Potassium salts of hypodiphospho­ric acid

Structural analysis of six potassium salts of hypodiphospho­ric acid, H₄P₂O₆, containing the anions in all possible basicities, is focused on the anion structure and the organization of the anionic and cationic sublattices.

A 1:1 cocrystal of baicalein with nicotinamide

Cocrystallization of baicalein with nicotinamide yields a 1:1 cocrystal [systematic name: pyridine-3-carboxamide-5,6,7-trihy­droxy-2-phenyl-4H-chromen-4-one (1/1)], C₆H₆N₂O·C₁₅H₁₀O₅. The asymmetric unit contains one baicalein and one nicotinamide mol­ecule, both in neutral forms. Mol­ecules in the cocrystal form column motifs stabilized by an array of inter­molecular hydrogen bonds.

The first 3':5'-cyclic nucleotide-amino acid complex: L-His-cIMP

In the crystal structure of the L-His-cIMP complex, i.e. L-histidinium inosine 3':5'-cyclic phosphate [systematic name: 5-(2-amino-2-carb­oxy­eth­yl)-1H-imidazol-3-ium 7-hy­droxy-2-oxo-6-(6-oxo-6,9-dihydro-1H-purin-9-yl)-4a,6,7,7a-tetra­hydro-4H-1,3,5,2[lambda]⁵-furo[3,2-d][1,3,2[lambda]⁵]dioxaphosphinin-2-olate], C₆H₁₀N₃O₂⁺·C₁₀H₁₀N₄O₇P^-, the Hoogsteen edge of the hypo­xanthine (Hyp) base of cIMP and the Hyp face are engaged in specific amino acid-nucleotide (His...cIMP) recognition, i.e. by abutting edge-to-edge and by [pi]-[pi] stacking, respectively. The Watson-Crick edge of Hyp and the cIMP phosphate group play a role in nonspecific His...cIMP contacts. The inter­actions between the cIMP anions (anti/C3'-endo/trans-gauche/chair conformers) are realized mainly between riboses and phosphate groups. The results for this L-His-cIMP complex, compared with those for the previously reported solvated L-His-IMP crystal structure, indicate a different nature of amino acid-nucleotide recognition and inter­actions upon the 3':5'-cyclization of the nucleotide phosphate group.