Bacteriostatic action of streptomycin on ribosomally resistant mutants (rpsL) of Salmonella typhimurium.

Incubation of streptomycin-resistant (rpsL) mutants of Salmonella typhimurium in alkaline nutrient medium containing streptomycin brought about an inhibition of cell growth that was readily reversed by removing the antibiotic or neutralizing the medium. Growth inhibition was maximal at pH 8.2 and a streptomycin concentration of 800 micrograms/ml. A similar amount of dihydrostreptomycin had a negligible effect, and 10-times-higher concentrations of this antibiotic were required to reproduce the streptomycin action. Addition of streptomycin (400 micrograms/ml) to rpsL cells in alkaline (pH 8.2) nutrient medium caused inhibition of protein and DNA synthesis and also, but to a lower degree, of RNA synthesis. This effect on macromolecular synthesis was not due to ATP deprivation, since ATP content rose after addition of the antibiotic. At pH 8.2, the rate of entrance of streptomycin increased fourfold with respect to the rate at pH 7.0, leading to a large accumulation of streptomycin into rpsL cells. Uptake of the antibiotic was halted by addition of KCN or chloramphenicol. Equal uptake was obtained with 800 micrograms of dihydrostreptomycin or 400 micrograms of streptomycin per ml, yet the former did not affect cell growth at that concentration. It is concluded that high pH stimulates streptomycin and dihydrostreptomycin uptake by rpsL strains but only streptomycin accumulation causes growth inhibition in cells lacking the high-affinity ribosomal site.

Aminoglycoside antibiotics. 7. Dihydrostreptomycin analogues.

Dihydrostreptomycin analogues with structural variations in their guanidino groups were prepared. The analogue with a methyl group on the guanidine at C-1 was nearly as active as dihydrostreptomycin against bacteria. However, the 2-imidazolin-2-ylamino substituent at C-1 eliminated activity. No analogue with a substituent on the C-3 guanidino group was active.

A synthesis of dihydrostreptomycin.

A key protected streptidine derivative (3) useful for the synthesis of antibiotics of streptomycin series was prepared by hydrolysis of an acylated dihydrostreptomycin (DHSM) derivative (2), and it was condensed with a protected dihydrostreptobiosaminyl chloride (5) to give two condensation products (6 and 7). By deblocking, 6 was led to DHSM and 7 to a biologically inactive isomer (8) of DHSM. From the PMR spectrum of 4-O-mesyl derivative (4) of 3, the benzyloxycarbonyl and acetyl groups were concluded to be attached to the end nitrogens of the guanidine groups.

1- and 3-deamidino derivatives of dihydrostreptomycin and some 1-N-acyl derivatives.

1-Deamidino-, 3-deamidino- and 1,3-di(deamidino)dihydrostreptomycin (1, 2, 3) were prepared by treatment of dihydrostreptomycin (DHSM) with ammonia at 100 degrees C. The 3-guanidino group of DHSM is suggested to be more important than the 1-guanidino group for the antibacterial activity of DHSM. 1-N-[(S)-4-Amino-2-hydroxybutyryl) and 1-N-[(S)-4-guanidino-2-hydroxybutyryl] derivatives (4, 6) of 1-deamidinodihydrostreptomycin were futher prepared.