Chemical aspects of penicillin allergy. The direct formation of penicilloyl determinants in penicillin

The aminolysis of two penicillin-like compounds which cannot form penicillenic acid has been studied:

• 1 6-Aminopenicillanic acid (which is highly immunogenic) reacts directly with ε-amino groups at pH 7,4 under CO₂-free conditions; the possible role of its polymerisation in this reaction remains to be studied.
• 2 6-Dinitrophenylamino-penicillanic acid reacts with εamino groups at pH 7,4 as fast as benzylpenicillin and other penicillins. Its immunogenicity in the rabbit is similar to that of benzylpenicillin.

     

Conversion of penicillin to cephalosporin lactones.

Penicillin G ( 1 , R ? CH₂Ph) was converted to cephaloram- and 6-epicephaloram lactones 11 and 12 respectively by the initial replacement of thiazolidine part of penicillin by the mercaptan 9 followed by intramolecular cyclization and subsequent introduction of double bond at C(3).     

Chemical aspects of penicillin allergy. The direct penicilloylation of epsilon-amino groups by penicillin at pH 7.4

The aminolysis of penicillins by ε-amino groups at pH 7,4 is demonstrated. It is shown that penicillenic acid, formed spontaneously under these conditions from penicillins, does not contribute significantly to the penicilloylations observed. Penicillin therefore can directly form penicilloylamides under physiological conditions.     

High-performance liquid chromatographic determination of penicillin G, penicillin V and cloxacillin in beef and pork tissues.

The objective was to develop confirmatory high-performance liquid chromatographic methods for penicillin residues in animal tissues with detection limits of less than or equal to 10 ng/g. A previously described procedure was modified by using a larger sample size and isocratic analysis. Tissues (15 g) were blended with 45 ml of water and 20 ml of homogenate were mixed with 40 ml acetonitrile and filtered. The filtrate (30 ml) was mixed with 10 ml of 0.2 M H3PO4 and extracted with methylene chloride. The combined methylene chloride layers were mixed with acetonitrile and hexane, washed with two 4-ml portions of water and then extracted with four 1-ml portions of 0.01 M phosphate buffer (pH 7). The combined buffer extracts were concentrated to 1 ml under reduced pressure. Analysis was isocratic during 0.01 M phosphate buffer (pH 7)-acetonitrile with proportions 85:15 (penicillin G), 82:18 (penicillin V) or 78:22 (cloxacillin). A polystyrene-divinylbenzene copolymer column, 150 x 4.6 mm I.D. (Polymer Labs. PLRP-S), was used with a flow-rate of 1 ml/min and detection at 210 nm. The presence of penicillins was confirmed by treating a duplicate sample with penicillinase. Recoveries were greater than 90% in most instances. Detection limits were 5 ng/g in muscle and higher in liver and kidney. The procedure is a simple and sensitive method for confirming the presence of penicillins in animal tissues.     

Structural studies on penicillin derivatives. X. Chlorination of azetidinone derivatives

The allylic methyl group of several azetidinone derivatives can be cleanly chlorinated by a mechanism which appears to be that of an ene-reaction.     

Adsorption properties of the penicillin derivative DTPA on gold substrates.

Despite the large number of articles and patents dealing with penicillin and other beta-lactam antibiotics, there have been no reports about the self-assembly of such substances as monolayers on gold surfaces. The main reason stems from the high reactivity of the beta-lactam ring, which hinders the development of molecules possessing this entity together with a metal-anchoring function. Herein, we present the synthesis of a novel molecule, 6-[(R,S)-5-(1,2-dithiolan-3-yl)pentanoyl-amino]-penicillanic acid, which combines the beta-lactam ring and a metal-anchoring group. Using spectroscopic tools, we demonstrate the chemisorption of this compound on gold as self-assembled monolayers without any alteration of the penicillin pharmacophore and document its reactivity towards a penicillin-binding protein, BlaR-CTD. Our work is a preliminary step towards the development of new biosensors and well-ordered protein arrays, both based on the high affinity of penicillin for penicillin-binding proteins.     

