Comparison of the conformation of floral odorants: a NMR and molecular dynamics study

Odorous molecules, cis- and trans-4-methylcyclohexyl tetrahydrofuran-2-yl or pyranyl ethers, have been studied from the points of view of conformation and dynamics with the aim of extracting information on the relationships between white flower odour and structure. Both NMR and molecular dynamics analyses showed that cis derivatives, endowed with a main white flower note, have a bent structure corresponding to an oval molecular shape; the trans derivatives, exhibiting different odours, possess an extended structure corresponding to a cylindrical molecular shape. This comparison was also applied to two aromatic ethers both with a main floral note, 4-tert-butylphenyl tetrahydropyran-2-yl ether and 4-isopropylphenyl tetrahydrofuran-2-yl ether. These molecules also have similar conformations. All conformations for all molecules are independent of the solvent used, CDCl3 or 2H6DMSO (NMR) or vacuum, CHCl3 or DMSO (molecular dynamics).