Hypervalent iodine in synthesis 92. A facile synthesis of 3-substituted-5,6-dihydroimidazo[2,1-b]thiazoles by cyclocondensation of alkynyl(phenyl)iodonium salts and imidazolidine-2-thione

A simple method for the synthesis of 3-substituted 5,6-dihydroimidazo[2,1-b]thiazoles is achieved by cyclocondensation of alkynyl(phenyl)iodonium salts with imidazolidine-2-thione.

Hypervalent Iodine in Synthesis. 94. A Facile Synthesis of 2-Substituted-imidazo[1,2-a]pyridines by Cyclocondensation of Alkynyl(phenyl) iodonium Salts and 2-Aminopyridine

A facile method for the synthesis of 2-substituted-imidazo[1,2-a]pyridines is achieved by cyclocondensation of alkynyl(phenyl)iodonium salts with 2-aminopyridine.

Hypervalent iodine in synthesis 93. A facile synthesis of 2-substituted imidazo[1,2-a]pyrimidines by cyclocondensation of alkynyl(phenyl)iodonium salts and 2-aminopyrimidine

Simple stirring of a mixture of the alkynyl(phenyl)iodonium salts 1 with 2-aminopyrimidine 2 in chloroform under reflux for two hours in the presence of K2CO3 gave, after workup, the 2-substituted imidazo[1,2-]pyrimidines 3 in moderate to good yields. A possible mechanism for the formation of 3 involves the intramolecular cyclization of the intermediate alkylidenecarbene 6.

Hypervalent iodine in synthesis. 90. A mild and efficient method for the iodination of pyrazoles

The combined reagent of iodobenzene diacetate (or polymer-supported iodobenzene diacetate) with iodine was used as an effective iodinating agent of pyrazoles to the corresponding 4-iodopyrazole derivatives at room temperature with high yields.

Hypervalent iodine in synthesis 91: a mild and efficient method for the halogenation of 6-methyluracil derivatives

The combined reagent of iodobenzene diacetate (or polymer-supported iodobenzene diacetate) with iodine or bromine was used as an effective halogenative agent of 6-methyluracil derivatives to the corresponding 5-halo-6-methyluracil derivatives at room temperature with high yields.

Hypervalent iodine in synthesis 64:Syntheses of diaryl selenides and alkyl aryl selenides by palladium-catalyzed arylation of areneselenyl or alkaneselenyl magnesium bromide with diaryliodonium salt

Areneselenyl or alkaneselenyl magnesium bromide reacts rapidly with diaryliodonium salt to give the corresponding diaryl or alkyl aryl selenide in the presence of catalytic amounts of Pd-(PPh3)4 in good yield.

Novel reaction products from the hypervalent iodine oxidation of hydroxylated stilbenes and isoflavones

Novel reaction pathways for the hypervalent iodine-mediated oxidation of bioactive phenols containing extended conjugated π-systems are described. Oxidation of 4-hydroxystilbenes in methanol using a hypervalent iodine-based oxidant led to the formal 1,2-addition of methoxy groups across the central stilbene double bond. Treatment of the structurally related 4-hydroxyisoflavone with di(trifluoroacetoxy)iodobenzene leads to the surprising formation of 2,4′-dihydroxybenzil. Potential mechanisms for these new reaction pathways are discussed, and the X-ray crystal structure of 2,4′-dihydroxybenzil is presented. In contrast, oxidation of the corresponding 3-hydroxystilbenes and 3-hydroxyisoflavone led to conventional dienone oxidation products. The antitumour implications of these oxidation processes are briefly highlighted; the novel 4-substituted phenolic oxidation products were found to be inactive in terms of in vitro antitumour cellular activity, whereas the 3-substituted phenol products gave novel agents with potent and enhanced antitumour activity in the HCT 116 cancer cell line. © The Royal Society of Chemistry 2005.

The significance of hand wash compliance on the transfer of dermal lipids in contact lens wear

Aim: The aim of this study was to assess the impact of hand washing regimes on lipid transference to contact lenses. The presence of lipids on contact lenses can affect visual acuity and enhance spoilation. Additionally, they may even mediate and foster microbial transfer and serve as a marker of potential dermal contamination. Methods and materials: A social hand wash and the Royal College of Nursing (RCN) hand wash were investigated. A 'no-wash regime' was used as control. The transfer of lipids from the hand was assessed by Thin Layer Chromatography (TLC). Lipid transference to the contact lenses was studied through fluorescence spectroscopy (FS). Results: Iodine staining, for presence of lipids, on TLC plates indicated the 'no-wash regime' score averaged at 3.4 ± 0.8, the social wash averaged at 2.2 ± 0.9 and the RCN averaged at 1.2 ± 0.3 on a scale of 1-4. The FS of lipids on contact lenses for 'no washing' presented an average of 28.47 ± 10.54 fluorescence units (FU), the social wash presented an average of 13.52 ± 11.12. FU and the RCN wash presented a much lower average 6.47 ± 4.26. FU. Conclusions: This work demonstrates how the method used for washing the hands can affect the concentration of lipids, and the transfer of these lipids onto contact lenses. A regime of hand washing for contact lens users should be standardised to help reduce potentially transferable species present on the hands. © 2011 British Contact Lens Association.

