Synthesis and antibacterial activity of asparagine derivatives of aminobenzylpenicillin

N-(p-Tolyl-sulfon-yl)-l-asparagine

In the title compound, C₁₁H₁₄N₂O₅S, the amide O atom acts as a hydrogen-bond acceptor from a carboxyl­ate O atom and a secondary amino N atom. In addition, one of the sulfonyl O atoms and the carbonyl O atom of the carboxyl group also form hydrogen bonds with the primary amido N atom. These intermolecular hydrogen-bonding inter­actions give rise to a layer structure, with the layers parallel to the ac plane.

Polytheonamides A and B, Highly Cytotoxic, Linear Polypeptides with Unprecedented Structural Features, from the Marine Sponge,Theonellaswinhoei

Polytheonamides A and B are highly cytotoxic polypeptides with 48 amino acid residues isolated from the marine sponge, Theonella swinhoei. The structure of polytheonamide B was determined by spectral and chemical methods, especially extensive 2D NMR experiments, which resulted in the unprecedented polypeptide structure; the N-terminal glycine blocked with a 5,5-dimethyl-2-oxo-hexanoyl group, the presence of eight tert-leucine, three beta-hydroxyvaline, six gamma-N-methylasparagine, two gamma-N-methyl-beta-hydroxyasparagine, and beta,beta-dimethymethionine sulfoxide residues. More significantly, it has the sequence of alternating D- and L-amino acids. Polytheonamide A is an epimer of polytheonamide B differing only in the stereochemistry of the sulfoxide of the 44(th) residue.

Morphological changes and lysis induced by beta-lactams associated with the characteristic profiles of affinities of penicillin-binding proteins in actinobacillus pleuropneumoniae

Actinobacillus pleuropneumoniae, which was formerly classified in the genus Haemophilus, is a pathogen causing swine pleuropneumonia. We found that aspoxicillin showed strong activity and that meropenem had better lytic activity against this pathogen. In the present study, we for the first time identified penicillin-binding proteins (PBPs) of A. pleuropneumoniae in order to elucidate the relationship between the antibacterial and lytic activities of beta-lactam antibiotics and affinities of the PBPs. The competitive assay using (3)H-labeled benzylpenicillin revealed seven PBPs in A. pleuropneumoniae; they were determined to be PBPs 1a, 1b, 2, 3, 4, 5, and 6, and the molecular masses of these PBPs were estimated to be 92, 80, 76, 72, 50, 44, and 30 kDa, respectively, by comparison with those of Haemophilus influenzae. Our detailed analysis of the affinities of the PBPs of A. pleuropneumoniae and of the bacterial lysis kinetics for several beta-lactam antibiotics revealed that the strong antibacterial activity of aspoxicillin against this strain could be related to the higher affinity of PBP 3 and that preferential inactivation of PBP 1b could cause rapid lysis.

Separation and determination of aspoxicillin in human plasma by micellar electrokinetic chromatography with direct sample injection

Both the separation and determination of aspoxicillin in human plasma by micellar electrokinetic chromatography (MEKC) were investigated. Selectivity in the separation of seven penicillin antibiotics was improved by using MEKC in comparison with capillary zone electrophoresis. Plasma proteins, which might interfere with drug analysis in conventional chromatography, were solubilized by the micelles employed in MEKC and eluted later than the drugs. This permitted the determination of the drugs in plasma by a direct sample injection method. One analysis of a plasma sample was performed within ca. 20 min without pretreatment. Good linearity and recovery were also obtained in the range of plasma levels usually encountered in clinical analysis with a correlation coefficient r = 0.999 and 94-104% recovery. The limit of detection for aspoxicillin was 1.3 micrograms ml-1 at a signal-to-noise ratio of 3.