Studies on the stereoselective selenolactonization, hydroxy and methoxy selenenylation of α- and β-hydroxy acids and esters. Synthesis of δ- and γ-lactones |
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Authors: | Carmela AprileMichelangelo Gruttadauria Maria E AmatoFrancesca D'Anna Paolo Lo MeoSerena Riela Renato Noto |
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Institution: | a Dipartimento di Chimica Organica ‘E. Paternò’, Viale delle Scienze, Parco d'Orleans II, 90128 Palermo, Italy b Dipartimento di Scienze Chimiche, Viale A. Doria 6, 95125 Catania, Italy |
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Abstract: | The diastereoselective synthesis of hydroxy substituted γ- and δ-lactones was accomplished following two approaches. A 5- or 6-endo cyclization promoted by electrophilic selenium reagents of α- or β-hydroxy acids and a 5- or 6-exo cyclization of hydroxy esters obtained through a diastereoselective hydroxy selenenylation reaction of α- or β-hydroxy esters. Moreover, the diastereoselective methoxy selenenylation of the above compounds was investigated showing a case in which the compound that was unreactive in the hydroxy selenenylation conditions gave, in the methoxy selenenylation conditions, the deprotected diol. The usefulness of the methoxy selenenylation procedure was proven by the preparation of a symmetric compound unsymmetrically functionalized. Yields and selectivities were found to depend on substituents (Ph or alkyl groups at the carbon atom that undergoes the nucleophilic attack), mode of cyclization, kinetic or thermodynamic control conditions. In the latter case, silica gel played an important role. |
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Keywords: | cyclization diols lactones selenium and compounds |
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