E. J. Behrman

The reaction of osmium tetroxide-pyridine complexes with nucleic acid components

Thymine and its derivatives react rapidly in aqueous solution with osmium tetroxide and pyridine to form stable bis(pyridine) osmate esters. We have studied these esters with the following pyrimidines: thymine, thymidine, thymidine-5′-phosphate, and uracil, using pyridine, 3-picoline, 3-chloropyridine, and 3-pyridyl mercuric acetate as the pyridine components. We have examined the kinetics of these reactions as a function of the concentration of substrate, pyridine, osmium tetroxide, and pH. The kinetic dependencies suggest the following rate expression:dP/dt=k1[OSO4·py][S]+k2[OSO4·py2][S]=k1β1[OSO4][py][S]+k2β2[OSO4][py]2[S] We report values for β1, β2, κ1, and κ2.

Fructose-asparagine is a primary nutrient during growth of Salmonella in the inflamed intestine.

Salmonella enterica serovar Typhimurium (Salmonella) is one of the most significant food-borne pathogens affecting both humans and agriculture. We have determined that Salmonella encodes an uptake and utilization pathway specific for a novel nutrient, fructose-asparagine (F-Asn), which is essential for Salmonella fitness in the inflamed intestine (modeled using germ-free, streptomycin-treated, ex-germ-free with human microbiota, and IL10−/− mice). The locus encoding F-Asn utilization, fra, provides an advantage only if Salmonella can initiate inflammation and use tetrathionate as a terminal electron acceptor for anaerobic respiration (the fra phenotype is lost in Salmonella SPI1− SPI2− or ttrA mutants, respectively). The severe fitness defect of a Salmonella fra mutant suggests that F-Asn is the primary nutrient utilized by Salmonella in the inflamed intestine and that this system provides a valuable target for novel therapies.

The guanosine 5′-diphosphate d-mannose:Guanosine 5′-diphosphate l-galactose epimerase of Chlorella pyrenoidosa: Chemical synthesis of guanosine 5′-diphosphate l-galactose and further studies of the enzyme and the reaction it catalyzes☆

An enzyme from extracts of the green alga Chlorella pyrenoidosa that catalyzes the reversible epimerization of guanosine 5′-diphosphate d-mannose to guanosine 5′-diphosphate l-galactose was further purified. The substrate guanosine 5′-diphosphate l-galactose was made chemically by the morpholidate procedure. An improved method was developed for the synthesis of an intermediate in that process, β-l-galactopyranosyl phosphate, via an orthoester of l-galactose. Various characteristics of the enzyme and the reaction it catalyzes were studied. A new method using gas-liquid chromatography was introduced for following the course of the reaction with unlabeled substrates.

The Elbs and Boyland-Sims peroxydisulfate oxidations

This paper reviews the recent literature on the title reactions and updates a 1988 review.

Studies on the mechanism of inhibition of bacterial ribonuclease P by aminoglycoside derivatives

Ribonuclease P (RNase P) is a Mg2+-dependent endoribonuclease responsible for the 5′-maturation of transfer RNAs. It is a ribonucleoprotein complex containing an essential RNA and a varying number of protein subunits depending on the source: at least one, four and nine in Bacteria, Archaea and Eukarya, respectively. Since bacterial RNase P is required for viability and differs in structure/subunit composition from its eukaryal counterpart, it is a potential antibacterial target. To elucidate the basis for our previous finding that the hexa-arginine derivative of neomycin B is 500-fold more potent than neomycin B in inhibiting bacterial RNase P, we synthesized hexa-guanidinium and -lysyl conjugates of neomycin B and compared their inhibitory potential. Our studies indicate that side-chain length, flexibility and composition cumulatively account for the inhibitory potency of the aminoglycoside-arginine conjugates (AACs). We also demonstrate that AACs interfere with RNase P function by displacing Mg2+ ions. Moreover, our finding that an AAC can discriminate between a bacterial and archaeal (an experimental surrogate for eukaryal) RNase P holoenzyme lends promise to the design of aminoglycoside conjugates as selective inhibitors of bacterial RNase P, especially once the structural differences in RNase P from the three domains of life have been established.

Reactions of cytosine and 5-methylcytosine with osmium(VIII) reagents: Synthesis and deamination to uracil and thymine derivatives

Abstract Cytosine and 5-methylcytosine react with osmium tetraoxide in the presence of 2,2′-bipyridyl or N,N,N′,N′-tetramethylethylenediamine to form oxoosmium (IV) esters by addition to the 5,6-double bond. These esters react with water to form the corresponding uracil and thymine derivatives by displacement of the exocyclic amino group.

The reactions of oxo-osmium ligand complexes with isopentenyl adenine and its nucleoside.

Abstract We report syntheses of oxo-osmium(VI)bis(ligand) esters of N6(Δ2isopentenyl) adenine (6-ipAde) and its nucleoside (IPA) which result from the addition of OsO4 to the double bond of the isopentenyl group. A study of the kinetics of these reactions shows that under typical conditions the rates of reaction relative to thymidine are as follows: for OsO4-pyridine: thymidine = 1; 6-ipAde = 4600: for OsO4-2, 2′-bipyridyl: thymidine = 380; 6-ipAde = 8600; IPA = 8600. We also report syntheses of osmate esters of IPA in which the osmium is bonded through the 2′- and 3′-hydroxyl groups of the ribose residue.

Synthesis of 4-Pyridone-3-sulfate and an improved synthesis of 3-Hydroxy-4-Pyridone

An improved synthesis of 3-hydroxy-4-pyridone via an Elbs oxidation of 4-pyridone and isolation of 4-pyridone-3-sulfate is described.

On the mechanism of the Elbs peroxydisulfate oxidation and a new peroxide rearrangement

Abstract Semiempirical calculations show that the intermediate formed by reaction between peroxydisulfate anion and the phenolate ion (the Elbs oxidation) is the species resulting from reaction of the tautomeric carbanion rather than the one resulting from attack by the oxyanion. This is confirmed by synthesis of the latter intermediate by reaction between Caros acid dianion (peroxymonosulfate) and some nitro-substituted fluorobenzenes. This intermediate rearranges preferentially to give the phenol ortho -sulfate rather than the para -sulfate characteristic of the Elbs oxidation. This reaction of an arylperoxysulfate to give a phenol ortho -sulfate is a new rearrangement.

Synthesis of glycosyl phosphates from sugar ortho esters: formation of bis(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyl) phosphate, and the effect of solvents on the synthesis of β-D-glucopyranosyl phosphate

Abstract Reaction of exo-3,4,6-tri-O-acetyl-1,2-O-(tert-butyl orthoacetyl)-α- D -glucopyranose with phosphoric acid and phosphorus pentaoxide in oxolane gave 2,3,4,6-tetra-O-acetyl-β- D -glucopyranosyl phosphate. Treatment of the reaction mixture with aqueous lithium hydroxide gave the expected β- D -glucopyranosyl phosphate. However, neutralization with ammonium hydroxide gave exclusively the phosphoric diester, namely, bis(2,3,4,6-tetra-O-acetyl-β- D -glucopyranosyl) phosphate. Formation the diester was traced to the phosphorus pentaoxide in the initial reaction-mixture. Study of solvents showed that phosphorylation of the ortho ester proceeds rapidly in a variety of ethers and N,N-dimethylamides.