Metal-Mediated Carbocyclic Construction: The Xu Synthesis of Astellatol
Christopher Uyeda of Purdue University developed Simmons-Smith conditions that were selective for the less substituted of two alkenes, enabling the conversion of 1 to 2 (Chem. Sci. 2018, 9, 1604. ). Yohei Okada of the Tokyo University of Agriculture and Technology devised a photocatalytic protocol for the 2+2 cycloaddition of 3 to 4 to give cyclobutane 5 (J. Org. Chem. 2018, 83, 4948. ).
Jieping Zhu of the Ecole Polytechnique Fédérale de Lausanne arylated the prochiral cyclopentene 6 with the diazonium salt 7, leading to 8 in high ee (Angew. Chem. Int. Ed. 2018, 57, 2721. ). Fayang G. Qiu and Yehua Jin of Launch-Pharma Technologies effected the ring contraction of 9, available in kilogram quantities from carvone, to the ester 10 (Org. Process Res. Dev. 2018, 22, 377. ). Tushar Kanti Chakraborty of the Indian Institute of Science, Bengaluru cyclized 11 with high diastereocontrol to 12 (J. Org. Chem. 2018, 83, 6086. ). Robert A. Fowlers II of Lehigh University and Andreas Gansäuer of the Universität Bonn developed a more efficient protocol for such cyclizations (Chem. Eur. J. 2018, 24, 6371. ). Song Lin of Cornell University added the activated cyclopropane 13 to the diene 14, leading to the ketone 15 in high ee (J. Am. Chem. Soc. 2018, 140, 3514. ). Eric Meggers of Philipps-Universität Marburg described related results (Angew. Chem. Int. Ed. 2018, 57, 5454. ).
Yannick Landais of the University of Bordeaux established conditions for the selective reductive alkylation of the biphenyl 16 with 17 to give 18 (Heterocycles 2018, 97, 459. ). David Sarlah of the University of Illinois opened the adduct between benzene 19 and the dienophile 20 with the Grignard reagent 21, leading to the product 22 in high ee (J. Am. Chem. Soc. 2018, 140, 4503. ). Nobuharu Iwasawa of the Tokyo Institute of Technology cyclized the propargyl ether 23 to the alkyne 24 (J. Am. Chem. Soc. 2018, 140, 7769. ). Mark Lautens of the University of Toronto assembled the cyclohexanol 27 by combining the diketone 25 with the alkyne 26 (Org. Lett. 2018, 20, 1380. ).
Masahito Murai and Kazuhiko Takai of Okayama University inserted the alkyne 29 into the β-keto ester 28 to give the cyclooctenone 30 (ACS Catal. 2018, 8, 5454. ). Glenn C. Micalizio of Dartmouth College combined the alkyne 31 with the alkyne 32 to give the angularly substituted trans fused 6/5 C/D steroidal chiron 33 (Nature Chem. 2018, 10, 70. ).
The pentacyclic sesterterpenoid astellatol 36 was isolated from Aspergillus stellatus (syn. A. variecolor). Jing Xu of the Southern University of Science and Technology installed the four-membered ring of 36 by the SmI2-mediated cyclization of 34 to 35 (Angew. Chem. Int. Ed. 2018, 57, 3386. ).