**3. Results and Discussion**

Six structures of fagopyrins A–F (Scheme 1) proposed by Benkovi´c et al. [17] were optimized in the gas phase. Conformational analysis was performed for the A–F structures by searching for the minimum on local potential energy surfaces.

**Scheme 1.** Analyzed structures of (**a**) fagopyrin A, (**b**) fagopyrin B, (**c**) fagopyrin C, (**d**) fagopyrin D, (**e**) fagopyrin E, and (**f**) fagopyrin F.

Conformers representing different arrangements and interactions of substituent hydroxyl groups, carbonyl oxygen, piperidine, and pyrrolidine rings were compiled based on a structure with minimum energy. The close position of the substituents allowed for the formation of intramolecular interactions at the "peri" (O-H···O···H-O) and "bay" region of the molecules (O-H···O-H). Additionally, the presence of piperidine and pyrrolidine substituents allowed for the formation of new interactions with the nitrogen atom.
