Reduction: The Suh Synthesis of Dendroside C Aglycon

Albert Poater of the Universitat de Girona and Jean-Luc Renaud of Normandie University devised an iron catalyst for the selective reduction of the cyclohexenone 1 to the cyclohexanone 2 (Chem. Eur. J. 2018, 24, 5770. DOI: 10.1002/chem.201800995). Karol Grela of the Polish Academy of Sciences showed that a Ru metathesis catalyst reduced 3 to 4 with remarkable selectivity (J. Org. Chem. 2018, 83, 2542. DOI: 10.1021/acs.joc.7b02468). Rylan J. Lundgren of the University of Alberta prepared the Z-alkene 6 by the selective reduction of 5 (Angew. Chem. Int. Ed. 2018, 57, 3981. DOI: 10.1002/anie.201800361). Martin Goetz of the Martin-Luther-Universität Halle-Wittenberg found that under LED irradiation, ascorbate and a Ru catalyst could reduce the α,β-unsaturated compound 7 to 8 (Angew. Chem. Int. Ed. 2018, 57, 1078. DOI: 10.1002/anie.201711692).

Bernhard Breit of the Albert-Ludwigs Universität Freiburg established conditions for the reduction of the carboxylic acid 9 to the hydrocarbon 10 (ACS Catal. 2018, 8, 785. DOI: 10.1021/acscatal.7b03484). Ji Lu of the Southwest Medical University and Zhenlei Song of Sichuan University used the silane 12 to reduce the ketone 11 directly to 13. Note that both silyl ethers and isolated alkenes (not illustrated) were stable (Chem. Commun. 2018, 54, 4834. DOI: 10.1039/C8CC01163J). Yoshiaki Nakao of Kyoto University prepared 15 by removing the nitro group from 14 (Org. Lett. 2018, 20, 1655. DOI: 10.1021/acs.orglett.8b00430). Zhong-Xia Wang of the University of Science and Technology of China removed the pyridyloxy group from 16, leading to 17. This is particularly noteworthy because it was the pyridyloxy group that directed the catalytic ortho arylation to prepare 16 (Chem. Commun. 2018, 54, 2138. DOI: 10.1039/C7CC09668B).

Duk Keun An of Kangwon National University devised a reagent for the selective reduction of the amide 18 to the aldehyde 19 (Tetrahedron Lett. 2018, 59, 2335. DOI: 10.1016/j.tetlet.2018.04.082). Lu Gao Zhenlei Song, also of Sichuan University, reported related results (J. Org. Chem. 2018, 83, 1687. DOI: 10.1021/acs.joc.7b02868). Sabuj Kundu of the Indian Insitute of Technology Kanpur used methanol to convert the nitrile 20 to the amine 21 (ACS Catal. 2018, 8, 2890. DOI: 10.1021/acscatal.8b00021). Meike Niggemann of RWTH Aachen University showed that 23 could be prepared by the electrophilic amination of an organozinc with the intermediate from partial reduction of the nitroalkane 22 (Chem. Eur. J. 2018, 24, 3970. DOI: 10.1002/chem.201705986). Michel R. Gagné of the University of North Carolina selectively reduced just one of the three carbonyls in converting 24 to 25 (Chem. Commun. 2018, 54, 5855. DOI: 10.1039/C8CC01863D).

The sesquiterpene dendroside C was isolated from the Japanese orchid Dendrobium moniliforme. En route to the aglycon (28), Young-Ger Suh of Seoul National University reduced the enol phosphate 26 to the alkene 27 (Org. Lett. 2018, 20, 586. DOI: 10.1021/acs.orglett.7b03701).