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The title compound, [Ni(C13H11N4S2)2], was obtained by the reaction of S-2-picolyldi-thio-carbazate and pyridine-2-carbaldehyde with nickel(II) acetate. The Ni(II) atom is located on a twofold rotation axis and is bonded to four N atoms at distances of 2.037 (8) and 2.109 (9) Å, and to two S atoms at a distance of 2.406 (3) Å, leading to a distorted octa-hedral coordination. The angle between the mean planes of the coordinating moieties of the two symmetry-related tridentate ligands is 83.3 (2)°. In the crystal, complex mol-ecules are linked by weak C-H⋯S hydrogen bonds, π-π inter-actions between the pyridine rings [centroid-centroid distance = 3.775 (9) Å] and C-H⋯π inter-actions. The hydrogen-bonding inter-actions lead to the formation of layers parallel to (010); π-π inter-actions link these layers into a three-dimensional network.

X-ray crystallographic analysis with Cu Kα radiation established the relative configurations of the stereogenic centers in the title compound, C(15)H(20)N(2)O(5), and clarified mechanistic ambiguities in the synthesis. The conformation of the five-membered ring approximates twisted, about a C-O bond. The absolute configuration of this carbon-branched dipeptide isostere was known based on the use of d-ribose as the starting material. Refinement of the Flack parameter gave an ambiguous result but the refined Hooft parameter is in agreement with the assumed (d-ribose) absolute structure. The crystal structure consists of N-H⋯O and O-H⋯O hydrogen-bonded bi-layers, with the terminal methyl and phenyl groups forming a hydro-phobic inter-layer inter-face. Some weak C-H⋯O inter-actions are also present.

The title compound, C(21)H(26)O(10)S, was synthesized in a single step from mannose penta-acetate. The mol-ecular structure confirms the α configuration of the anomeric thioaryl substituent. Spectroscopic and melting-point data obtained for the title compound are in disagreement with those previously reported, indicating the previously reported synthesis [Durette & Shen (1980 ▶). Carbohydr. Res. 81, 261-274] to be erroneous. The crystal structure is stabilized by weak inter-molecular C-H⋯O hydrogen bonds.

The Kiliani reaction on 1-de-oxy-(N,N-dimethyl-amino)-d-fructose, itself readily available from reaction of dimethyl-amine and d-glucose, proceeded to give access to the title β-sugar amino acid, C(15)H(27)NO(7). X-ray crystallography determined the stereochemistry at the newly formed chiral center. There are two mol-ecules in the asymmetric unit; they are related by a pseudo-twofold rotation axis and have very similar geometries, differing only in the conformation of one of the acetonide rings. All the acetonide rings adopt envelope conformations; the flap atom is oxygen in three of the rings, but carbon in one of them. There are two strong hydrogen bonds between the two independent mol-ecules, and further weak hydrogen bonds link the mol-ecules to form infinite chains running parallel to the a axis.

The title compound, C(40)H(31)NO(11)S·0.53CH(2)Cl(2)·0.38C(4)H(10)O, was synthesized in two steps from mannose penta-acetate and single crystals were grown by slow evaporation. The structure was determined by single-crystal X-ray diffraction, confirming the α-configuration of the anomeric thioaryl substituent. The asymmetric unit contains two crystallographically distinct mol-ecules of the carbohydrate. The central pyran-ose rings of these are geometrically similar, but there are differences in the orientations of the benzoate substituents.