On the conformational varieties of 5-methoxy-N,N-dimethyltryptamine and serotonin in crystalline environment

On the conformational varieties of acetylcholine in the crystals of its halides

“…Examples of such situations have been reported by Perrin & Thozet (1974) for p-cresol. Altogether the conformation of acetylcholine in these various structures confirms the situation found in our previous studies on adrenaline (Caillet, Claverie & Pullman, 1976), serotonin and 5-methylated bufotenine (Caillet, Claverie & Pullman, 1977), namely that the requirement of minimizing the lattice energy overrides the requirement of minimizing the conformational energy, so that there is nothing surprising in the existence of different conformers in different crystal structures. The more difficult problem seems to be to understand the existence of these various lattice structures, rather than the conformational changes which appear as mere consequences of the changes of these structures.…”

“…The aim of this paper is to account for the effect of the crystalline environment on the conformation of acetylcholine. This work is thus a continuation of our previous studies on similar problems related to phenethylamines (Caillet, Claverie & Pullman, 1976) and indolalkylamines (Caillet, Claverie & Pullman, 1977). A priori, the present case appears especially delicate, since the conformational change of acetylcholine and the structural changes in the crystal occur merely by changing the co-crystallizing ion (CI-or Br-).…”

“…Hence it is necessary to represent these interactions as accurately as possible in order to elucidate the structural differences in which we are interested. The values used previously for CI- (Caillet, Claverie & Pullman, 1977) were obtained by a rough extrapolation from the parameters of the S atom, but no such simplification seemed possible for Br-. We therefore decided to reconsider the problem from a broader viewpoint.…”

New structure of serotonin salt – comparison and conformational analysis of all known serotonin complexes

“…The calculated conformational energy difference between creatinine sulfate and picrate is only about 2 kcal mol À1 , while the difference in lattice energy is 274 kcal mol À1 (Caillet et al, 1977). Exact values aside, it is important to note the magnitude of the difference in conformational and lattice energies.…”

On the polymorphism of barbituric acid derivatives

“…The method of computation of the crystal-lattice energy has been described (Caillet & Claverie, 1974, 1975Caillet, Claverie & Pullman, 1976, 1977, 1978a.…”