C-O Ring Construction: The Liang Synthesis of Seconorrisolide B
Matthias Beller of the Leibniz Institute of Catalysis constructed the β-lactone 2 by carbonylation of the propargyl alcohol 1 (Angew. Chem. Int. Ed. 2020, 59, 21585. ). Corinna S. Schindler of the University of Michigan observed high diastereoselectivity in the preparation of the oxetane 5 by the photolytic addition of the α-keto ester 4 to the alkene 3 (Org. Lett. 2020, 22, 6516. ). Tehshik P. Yoon of the University of Wisconsin described a parallel study (Org. Lett. 2020, 22, 6520. ).
Yong-Min Liang of Lanzhou University also used photolysis to promote the cyclization of the allylic ether 6 to the iodide 7 (J. Org. Chem. 2020, 85, 9301. ). Arun K. Ghosh of Purdue University achieved high diastereoselectivity in the cyclization of the dihydrodioxepine 8 to the alcohol 9 (J. Org. Chem. 2020, 85, 10399. ).
Anna Brodzka and Ryszard Ostaszewski of the Polish Academy of Sciences assembled the δ-lactone 12 by ester exchange with 11 followed by ring-closing alkene metathesis (J. Org. Chem. 2020, 85, 15305. ). Professor Schindler and Danielle M. Schultz of Merck Process used a high-throughput approach to establish conditions for the Pd-mediated cyclization of 13 to the spirolactone 14 (J. Org. Chem. 2020, 85, 9071. ). Xiaoxiao Song and Qijian Ni of Anhui Normal University constructed the tetrahydropyran 17 by combining the monocarbonate 16 with the nitrile 15 (Org. Biomol. Chem. 2020, 18, 6617. ). Jacek Mlynarski of the Polish Academy of Sciences developed the hetero Diels-Alder addition of 18 to 19, leading to the dihydropyranone 20 in high ee (Eur. J. Org. Chem. 2020, 5388. ). Takashi Ooi of Nagoya University used a chiral borate to mediate the cyclization of the vinyl ether 21 to the dihydropyran 22 (Angew. Chem. Int. Ed. 2020, 59, 11456. ). Chang-Hua Ding of Shanghai University and Xue-Long Hou of the Shanghai Institute of Organic Chemistry coupled the cyclic carbonate 23 with the nitroalkene 24, leading to the tetrahydropyran 25 (Org. Lett. 2020, 22, 5375. ).
Fanyang Mo of Peking University prepared the macrolactone 27 by electrochemical oxidation of the β-hydroxy carboxylic acid 26 (Chem. Sci. 2020, 11, 12021. ). Yan-Kai Liu of the Ocean University of China used the Hayashi-Jørgensen organocatalyst to mediate the triply-convergent coupling of the nitroalkene 28, the unsaturated aldehyde 29 and N-Cbz hydroxylamine 30, leading to the bicyclic 31 (Chem. Commun. 2020, 56, 12765. ).
Seconorrisolide B (34) was isolated from a marine sponge, Dysidea sp., collected from the Red Sea. Guangxin Liang of ShanghaiTech University set the two sidechain stereocenters of 34 by the thermal extrusion of cyclopentadiene from 32, followed by diastereoselective intramolecular ene cyclization of the resulting unsaturated γ-lactone (Angew. Chem. Int. Ed. 2020, 59, 14111. ).