Studies on residual antibacterials in foods. IV. Simultaneous determination of penicillin G, penicillin V and ampicillin in milk by high-performance liquid chromatography

A rapid and simple method for the simultaneous determination of penicillin G (PCG), penicillin V (PCV) and ampicillin (ABPC) in milk is described. The retention behaviour of these beta-lactam antibiotics in reversed-phase liquid chromatography with mobile phases containing sodium alkylsulphonate was studied. Good separations were obtained with methanol-water-0.2 M phosphate buffer (pH 4.0) (5:13:2) containing 11 mM sodium 1-heptanesulphonate and a LiChrosorb RP-18 column. The sample was pre-treated with a Sep-Pak C18 cartridge. The peaks corresponding to each beta-lactam antibiotics can be confirmed with the treatment using penicillinase. The recoveries from milk fortified with sodium PCG, potassium PCV and ABCP at levels of 0.5 and 0.1 micrograms/g each were generally better than 87% and the relative standard deviations were 1.17-4.98%. The detection limits corresponded to 0.03 microgram/g of these beta-lactam antibiotics in milk.     

Stability of penicillin antibiotic residues in meat during storage. Ampicillin

Incurred samples from a pig treated with ampicillin, one of the most important penicillin antibiotic drugs used in food-producing animal treatments, were analyzed at the residue level of the drug in muscle tissue (approximately 100 microg kg(-1)) during their freezing storage and using three different techniques: quantitative microbiological assay, HPLC-UV and LC-MS. Two parameters have been specifically monitored: storage temperature (-20 and -75 degrees C) and storage packaging (ground meat or bulk meat). No significant decrease was observed during the first 3 months of storage monitoring at -20 and -75 degrees C. On the contrary, the sample preparation significantly affected the drug concentration in muscle from the very beginning of the storage. Grinding the meat before storage allowed to keep the drug near the higher level of concentration (approximately 100 microg kg(-1)) when bulk meat stored frozen systematically led to a decreased value (approximately 75 microg kg(-1)). After 8 months of storage at -20 degrees C, a significant decrease arose and was never observed at -75 degrees C. All the results were similarly obtained with the three different techniques used simultaneously, which allows to indicate a good correlation between the techniques.     

Structural studies of penicillin acylase

Penicillin acylases are used in the pharmaceutical industry for the preparation of antibiotics. The 3-D structure of Penicillin Gacylase from Escherichia coli has been solved. Here, we present structural data that pertain to the unanswered questions that arose from the original strucutre. Specificity for the amide portion of substrate was probed by the structure determination of a range of complexes with substitutions around the phenylacetyl ring of the ligand. Altered substrate specificity mutations derived from an in vivo positive selection process have also been studied, revealing the structural consequences of mutation at position B71. Protein processing has been analyzed by the construction of site-directed mutants, which affect this reaction with two distinct phenotypes. Mutations that allow processing but yield inactive protein provide the structure of an ES complex with a true substrate, with implications for the enzymatic mechanism and stereospecificity of the reaction. Mutations that preclude processing have allowed the structure of the precursor, which includes the 54a mino acid linker region normally removed from between the A and B chains, to be visualized.     

New spiro derivatives of penicillin

The first example of carbenoid ring expansion of thiophene to a 2H-thiopyran has been observed in its Rh-catalysed reaction with benzhydryl 6-diazopenicillanate. Buchner ring expansion of anisole with the same carbenoid gives two isomeric methoxy-cycloheptatrienes by attack on the upper face of the β-lactam ring. In one of the isomers, the methoxyl group shows a strong conformational preference in solution, revealed by n.O.e. difference speotroscopy.     

Analysis of wine for penicillin

This study addresses the question of whether the antibiotic Penicillin, which is produced by the common mold Penicillium notatum, could possibly become a contaminate of wine during the fermentation process. The significance of this study is related to the potential health effects this agent might produce in those consumers who have an allergic response to Penicillin. It has been estimated that between 6% and 8% of the American population is subject to this type of allergic response. A method is developed for the detection of penicillin in wines using high-pressure liquid chromatography. We demonstrate that penicillin G hydrolyzes rapidly in wine with first-order kinetics, and the half-life of this antibiotic is 147 min in a typical commercial wine. An analysis of a number of commercial wines shows no evidence of the presence of penicillin, which should negate the question of any allergic response associated with this potential contaminate.     

The trapping of sulfenic acids from penicillin sulfoxides. Ethyl 2-mercaptoacetate

The thermolysis of trichloroethyl 6-phenoxyacetamido penicillanate sulfoxide and ethyl 2-mercaptoacetate in toluene gave the unsym-azetidinone disulfide(β,γ-isomer) in 65% yield. With added catalytic amounts of N,N-dimethylaniline the α,β-isomer was the major product (60%), along with a $\text{new}$ β-lactam cleaved product, $\text{8}$ (5–6%).