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The crystal structure of y sulphanilamide has been determined from Patterson and heavy atom electrondensity projections on the (100) plane, and by the heavy atom method for the three-dimensional refinement.The parameters were refined by least-squares applied to 876 independent reflexions. The final R index was 0.10. The bonded distances and angles are comparable to those in ~ and B sulphanilamide. The hydrogen bond system is discussed.

A sodium complex of monensin B isolated and purified by chromatography has crystallized as a monohydrate (Mon B)Na.H20, C35H59NaOII.H20, M r = 696.8. The cell is orthorhombic, space group P2~212 r with a = 12.135(1), b = 14.976(2), c = 20.683 (1)A, V= 3758.8A 3, Z = 4, D x = 1.23 Mgm -3, F(000) = 1580. The structure has been refined to R = 0.029 (for 107 atoms) for 2349 observed reflexions. The heterocyclic part of the anion wraps the cation which is coordinated to six O atoms; two hydrogen bonds between the carboxylate group of one end and the two hydroxyl groups of the other end close the anionic ring. This conformation is very similar to that already known for complexes of monensin A. The water molecule is hydrogen bonded to two anions in a new mode compared to the cell organization of the other complexes.

The 1:2 magnesium ion complex of the antibiotic calcimycine (A. 23187) crystallizes in the space group P21, with cell dimensions a = 11.152(2), b = 27.684(2), c = 10.168(2) Å, β = 107.02(2)°, and Z = 2. The structure was refined to an R = 0.063 based on 3473 observed reflections. The octahedral coordination of the Mg2+ ion is highly symmetrical. Each calcimycine ion is bound to Mg2+ through a carboxyl oxygen, a carbonyl oxygen, and the nitrogen of the benzoxazole ring system. The Mg—O distances are respectively 2.00 Å and 2.06 Å, the Mg—N distances 2.23 Å [Formula: see text].

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