Whereas simple 4,4Ј-bi(1,3-dioxanyl)s 16 and 19 displayed little conformational preference at the inter-ring bond, their derivatives 4 and 13, with equatorial methyl groups in the 5and 5Ј-positions, each showed a strong conformational preference to populate a conformation with a gauche arrangement of the oxygen atoms. These results form the basis of a
To relate material properties or biological functions of a flexible compound to structure Ϫ that is, to constitution Ϫ an understanding of the number and nature of low-energy conformations available to such a molecule is essential. In this context, we are interested in learning what modification of flexible alkane chains gives them the property that they populate predominantly one single conformation, or put another way, that they adopt a distinct shape despite maintaining flexibility. The key is to destabilize all the undesired backbone conformations related to the one desired conformation by suitable placement of substituents. A conceivable starting point for such an undertaking is represented by alkane chains bearing a single substituent at each of their secondary carbon atoms, such as 2,3,4,5-tetramethylhexane. We reported recently on the conformational analysis of meso-2,3,4,5-tetramethylhexane and of some of its derivatives. The , isomer 1 should posess a distinctly different conformational behaviour. We elaborate here on how compounds with strong conformational preferences may be attained by structural modification of ,-2,3,4,5tetramethylhexane.