STRUCTURE AND CONFORMATION OF HETEROCYCLES .25. NEW SUPRAMOLECULAR HOST SYSTEMS .1. A STRUCTURAL AND CONFORMATIONAL STUDY OF THE 1,3,5,7-TETRAOXADECALIN CORE SYSTEM

This is the first in a series of studies of new host systems based on the 1,3,5,7-tetraoxadecalin (TOD) core moiety. The parent molecule (2) and its 2,6-di(trans-styryl) derivative (5) were studied in the cryst al (low temperature X-ray diffraction, electron density, geometry) and in solution (static and dynamic NMR). The relative energies from the solution studies and the structural parameters from the X-ray analysis were compared with those from a ring-fragment analysis and with struc tural data of 1,3-dioxanes and 1,3,5,7-tetraoxadecalins which were ret rieved from the Cambridge Structural Database. Molecular mechanics cal culations using MM2 and MM3 performed poorly in reproducing relative e nergies and structural parameters. This is attributed to stereoelectro nics in the 1,3,5,7-TOD system.