Chemistry of the Neomycins. XII1 The Absolute Configuration of Deoxystreptamine in the Neomycins, Paromomycins and Kanamycins

Biosynthesis of 2-deoxystreptamine-containing aminoglycoside antibiotics

The 2-deoxystreptamine-containing aminoglycosides are an important class of clinically valuable antibiotics. A deep understanding of the biosynthesis of these natural products is required to enable efforts to rationally manipulate and engineer the biological production of novel aminoglycosides. This review discusses the development of our biosynthetic knowledge over the past half-century, with emphasis on the relatively recent contributions of molecular biology to the elucidation of these biosynthetic pathways.

An investigation of site-selective gas-phase reactions of amino alcohols with dimethyl ether ions

The reactions of dimethyl ether ions with neutral amino alcohols were examined in both a quadrupole ion trap mass spectrometer and a triple quadrupole mass spectrometer. These ion-molecule reactions produced two types of ions: the protonated species [M+l](+) and a more complex product at [M+13](+). The abundance of the [M+13](+) ions relative to that of the [M+1](+) ions decreases with increasing formal interfunctional distance. Multistage collision-activated dissociation techniques were used to characterize the [M+13](+) product ions, their reactivities, and the mechanisms for their formation and dissociation. In addition, molecular semiempirical calculation methods were used to probe the thermochemistry of these reactions. Reaction at the amino alcohol nitrogen site is favored, and the resulting [M+13](+) addition products may cyclize for additional stabilization. Comparisons were made among the behavior of related compounds, such as alcohols, diols, amines, and diamines. The alcohols reacted only to form the protonated species, but the diols, amines, and diamines all formed significant amounts of [M+13](+) ions or related dissociation products.

Identification of dekamycin antibiotics

Dekamycin was isolated from strain DK5 of Streptomyces fradiae, and purified by ion-exchange column chromatography. Excellent separation of N-acetylated derivatives of the antibiotic mixture was achieved by two different methods, flash chromatography and high-performance liquid chromatography. Mass spectrometry (252Cf plasma desorption mass spectrometry, fast atom bombardment) for the analysis of N-acetyldekamycins (neomycin B, neomycin C, neamine and ribostamycin) was mainly used to confirm the molecular weight of a structure deduced by 1H and 13C NMR analyses.

Chemical modification of neamine

The aminocyclitol antibiotic neamine has been modified chemically by removing one or two hydroxyl groups from the 2-deoxystreptamine moiety to give 5- and 6- deoxyneamines (5 and 10), as well as 5,6-dideoxyneamine (15). Their antimicrobial activities were determined against several microorganisms, including kanamycin-resistant strains.