Molecular mechanics (CONFLEX/MM3) search/minimization study of the conformations of ornoside and escuside

The conformations of a secoiridoid glucoside (ornoside, 1) and a coumarine-secoiridoid (escuside, 2) were studied with the MM3 force field. The CONFLEX conformational search procedure was used for finding low-energy conformations. The computed data of I indicate an equilibrium between several hydrogen bonded conformations with prevailing folded conformations of the macroring endocyclic dihedrals. The conformational preference of 2 is biased towards two conformations that differ only in the rotations about bonds adjacent to the ester function. The present results provide insight into the most probable conformations of ornoside and escuside and compliment earlier NMR studies. (c) 2005 Elsevier B.V. All rights reserved.