Herein we have found a second example of doubly enantiophobic behavior during the crystallization of rac-1-benzyl-3-chloro-4-[(4-chlorophenyl)sulfanyl]-5-hydroxy-1,5-dihydro-2H-pyrrol-2-one, i.e., the formation of two conglomerates with different crystal structures in the absence of any racemic compounds. In both polymorphic modifications, the main supramolecular motif is appeared to be a hydrogen-bonded chain or helix of different symmetry, which is related to an α-hydroxyamide chain synthon. Additional crosslinking of the homochiral chains in the crystals of both crystalline forms, which is realized through weak, noncovalent interactions, can be a probable reason for the reproducibility and stability of the α-hydroxyamide chain synthon and polymorphic diversity registered. It was shown that each of the conglomerates is thermodynamically stable in certain temperature ranges. For the first time, a binary phase diagram for the chiral system complicated by an enantiotropic phase transition is reconstructed based on experimental data, which is characterized by the presence of a thermodynamic stability permutation line between the two racemic conglomerates.

Methods for the synthesis of novel optically active bisthioethers and disulfones of the furan-2(5H)-one series were developed. Bisthioethers with the dithiol fragment links two γ-lactone rings at the C⁴ atoms were synthesized by the reaction of 5(S)-(l-menthyloxy)- and 5(S)-(l-bornyloxy)furan-2(5H)-ones with ethane-1,2-dithiol and propane-1,3-dithiol in the presence of triethylamine. Chiral disulfones with a monoterpene alcohol fragment in the 5 position of the γ-lactone ring were obtained by the oxidation of the dithio furanone derivatives with hydrogen peroxide in acetic acid. The structure of five novel sulfur-containing furanone derivatives was characterized by single crystal X-ray diffraction.

Two crystalline diastereomorphs of rac-1-benzyl-3-bromo-5-hydroxy-4-[(4-methylphenyl)sulfanyl]-1,5-dihydro-2Н-pyrrole-2-one are obtained and characterized: the racemic compound (P2₁/c) and the normal conglomerate (P6₅, P6₁). The conglomerate is shown to be more thermodynamically preferred while the racemic compound is a metastable form in the entire temperature range studied. These two modifications are formed as a mixture during routine crystallization from a solution and characterized by a similar density, however, their structures significantly differ in the parameters of hydrogen bonds. A small difference in the free energies of two phases at room temperature, which is found by differential scanning calorimetry, explains the experimental availability of both forms during crystallization from the solution. The formation of a stronger hydrogen bond in the conglomerate crystals, which is detected by X-ray diffraction and solid-state vibrational spectroscopy, may be explained by a more favorable arrangement of donor and acceptor groups of the neighboring molecules in a homochiral helix of the conglomerate as compared with a heterochiral dimer, which is the main motif in crystals of the racemic compound.