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124 results on '"CERRINI, S."'

27. Structure-activity relationships in the ansamycins. Molecular structure and activity of 3-carbomethoxy rifamycin S.

Author

Brufani, M, Cellai, L, Cerrini, S, Fedeli, W, Segre, A, and Vaciago, A

Abstract

The X-ray and NMR structural study of 3-carbomethoxy rifamycin S5 was undertaken in order to determine whether its low antimicrobial activity was related to a conformation of the molecule which was unfavorable for interaction with bacterial DNA-dependent RNA polymerase. However, the molecule assumes a conformation similar to that of the active rifamycins. Indeed the compound was found to be active on the isolated enzyme, so that its low activity on whole bacteria has to be attributed to factors affecting its penetration through the bacterial cell wall.

Published
1982

29. A study of structure-activity relationships in 4-deoxypyrido[1',2'-1,2]imidazo[5,4-c]rifamycin SV derivatives by electron spectroscopy for chemical analysis and 1H NMR.

Author

Cellai, L, Cerrini, S, Segre, A, Battistoni, C, Cossu, G, Mattogno, G, Brufani, M, and Marchi, E

Abstract

A new class of rifamycins, 4-deoxypyrido[1',2'-1,2]imidazo[5,4-c]rifamycin SV derivatives, has been synthesized. They are potent antibacterial agents and are not absorbed at the gastrointestinal level and can therefore probably be used as antibacterial intestinal disinfectants. From the present X-ray, electron spectroscopy for chemical analysis, and 1H NMR study, it appears that this peculiar pharmacokinetic behavior is mainly to be attributed to the fact that the pyridoimidazo system exists in these compounds in a mesomeric betaine form, bearing one positively and one negatively charged nitrogen. If it is assumed that rifamycins are generally absorbed by passive diffusion, the presence of the two oppositely charged nitrogens, together with the presence of the phenolic hydroxyls, means that these molecules are ionized at all pH values encountered along the gastrointestinal tract, which thus prevents their absorption. These molecules also display a strong tendency to self-associate both in solution and in the solid state, and the increase in molecular size may also play a role in preventing their absorption.

Published
1985

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