NEW SUPRAMOLECULAR HOST SYSTEMS .2. 1,3,5,7-TETRAOXADECALIN, 1,2-DIMETHOXYETHANE AND THE GAUCHE EFFECT REAPPRAISED - THEORY VS EXPERIMENT

The three 1,3,5,7-tetraoxadecalin diastereomers (1, 2 & 3), core moiet ies of new host and macromolecular systems, were calculated ''ab initi o'' and analysed in terms of their fragment-components, C-O-C-O-C and C-O-C-C-O-C with their stereoelectronic effects, namely the ''anomeric effect'' and ''gauche effect'', respectively. The inadequacy of split valence basis sets and of molecular mechanics (MM2, MM3) calculations (in reproducing relative stability and structural parameters) was res olved by using high level basis sets and electron correlation. The ori gins and consequences of the ''gauche effect'' were critically discuss ed and reparametrization of MM3 force field for C-O-C-C-O-C containing systems, provided a reliable computational tool for the target cis-1, 3,5,7-tetraoxadecalin system and other O-C-C-O containing systems.