- Epoxide hydrolase Lsd19 for polyether formation in the biosynthesis of lasalocid A: Direct experimental evidence on polyene-polyepoxide hypothesis in polyether biosynthesis
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Polyether metabolites are an important class of natural products. Although their biosynthesis, especially construction of polyether skeletons, attracted organic chemists for many years, no experimental data on the enzymatic polyether formation has been obtained. In this study, a putative epoxide hydrolase gene lsd19 found on the biosynthetic gene cluster of an ionophore polyether lasalocid was cloned and successfully overexpressed in Escherichia coli. Using the purified Lsd19, a proposed substrate, bisepoxyprelasalocid, and its synthesized analogue were successfully converted into lasalocid A and its derivative via a 6-endo-tet cyclization mode. On the other hand, treatment of the bisepoxide with trichloroacetic acid gave isolasalocid A via a 5-exo-tet cyclization mode. Therefore, the enzymatic conversion observed in this study unambiguously showed that the bisepoxyprelasalocid is an intermediate of the lasalocid biosynthesis and that Lsd19 catalyzes the sequential cyclic ether formations involving an energetically disfavored 6-endo-tet cyclization. This is the first example of the enzymatic epoxide-opening reactions leading to a polyether natural product. Copyright
- Shichijo, Yoshihiro,Migita, Akira,Oguri, Hiroki,Watanabe, Mami,Tokiwano, Tetsuo,Watanabe, Kenji,Oikawa, Hideaki
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supporting information; body text
p. 12230 - 12231
(2009/02/05)
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- Stereoselective Total Synthesis of Polyether Ionophore Antibiotics, Isolasalocid A and Lasalocid A. Part 2. The Total Synthesis via Stereoselective Construction of the B Rings by Chelation-Controlled Cyclization under Thermodynamic Conditions
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Stereoselective total synthesis of isolasalocid A (1) and lasalocid A (2) was achieved via construction of the tetrahydrofuran rings by chelation-controlled cyclization of the corresponding p-methoxyphenyl substituted allyl alcohols (6, 7) under thermodyn
- Horita, Kiyoshi,Noda, Ichio,Tanaka, Kazuhiro,Oikawa, Yuji,Yonemitsu, Osamu
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p. 5997 - 6018
(2007/10/02)
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- Stereoselective synthesis of polyether antibiotics, lasalocid A and isolasalocid A, via a chelation-controlled formation of tetrahydrofuran rings under thermodynamic conditions
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The B-rings (2,5-trans-tetrahydrofurans) of lasalocid A (6) and isolasalocid A (7) were stereoselectively constructed from the corresponding p-methoxyphenylallyl alcohols (13a, 13b) by treatment with ZnBr2 to give C13-C24 fragments (14a, 14b) via a new chelation-controlled cyclization under thermodynamic conditions. After their conversion into lasalocid ketone (19) and BOM-isolasalocid ketone (20), coupling with the C1-C11 aldehyde (22) completed the synthesis of 6 and 7, respectively.
- Noda,Horita,Oikawa,Yonemitsu
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p. 6035 - 6038
(2007/10/02)
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