Amides of de-acetylglucosaminyl-deoxy teicoplanin active against highly glycopeptide-resistant enterococci. Synthesis and antibacterial activity.

Removal, by selective reduction, of the acetylglucosamine from teicoplanin A2-2 (CTA/2) produced the 34-de(acetylglucosaminyl)-34-deoxy pseudoaglycone (II). This compound was more active in vitro than CTA/2 against coagulase-negative staphylococci (CNS). Amide derivatives obtained by condensation of the carboxyl group of II with primary amines were particularly active against Streptococcus pyogenes and had some in vitro activity against VanA enterococci highly resistant to both teicoplanin and vancomycin. Among them, a carboxamide (VII) with a branched tetramine also had better activity than the corresponding amide of teicoplanin against CNS. In contrast, the dimethylamide (VIII) of II had little activity against VanA enterococci. While the overall structure of the heptapeptide backbone of the secondary carboxamides of II is the same as in CTA/2 and its amide derivatives, in deoxy pseudoaglycone II and its tertiary amide VIII the 51,52-peptide bond undergoes a conformational change from the original cisoid to the transoid orientation. This difference between the secondary amides of II and dimethylamide VIII is reflected in their different antibacterial spectrum. The direct synthesis of the amides of deoxy pseudoaglycone II from parent CTA/2-amides by reaction with sodium borohydride is also described.

Chemical modifications of the antibiotic purpuromycin.

Purpuromycin, isolated in our laboratories from the culture broth of Actinoplanes ianthinogenes, is very active in vitro against Gram-positive bacteria and fungi and shows variable activity against Gram-negative bacteria. Its poor bioavailability, probably due to its insolubility in aqueous media at physiological pH's, and the fact that its activity is antagonized by serum, led us to plan a chemical program with the aim of understanding the relevance of the substituents for the antibiotic activity. The original 7-methoxycarbonyl group was transformed into more hydrophilic groups by hydrolysis, by reduction and by ammonolysis or in esters with different degree of lipophilicity and steric hindrance. Almost all of the derivatives retained activity against Gram-positive bacteria but lost activity against Escherichia coli and Trichophyton mentagrophytes. Like purpuromycin, all of the derivatives show a reduced activity in the presence of serum.

N63-carboxamides of N15-alkyl and N15,N15-dialkyl derivatives of teicoplanin and deglucoteicoplanin.

The synthesis and biological properties of a series of N63-carboxamides of 15-N-alkylated derivatives of teicoplanin A2 (CTA) and its aglycone (TD) are described. Among the compounds, those carrying hydrophilic groups or ionizable amino functions on the N15-alkyl chain are more soluble in water than parent N15-methylated or unmodified amides. Selected compounds were more active in vitro than CTA or TD, and a few of them were also slightly more efficacious in vivo than the parent antibiotics in streptococcal septicemia in the mouse. Their degree of activity varied with the structure and length of the N15-alkyl chains.

Isolation, structure determination and biological activity of A-16686 factors A' 1, A' 2 and A' 3 glycolipodepsipeptide antibiotics.

When Actinoplanes strain ATCC 33076, the producer of A-16686 A1, A2 and A3 complex, is fermented in a suitable medium three additional factors, designated A' 1, A' 2 and A' 3 are produced. These were isolated and characterized, and were shown to differ from the parent components of the original complex by lacking one mannose unit. Bioconversion of A factors into A' factors was achieved by incubation with the mycelium of Actinoplanes ATCC 33076. Factor A' 2 has better antibacterial activity than A2 against some bacteria.

Synthesis and antibacterial activity of a series of basic amides of teicoplanin and deglucoteicoplanin with polyamines.

Basic carboxamides of teicoplanin A2 (CTA) and its aglycon (TD) are prepared by condensation of the 63-carboxyl function of these antibiotics with linear or branched polyamines. The antimicrobial activities of some of the resulting compounds were better than those of the unmodified antibiotics. The presence of more than one basic group in the amidic chain enhanced the in vitro activity of some TD-amides against Gram-negative bacteria; two of these derivatives were also effective in vivo against Escherichia coli septicemia in the mouse. Among the CTA derivatives, the amide with spermine showed some unexpected in vitro activity against Gram-negatives. Both CTA- and TD-amides with polyamines are very soluble in water over a wide range of pH and are very hydrophilic.

Antibiotic GE2270 a: a novel inhibitor of bacterial protein synthesis. II. Structure elucidation.

GE2270 A, produced by Planobispora rosea ATCC 53773, inhibits Gram-positive bacteria and anaerobes by acting on the bacterial protein synthesis. The structure has been determined by physico-chemical methods applied to the intact molecule and to the main hydrolysis products. Characterization by UV, IR, NMR (double quantum filter COSY), acid-base ionization, elemental analysis and FAB-MS indicated that GE2270 A is a highly modified peptide having MW 1,289 and formula C56H55N15O10S6, and a weak basic function, and that it belongs to the thiazolyl peptide group of antibiotics. Acid hydrolysis yielded a main product (MW 634), responsible for the chromophoric absorption, and a number of hydrolyzed products of lower MW. 13C NMR inverse techniques and MS studies (EI, positive ion chemical ionization, and collision induced dissociation FAB-MS-MS experiments) on GE2270 A, the chromophoric compound, and the other hydrolysis products led to the complete identification of the various amino acid residues and their sequence. Two out of the six chiral centers have been determined. The structure is thought to originate from modification of a chain of 14 amino acids in a process which creates 6 thiazole rings and one pyridine. The modification process also closes the linear polypeptide to form a cyclic part with an attached side-chain. GE2270 A plausibly has a similar biosynthetic origin to that of other thiazolyl peptide antibiotics such as nosiheptide and micrococcin.

