
%0 Journal Article
%A Clark-Lewis, JW 
%A Jemison, RW 
%A Nair, V 
%T Flavan derivatives. XXIV. <I>cis</I>- and <I>trans</I>-3-Methoxyflavanones
%J Australian Journal of Chemistry
%D 1968/12/01
%V 21
%N 12
%P 3015-3024
%K 
%R https://doi.org/10.1071/CH9683015
%U https://www.publish.csiro.au/paper/CH9683015 
%X Oxidation of three 2,3-cia-3,4-cis-3-methoxyflavan-4-ols with active manganese dioxide gave the corresponding 2,3-cis-3-methoxyflavanones which were equilibrated in deuterochloroform containing trifluoroacetic acid to mixtures of cis- (c.33%) and trans-3-methoxyflavanones (c.67%). Tominaga's base-catalysed cyclization of 2'-hydroxy-&#945;-methoxycha1cones to 3-methoxyflavanones has been found to yield the 2,3-trans isomers. The higher stability of the 2,3-trans-configuration of 3-hydroxy-   flavanones (dihydroflavonols) compared with 3-methoxyflavanones is attributed to hydrogen bonding; no cis-isomer was detected when acid-catalysed epimerization of a trans-3-hydroxyflavanone was attempted. M.m.r. data are reported for the compounds described. 
