Structure of the antifungal nucleotide antibiotic phosmidosine

Abstract

The structure of phosmidosine (1), a novel proline-containing nucleotide antibiotic from Streptomyces durhameusis, active against the pathogenic fungus Botrytis cinerea, was determined by mass spectrometry and NMR spectroscopy. Homologs 2,3, and the isomer 4 were detected and characterized using approaches based principally on tandem mass spectrometry and combined liquid chromatography-mass spectrometry which permitted assignment of most structural features directly in the crude isolate without prior isolation of individual components. Conversion of 1-4 to the O-isopropylidene derivatives la-4a by a microscale procedure resulted in enhanced fast atom bombardment ionization (FAB) signal-to-background sensitivity. Collision-induced dissociation mass spectra were acquired from molecular ions and ion source-generated fragment ions and used in conjunction with FAB-deuterium exchange methods for the assignment of structural differences between la-4a.Phosmidosine is a new antifungal antibiotic recently isolated1 from culture filtrates of Streptomyces durhameusis. It exhibits specific inhibitory activity against spore formation of Botrytis cinerea, a world-wide pathogenic fungus which causes gray mold disease in a variety of fruits and vegetables. We report the structure of phosmidosine (1), the compound on which biological testing was carried out, and on two homologs (2, 3) and an isomer (4).Compared with a large number of known nucleoside antibiotics,3 four nucleotide antibiotics have been previously reported: agrocin-84 produced by Agrobacterium radiobacter,2 thuringiensin from Bacillus thuringiensis,3 fosfadecin from Pseudomonas viridiflava,4 and fosfocytocin from Pseudomonas fluorescens.* The culture fermentation conditions, isolation, microbiological properties, and a brief description of chemical properties of phosmidosine were published with an initial communication of structure l.1The structure determination of phosmidosine was hampered due to low isolation yield from fermentation cultures and chemical instability over a period of several weeks. As a consequence, much of the principal structural data were acquired using tandem mass spectrometry, which permitted a number of structural features of 1 and related compounds 2-4 to be deduced without chromatographic separation or prior isolation of individual components of the culture isolate. HPLC of a crude phosmidosine isolate, on which most mass spectrometry experiments were carried out, shows four principal constituents,5 corresponding to 1-4 as described in the following sections. Results and DiscussionThe exact molecular size and gross structural features of phosmidosine were established by high-resolution mass

Aspartyl-tRNA Synthetase Is the Target of Peptide Nucleotide Antibiotic Microcin C

“…The N-acylphosphoramidate functionality is found in several natural products such as phosmidosine (23) and agrocin 84 (24). The synthesis of aminoacyl adenylate analogs having N-acylphosphoramidate linkage has also been reported (25).…”

Asparagine Synthetase Chemotherapy

“…These findings therefore resulted in the development of efficient synthetic routes for preparing chemically stable analogs of acyladenylates (148)(149)(150) in the expectation that such compounds will exhibit antibacterial activity coupled with low mammalian toxicity (151,152). In light of these studies (145)(146)(147)(148)(149)(150), β-asparaginyladenylate 5 ( Figure 6) was synthesized (153) The relatively lengthy synthetic route to obtain this compound and the presence of a charged phosphoamidate functional group argue against its likely clinical utility. In addition, the coupling reaction was insufficiently robust for use in constructing molecular libraries that could be assayed for ASNS inhibitory activity using modern highthroughput screening methods (154)(155)(156)(157).…”

Synthesis and Characterization of New Variously Substituted Allylic Phosphates

“…Melting points were measured using an "Electrothermal 9100" apparatus and are uncorrected. 1 19 F NMR spectroscopy. Infrared spectra were obtained using a YL2000 FT-IR spectrometer.…”