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Stereospecific synthesis of 1,6-dioxadecalins and 2,2'-linked ditetrahydrofurans by rearrangement of steroidal spiroacetals
|Authors:||Betancor, Carmen; Dorta, Rosa L.; Freire, Raimundo CSIC; Martín, Ángeles CSIC ORCID ; Prangé, Thierry; Suárez, Ernesto CSIC ORCID||Issue Date:||7-Aug-1998||Publisher:||American Chemical Society||Citation:||Journal of Organic Chemistry 63(18): 6355-6362 (1998)||Abstract:||The reduction of steroidal spiroacetal methanesulfonate derivatives, containing the 1,6-dioxaspiro[4.5]decan-10-yl ring system, with DIBALH promotes a new rearrangement to give steroidal 1,6-dioxadecalin (octahydropyrano[3,2-b]pyran) or 2,2‘-linked ditetrahydrofuran (octahydro[2,2‘]bifuranyl) derivatives. To study the scope and selectivity of the reaction, several steroidal spiroacetals such as (23R,25R)-3β-methoxy-5α-spirostan-23-yl methanesulfonate (2) and its 23S-isomer (5) and (22R,23R,25R)-3β-acetoxy-16β,23:23,26-diepoxycholest-5-en-22-yl methanesulfonate (15) and its 22S-isomer (19) have been synthesized. Compound 2 was rearranged with absolute regio- and stereoselectivity to give (22S,23S,25R)-3β-methoxy-16β,23:22,26-diepoxy-5α-cholestane (3) which possesses a cis-fused 1,6-dioxadecalin ring system. The reaction of compound 5 gave exclusively (22S,23R,25R)-3β-methoxy-23,26-epoxy-5α-furostane (6) in which the spiroacetal was converted into a ditetrahydrofuran subunit. The two other isomeric spiroacetals 15 and 19 were also mainly transformed into (22S,23S,25R)-3β-acetoxy-16β,23:22,26-diepoxycholest-5-ene (16) and (22R,23R,25R)-3β-acetoxy-23,26-epoxyfurost-5-ene (20), respectively. A mechanism is proposed to explain the regio- and sterospecificity observed in the rearrangement.||Description:||8 pages, 1 figure, 5 schemes.-- PMID: 11672270 [PubMed].-- Printed version published Sep 4, 1998.
Supporting information available at: http://pubs.acs.org/doi/suppl/10.1021/jo980834o
|Publisher version (URL):||http://dx.doi.org/10.1021/jo980834o||URI:||http://hdl.handle.net/10261/16967||DOI:||10.1021/jo980834o||ISSN:||0022-3263|
|Appears in Collections:||(IPNA) Artículos|
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