Sequence determination of actagardine, a novel lantibiotic, by homonuclear 2D NMR spectroscopy.

By combination of several 1H NMR techniques, the sequence of actagardine has been elucidated. It has been shown that it is a tetracyclic 19-residue peptide antibiotic. It differs from the previously described lanthionine-containing peptide antibiotics belonging to the lantibiotic class.

N15-alkyl and N15,N15-dialkyl derivatives of teicoplanin antibiotics.

The synthesis and the biological properties of a series of N15-alkyl and N15,N15-dialkyl derivatives of teicoplanin A2, its pseudoaglycones and aglycone are described. The alkylation of the terminal amino group did not affect the ability of these teicoplanin derivatives to bind with Ac2-L-Lys-D-Ala-D-Ala, a synthetic model of the antibiotic's target peptide in bacterial cell walls, but influenced their in vitro and in vivo antimicrobial activities to a different extent, depending on the structure and length of the alkyl chains and the type and number of sugars present.

Ramoplanin: a review of its discovery and its chemistry.

Ramoplanin is a novel antibacterial agent with characteristics that make it suitable for development as a topical treatment for acne, infected wounds, and for treatment of antibiotic-associated diarrhoea. In this paper, the authors will review the discovery process and the descriptive chemistry of this novel molecular entity.

Dechloro teicoplanin antibiotics.

Mono- and didechlorinated derivatives of the antibiotic teicoplanin, its pseudoaglycones and aglycone, and of one amide and ester of deglucoteicoplanin were prepared under selective reductive conditions. The selectivity and rate of dehalogenation were studied and compared to those of vancomycin and deglucovancomycin. The influence of the chlorine substituents on the mechanism of action and antibacterial activity of teicoplanin antibiotics was also investigated.

Ramoplanin (A-16686), a new glycolipodepsipeptide antibiotic. III. Structure elucidation.

By combination of chemical, 1H and 13C NMR, and mass spectrometric studies, the structures of the three components of the antibiotic ramoplanin (A-16686), produced by Actinoplanes sp. ATCC 33076, have been elucidated. All the components have structures formed by a common depsipeptide skeleton carrying a dimannosyl group and are differentiated by the presence of various acylamide moieties, derived from C8, C9 and C10 fatty acids.

Ramoplanin (A-16686), a new glycolipodepsipeptide antibiotic. IV. Complete sequence determination by homonuclear 2D NMR spectroscopy.

Homonuclear 2D NMR spectroscopy double quantum filter correlation spectroscopy (DQF-COSY), relayed-COSY, nuclear Overhauser enhancement spectroscopy (NOESY), and DQF-relayed-NOESY) allowed the complete determination of the core depsipeptide of antibiotic ramoplanin (A-16686). In particular, the DQF-relayed-NOESY experiments were essential in assigning the single signals close to the diagonal.

Isolation and structure determination of the main related substances of teicoplanin, a glycopeptide antibiotic.

Teicoplanin is a complex formed by five closely related glycopeptides and by a small amount of a hydrolysis product. Minor quantities of related substances are also present. Two of them (named RS-1 and RS-2) were isolated and purified starting from the tailing fractions of a teicoplanin batch. Preparative reversed-phase liquid chromatography on large low-pressure and medium high-pressure scales, concentration, desalting, and freeze-drying steps were applied. 300 mg of RS-1 and 900 mg of RS-2 were obtained in a purity grade (about 90%) sufficient for structural investigation. Starting from considerations on the HPLC retentivity and on biosynthesis, the structures were assigned on the basis of 1H-N.M.R. spectra and homonuclear CO-SY 2D experiments, FAB-MS spectrometry, and GC-MS of the esters of the fatty acids obtained by hydrolysis. RS-1 and RS-2 are teicoplanins having 10-methyl-undecanoic acid and n-dodecanoic acid, respectively as fatty acid chains. No major difference in the in vitro activity of these teicoplanins emerged in comparison with teicoplanin complex.

Teicoplanin, antibiotics from Actinoplanes teichomyceticus nov. sp. VII. Preparation and NMR characteristics of the aglycone of teicoplanin.

Several hydrolytic reactions that transform teicoplanin or its pseudo-aglycones into the aglycone with good yields are described. The most interesting approach is hydrolytic removal of the sugars in benzyl alcohol with the formation of the aglycone benzyl ester which is then submitted to hydrogenolysis. A detailed description of the 1H and 13C NMR spectra of the teicoplanin aglycone hydrochloride is presented. All the signals were attributed to the hydrogen and carbon atoms using homo and heteronuclear COSY. The relevant interactions through space between the hydrogen atoms were obtained by NOE. The structural aspects are discussed in terms of the well-known mechanism of action of the glycopeptide antibiotics.