C-O Ring Construction: Cephalasporolide F (Sartillo-Piscil), Hedycoropyran A (Kim/Lee), Applanatumol A (Ito), Lycibarbarine C (Liu/Du), Goniofufurone (Makabe), Angustatin A (Alcarazo)

Fernando Sartillo-Piscil of Benemérita Universidad Autónoma de Puebla previously reported an H-atom abstraction/fragmentation/cyclization cascade that converted 1 into the unstable spiroketal cephalosporolide F (2) that could only be observed in passing. He recently reported improved conditions based on photoredox catalysis that enabled the isolation of 2 (J. Org. Chem. 2015, 80, 2601, DOI: 10.1021/jo502757c; J. Org. Chem. 2023, 88, 4880, DOI: 10.1021/acs.joc.3c00251; 2015, November 16).

Hedycoropyran A (5) was isolated from the Asian herb Hedychium coronarium. Hyoungsu Kim and Dongjoo Lee of Ajou University assembled 5 via the diastereoselective oxidative cyclization of 3 to 4 (J. Org. Chem. 2023, 88, 17172. DOI: 10.1021/acs.joc.3c02046). For an alternative approach to 5, see 2018, January 15).

Applanatumol A (8) was isolated from Ganodema applanatum, a medicinal mushroom that has been used to treat chronic renal disease. Hisanaka Ito of the Tokyo University of Pharmacy and Life Sciences devised a route to 8 based on the intramolecular oxy-Michael cyclization of 6 to 7 (Chem. Commun. 2023, 59, 8139. DOI: 10.1039/D3CC01997G).

Lycibarbarine C (11) was isolated from the berries of Lycium barbarum (goji berries, wolfberries), used as a tonic in traditional Chinese medicine. Jun Liu and Yuguo Du of the Research Center for Eco-Environmental Sciences of the Chinese Academy of Sciences devised the sequential acid-catalyzed transformation of the acetonide 9 to 10 and then to 11 (Eur. J. Org. Chem. 2023, 26, e202300518. DOI: 10.1002/ejoc.202300518). Arun K. Ghosh of Purdue University reported a complementary approach (J. Org. Chem. 2023, 88, 9530. DOI: 10.1021/acs.joc.3c00749).

Goniofufurone (14), isolated from the southeast Asian tree Goniothalamus giganteus, showed anti-proliferative activity against HL-60 cells. Hidefumi Makabe of Shinshu University assembled 14 by the Pd-mediated carbonylation of the iodoalkene 12 to 13, that cyclized to 14 under the reaction conditions (Tetrahedron Lett. 2023, 132, 154827. DOI: 10.1016/j.tetlet.2023.154827).

The cyclophane angustatin A (17) was isolated from the liverwort Asterella angusta. Manuel Alcarazo of the Georg-August-Universität Gottingen constructed 17 by the macrocyclization of the aldehyde 15 to 16, followed by phenanthrene construction (Org. Lett. 2023, 25, 7181. DOI: 10.1021/acs.orglett.3c02742).