Application of Mn(III)-catalysed olefin hydration reaction to the selective functionalisation of avermectin B 1

• Published in: Tetrahedron letters Vol. 51; no. 13; pp. 1706 - 1709
• Main Authors: Cassayre, Jérôme, Winkler, Tammo, Pitterna, Thomas, Quaranta, Laura
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 31.03.2010; Elsevier
• Subjects: Abamectin; Acaricide; Avermectin; Chemistry; Chemistry, Organic; Emamectin; Hydration; Insecticide; Mn(III); Natural product; Physical Sciences; Science & Technology; Abamectin; Acaricide; Insecticide; Hydration; Natural product; Emamectin; Avermectin; Mn(III); DIOXYGEN; ALPHA,BETA-UNSATURATED KETONES; CONVERSION; (+/-)-KOPSIDASINE-N-OXIDE; PHENYLSILANE; REDUCTION; MN-III CATALYST; ESTERS; MOLECULAR-OXYGEN
• ISSN: 0040-4039; 1873-3581
• DOI: 10.1016/j.tetlet.2010.01.080

New avermectin derivatives were prepared by Mn(III)-catalysed hydration reaction of different substrates. The Mn(dpm) 3-catalysed olefin hydration reaction of α,β-unsaturated esters and ketones discovered by Mukaiyama in 1990 and further developed by Magnus in 2000 was applied to the challenging environment of avermectin B 1. Different avermectin substrates such as 4″,7-OTMS-5-oxo-avermectin B 1 3, avermectin B 1 1 and Δ 2,3-avermectin B 1 6 were thus treated with Mn(dpm) 3, PhSiH 3 in isopropanol under oxygen atmosphere to afford several novel analogues, including 3,4-dihydro-3-hydroxy-avermectin B 1 8 with high level of regio- and stereoselectivity, 2-hydroxy-3,4-dihydro-avermectin B 1 7, the first example of a 2-substituted avermectin and the novel 22,23-dihydro-22-hydroxy-avermectin B 1 9a and 9b, epimeric at C(22). Biological activity of these new avermectin derivatives is also reported.