A new cocrystal salt of metformin, an antidiabetic drug, and N,N’-(1,4-phenylene)dioxalamic acid, was synthesized by mechanochemical synthesis, purified by crystallization from solution and characterized by single X-ray crystallography. The structure revealed a salt-type cocrystal composed of one dicationic metformin unit, two monoanionic units of the acid and four water molecules namely H2Mf(HpOXA)2∙4H2O. X-ray powder, IR, 13C-CPMAS, thermal and BET adsorption-desorption analyses were performed to elucidate the structure of the molecular and supramolecurar structure of the anhydrous microcrystalline mesoporous solid H2Mf(HpOXA)2. The results suggest that their structures, conformation and hydrogen bonding schemes are very similar between them. To the best of our knowledge, the selective formation of the monoanion HpOXA⁻, as well as its structure in the solid, is herein reported for the first time. Regular O(-)∙∙∙C(), O(-)∙∙∙N+ and bifacial O(-)∙∙∙C()∙∙∙O(-) of n→* charge-assisted interactions are herein described in H2MfA cocrystal salts which could be responsible of the interactions of metformin in biologic systems. The results, support the participation of n→* charge-assisted interactions independently, and not just as a short contact imposed by the geometric constraint due to the hydrogen bonding patterns.

Background: Boronic acids form di-ester bonds with cis-hydroxyl groups in carbohydrates. The formation of these adducts could impair the physical and chemical properties of the precursors, even their biological activity. Methods: Two carbohydrate-derivatives from D-fructose and D-arabinose and phenylboronic acid were synthesized in a straightforward one-step procedure and chemically characterized by spectroscopy and X-ray diffraction crystallography. Also, an acute toxicity test was performed to determine their Lethal Dose50 (LD50) by using the Lorke’s method. Results: Analytical chemistry assays confirmed adducts by the generation of the diester bonds with a β-D-pyranose of carbohydrates, including signals corresponding to the formation of new bonds, like the stretching of B-O bonds. The NMR spectra yielded information about the stereoselectivity in the synthesis reaction by the finding of just one signal in the range for the anomeric carbon in the 13C NMR spectra of both adducts. The acute toxicity tests showed that LD50 value for both compounds is 1265 mg/kg, while Effective Dose 50 for sedation is 531 mg/kg. However, differences were in the onset and lapse of sedation. Conclusions: These adducts are bioactive and highly safe agents. Further biological evaluation is desirable to explore medical purposes.