Abstract
meso-Bicyclo[3.3.0]octane-3,7-dione mono ethylene ketal 1 has been converted into chiral enol derivatives with good enantioselectivity. In this paper we report the efficient stereoselective transformation of meso-bicyclo[3.3.0]octane-3,7-dione mono ethylene ketal into methyl 2-epielenolate 15, a direct precursor to the heteroyohimbine alkaloid tetrahydroalstonine. The synthetic work described shows that each ring of the bicyclic ketone can be functionalized independently with good regio- and stereo-control. A new procedure for installing the alkoxyacrylate function of mono-terpenoids is described and it has been shown that the cyclopentanone ring of methyl (1αH,6αH)-2α-methyl-8-oxo-3-oxabicyclo[4.3.0]non-4-ene-5--carboxylate 11 can be regiosalectively converted into enol derivatives which are cleaved to give D/E-ring precursors of Corynanthe alkaloids.
Published Version
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