Structure and conformation of heterocycles. 13. conformational analysis of 2,3-DI(R)OXY-1,4-dioxanes: anomeric and gauche effects

A series of trans- and cis-2,3-di R)oxy-1,4-dIoxanes (R = Me,Ph, Ac) and some 2,5-disubstituted analogis were prepared and analysed by various NMR techniques. The trans isomers occur in more than 96% as diaxial conformers. Molecular mechanics calculations largely confirm these findings, which are interpreted -in terms of combined anomeric and gauche effects.