Evaluation of a 2% chlorhexidine gluconate in 70% isopropyl alcohol skin disinfectant

The efficacy of a new skin disinfectant, 2% (w/v) chlorhexidine gluconate (CHG) in 70% (v/v) isopropyl alcohol (IPA) (ChloraPrep®), was compared with five commonly used skin disinfectants against Staphylococcus epidermidis RP62A in the presence or absence of protein, utilizing quantitative time-kill suspension and carrier tests. All six disinfectants [70% (v/v) IPA, 0.5% (w/v) aqueous CHG, 2% (w/v) aqueous CHG, 0.5% (w/v) CHG in 70% (v/v) IPA and 10% (w/v) aqueous povidone iodine (PI)] achieved a log10 reduction factor of 5, in colony-forming units/mL, in a suspension test (exposure time 30 s) in the presence and absence of 10% human serum. Subsequent challenges of S. epidermidis RP62A in a biofilm (with and without human serum) demonstrated reduced bactericidal activity. Overall, the most effective skin disinfectants tested against S. epidermidis RP62A were 2% (w/v) CHG in 70% IPA and 10% (w/v) PI. These results suggest that enhanced skin antisepsis may be achieved with 2% (w/v) CHG in 70% (v/v) IPA compared with the three commonly used CHG preparations [0.5% (w/v) aqueous CHG, 2% (w/v) aqueous CHG and 0.5% (w/v) CHG in 70% (v/v) IPA]. © 2005 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved.

The mechanisms of melt stabilisation of polyolefins

The effects of melt stabilisers on the oxidative degradation of polyolefins (polypropylene, low density polyethylene) have been studied under a variety of processing conditions . The changes in the both chemical and physical properties of unstabilised polymers occurring during processing were found to be strongly dependent on the amount of oxygen present in the mixer. 2 ,6 ,3' ,5' -tetra-tert-butyl-4'-phenoxy-4-methylene-2, 5-cyclohexadiene-1- one (galvinoxyl), iodine, nitroxyl radicals and cupric stearate were found to be very efficient melt stabilisers particularly when processed in a restricted amount of air. The mechanisms of their melt stabilising action have been investigated and a common cyclical regenerative mechanism involving both chain-breaking electron acceptor (CB-A) and chain-breaking electron donor (CB-D) antioxidant activity was found to be involved in each case. 2,6,3',5'-tetra-tert-butyl-4'-hydroxy phenyl-4-rrethylene-2,5-cyclohexadiene- 1-one (hydrogalvinoxy1), 4-hydroxy, 2,2,6, 6-tetra methyl-N-hydroxy piperidine and hydrogen iodide were formed together with olefinic unsaturation in the substrates during the melt processing of the polymers containing galvinoxyl, 4-hydroxy, 2,2,6, 6-tetra methyl piperidine oxyl and iodine respectively. No bonding of the melt stabilisers to the polymers was found to occur. Cupric stearate was found to undergo a similar redox reaction during its action as a melt stabiliser with the formation of unsaturation in the polymer. Evidence for the above processes is presented. The behaviours of melt stabilisers in the subsequent thermal and photooxidation of polyolefins have also been studied. Galvinoxyl which is very effective under both mild and severe processing canditions has been found to be an effective antioxidant during thermal oxidation (oven ageing) and it is also moderately good. as a photo-stabiliser. Iodine and cupric stearate acted efficiently during melt stabilisation of polymers, however they were both ineffective as thermo-oxidative antioxidants and UV stabilisers. Although the melt stabilisation effectiveness of stable nitroxyl radicals (e.g. 4-hydroxy, 2,2,6,6-tetra methyl piperidineoxyl and Bis- (2,2,6 ,6-tetra methyl-4- piperidinyl-N-oxyl) sebacate) is not as high as that of galvinoxyl during processing particularly in excess of air, they have been found to be much more efficient as UV stabilisers for polyolefins. The reasons for this are discussed.

