Partner und Internationale Organisationen
(Englisch)
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A, B, HR, CZ, DK, F, D, H, IRL, I, LV, NL, N, PL, P, RO, SI, E, S, CH, GB
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Abstract
(Englisch)
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A network consisting of five groups (F, UK, IT, CH) has been launched aiming at developing new types of desymmetrization reactions and applying them for total synthesis. In this network, our role it to develop radical based desymmetrization reactions. In 2001, our work has concentrated on two topics: 1) A radical annulation procedure based on a highly stereoselective conjugated addition of a cyclic 1-hydroxyacid derivative to methyl acrylate followed by a fully group selective cyclization has been developed. The 1,3-stereoinduction during the cyclization step is the only component of this process that is not fully controlled. The reaction furnished only two out of the 16 possible diastereomers. This reaction opens a new approach for the preparation of polysubstituted 1-hydroxycyclopentane carboxylic acid derivatives. 2) A one-pot procedure for the conversion of carboxylic acids into homoallylic alcohols under remarkably mild and selective conditions has been described. The triethylammonium salts of alkanoic acids are treated with Bu3P/PhSeCl to afford the corresponding acyl selenides that are reduced by tributyltin hydride under radical conditions to aldehydes. Direct in situ trapping of the aldehydes by allylboronates affords the desired homoallylic alcohols. Preparation of optically active alcohols by use of a tartrate modified allylboronate is possible and the enantioselectivities are similar to the one obtained when isolated aldehydes are employed.
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