Diastereoselective Ring-Closing Metathesis in the Synthesis of Dihydropyrans
摘要:
An investigation into the factors influencing the diastereochemical outcome of the ring-closing metathesis based synthesis of dihydropyrans is presented in this paper. Divinyl carbinols derived from alpha-hydroxy carboxylic acid esters are elaborated to trienes with two diastereotopic vinyl moieties. Depending on the steric demand of the oxo substituent of the divinyl carbinol moiety (either unprotected OH, TBDMS, or benzyl ether) different diastereomers are preferrably formed upon ring-closing metathesis. An extension to diastereoselective double ring-closing metathesis in the formation of spirocycles has also been investigated.
presence of lithiumdialkylamides to functionalized 2,3-dihydropyrans or 2,3-dihydrofurans, respectively, is described. The regiochemical outcome of the reaction can be influenced by the relative configuration of the starting epoxides and the steric demand of the base. The 2,3-dihydropyrans obtained were converted stereoselectively to difunctionalized 3,4-dihydropyrans by the carbon-Ferrier reaction, or to
Synthesis of Functionalized 2,3- and 3,4-Dihydropyrans Starting from α-Hydroxycarboxylic Esters <i>via</i> RCM
作者:Bernd Schmidt、Holger Wildemann
DOI:10.1055/s-1999-2884
日期:——
α-Hydroxy carboxylic acids and their derivatives are naturally occurring starting materials for the synthesis of functionalized tetrahydropyrans using ring closing metathesis and base induced epoxide rearrangement as key steps. (S)-Lactic acid methyl ester has been used as the starting material for the preparation of enantiomerically pure 6-desoxy C-glycoside precursors.