Sulfathiazole polymorphism studied by magic-angle spinning NMR.

The literature on sulfathiazole polymorphs has many confusions and inconsistencies. These are largely resolved by the distinctive appearance of (13)C magic-angle spinning NMR spectra, which immediately show the number of molecules in the crystallographic asymmetric unit. The spectra presented include those of a newly-recognized form. The assignments of the spectra are established and discussed in relation to such factors as electronic structure of the aromatic ring, second-order quadrupolar effects originating from the nitrogen nuclei, and hydrogen bonding. The results are compared to literature information on the crystal structures. When the amino group acts as a hydrogen bond acceptor, there is a shielding effect on C-4 to the extent of ca. 8 ppm (which should be compared to a further shielding by ca. 10 ppm for sulfathiazole sulfate). The fact that the spectrum of form III is similar to the sum of those of forms IV and V is rationalized in relation to the crystal structures. Some surprising variability of spectra with temperature and with specific sample is reported.

Assignments of solid-state 13C resonances for polymorphs of cortisone acetate using shielding tensor components.

Carbon-13 CP/MAS spectra have been obtained for seven polymorphic and solvated forms of cortisone acetate. For signals in the high-frequency region, the spinning sideband manifolds of the spectra recorded under slow-spinning conditions have been analysed to obtain the shielding tensor components for the five resonances at the highest frequency. These show characteristic values for given types of carbon and have enabled assignments of the C5 and C22 signals to be made with some certainty, providing firm evidence of cross-over between the shifts for these carbons between different polymorphs. Assignments are suggested more tentatively for the resonances from C3, C11 and C20. Comparison of chemical shifts for those forms with published X-ray structures enables conclusions to be drawn regarding hydrogen bonding in the remaining forms. Hydrogen bonding induces a high-frequency change in the isotropic chemical shift of approximately 3 ppm.

G1549, a new cyclic hydroxamic acid antibiotic, isolated from culture broth of Pseudomonas alcaligenes.

Antibiotic G1549, isolated from culture broth of Pseudomonas alcaligenes, is a new cyclic hydroxamic acid with a 1-hydroxy-2(1H)-pyridinone structure that complexes with metals. The structure of G1549 is suggested to be 1-hydroxy-5-methoxy-6-methyl-2(1H)-pyridinone. In vitro, G1549 and its copper and ferric complexes show moderate activity against Gram-positive bacteria, fungi and Trichomonas vaginalis. Topical application of G1549 and its copper and ferric complexes protect guinea pigs against cutaneous infection with Microsporum canis. The compounds, however, have some systemic toxicity in mice.

G1499-2, a new quinoline compound isolated from the fermentation broth of Cytophaga johnsonii.

A new quinoline compound, G1499-2[C18H21NO(I)] is produced by Cytophaga johnsonii. G1499-2 has an unusual structure containing a cyclopropylidene radical. The compound has limited antibiotic activity against a few bacteria. It is not toxic to mice.

G2201-C, a new cyclopentenedione antibiotic, isolated from the fermentation broth of Streptomyces cattleya.

Streptomyces cattleya produced a new cyclopentenedione antibiotic, G2201-C [C6H6O4(I)], which is moderatley active in vitro against Gram-positive bacteria, weakly active against Gram-negative bacteria, and inactive against fungi. G2201-C is toxic to mice.