomerization of 1, leading to 23 (Chem. Commun. 2020, 56, 6495. DOI: 10.1039/D0CC00135J). Iris Antes of the Technical University Munich and Franz Bracher of Ludwig-Maximilians University Munich prepared the macrocycle 25 by the intramolecular Pictet-Spengler cyclization of 24 (Org. Biomol. Chem. 2020, 18, 3047. DOI: 10.1039/D0OB00078G). Hirosato Takikawa of the University of Tokyo observed high diastereoselectivity in the thermal rearrangement of 26 to 27 (Tetrahedron Lett. 2020, 61, 151825. DOI: 10.1016/j.tetlet.2020.151825). Satoshi Ichikawa of Hokkaido University optimized the reductive cyclization of 28 to 29 (Org. Lett. 2020, 22, 2697. DOI: 10.1021/acs.orglett.0c00665).

Trachyspic acid 19-n-butyl ester (32), isolated from the fungus RKGS-F2684, is a selective inhibitor of polo-like kinase 1. Mark A. Rizzacasa of the University of Melbourne assembled 31 by the acid cyclization of 30 followed by ozonolysis and β-elimination (Org. Lett. 2020, 22, 1972. DOI: 10.1021/acs.orglett.0c00319).