Sensitivity of staphylococcus epidermidis to chlorhexidine and associated resistance properties

Staphylococcus epidermidis are common Gram-positive bacteria and are responsible for a number of life-threatening nosocomial infections. Treatment of S. epidermidis infection is problematic because the organism is usually resistant to many antibiotics. The high degree of resistance of this organism to a range of antibiotics and disinfectants is widely known. The aims of this thesis were to investigate and evaluate the susceptibility of isolates of S. epidermidis from various infections to chlorhexidine (CHX) and to other disinfectants such as benzalkonium chloride (BKC), triclosan (TLN) and povidone-iodine (PI). In addition, the mechanisms of resistance of S. epidermidis to chlorhexidine (the original isolates and strains adapted to chlorhexidine by serial passage) were examined and co-resistance to clinically relevant antibiotics investigated. In 3 of the 11 S. epidermidis strains passaged in increasing concentrations of chlorhexidine, resistance to the disinfectant arose (16-fold). These strains were examined further, each showing stable chlorhexidine resistance. Co-resistance to other disinfectants such as BKC, TLN and PI and changes in cell surface hydrophobicity were observed. Increases in resistance were accompanied by an increase in the proportion of neutral lipids and phospholipids in the cell membrane. This increase was most marked in diphosphatidylglycerol. These observations suggest that some strains of S. epidermidis can become resistant to chlorhexidine and related disinfectants/antiseptics by continual exposure. The mechanisms of resistance appear to be related to changes in membrane lipid compositions.

The toxic effects of anticholinesterases on muscle

It has been shown that acute administration of ecothiopate iodine in vivo caused an approximate 80% depression of acetylcholinesterase activity in the diaphragms of mice. Inhibition of acetylcholinesterase was accompanied by an influx of calcium at the junctional region of the diaphragm, which continued during subsequent progressive development of a severe myopathy located in the same region. Myopathy was accompanied by loss of creatine kinase from the muscle and was represented, at the light microscope level, by hypercontraction, Procion Yellow staining and loss of cross striations within the muscle fibres. It appeared to reach a point of maximum severity approximately 3-6 hours after ecothiopate administration and then, by means of some repair/regeneration process, regained an apparently normal morphology within 72 hours of the intoxication. At the ultrastructural level, ecothiopate-induced myopathy was recognised by loss of Z-lines, swelling and vacuolation of mitochondria and sarcoplasmic reticulum, dissarray of myofilaments, crystal formation, and sometimes, by the complete obliteration of sarcomeric structure. The development of myopathy in vitro was shown to be nerve-mediated and to require a functional acetylcholine receptor for its development It was successfully treated therapeutically in vivo by pyridine-2-aldoxime methiodide and prophylactically by pyridostigmine bromide. However, the use of a range of membrane-on channel blockers, and of leupeptin, an inhibitor of calcium-activated-neutral-protease, have been unsuccessful in the prevention of ecothiopate-induced myopathy.

Oxidation effects on tetrahydropterin metabolism

The susceptibility of tetrahydropterins to oxidation was investigated in vitro and related to in vivo metabolism. At physiological pH, tetrahydrobiopterin (BH4) was oxidized, with considerable loss of the biopterin skeleton, by molecular oxygen. The hydroxyl radical (.OH) was found to increase this oxidation and degradation, whilst physiological concentrations of glutathione (GSH) retarded both the dioxygen and .OH mediated oxidation. Nitrite, at acid pH, oxidized BH4 to biopterin and tetrahydrofolates to products devoid of folate structure. Loss of dietary folates, from the stomach, due to nitrite mediated catabolism is suggested. The in vivo response of BH4 metabolism to oxidising conditions was examined in the rat brain and liver. Acute starvation depressed brain biopterins and transiently BH4 biosynthetic and salvage (dihydropteridine reductase, DHPR) pathways. Loss of biopterins, in starvation, is suggested to arise primarily from catabolism, due to oxygen radical formation and GSH depletion. L-cysteine administration to starving rats was found to elevate tissue biopterins, whilst depletion of GSH in feeding rats, by L-buthionine sulfoximine, decreased biopterins. An in vivo role for GSH to protect tetrahydropterins from oxidation is suggested. The in vivo effect of phenelzine dosing was investigated. Administration lowered brain biopterins, in the presence of dietary tyrosine. This loss is considered to arise from p-tyramine generation and subsequent DHPR inhibition. Observed elevations in plasma biopterins were in line with this mechanism. In conditions other than gross inhibition of DHPR or BH4 biosynthesis, plasma total biopterins were seen to be poor indicators of tissue BH4 metabolism. Evidence is presented indicating that the pterin formed in tissue samples by acid iodine oxidation originates from the tetrahydrofolate pool and 7,8-dihydropterin derived from BH4 oxidation. The observed reduction in this pterin by prior in vivo nitrous oxide exposure and elevation by starvation and phenelzine administration is discussed in this light. The biochemical importance of the changes in tetrahydropterin metabolism observed in this thesis are discussed with extrapolation to the situation in man, where appropriate. An additional role for BH4 as a tissue antioxidant and reductant is also considered.

A randomized, prospective clinical trial to assess the potential infection risk associated with the PosiFlow® needleless connector

The microbial contamination rate of luers of central venous catheters (CVCs) with either PosiFlow® needleless connectors or standard caps attached was investigated. The efficacy of 70% (v/v) isopropyl alcohol, 0.5% (w/v) chlorhexidine in gluconate 70% (v/v) isopropyl alcohol and 10% (w/v) aqueous povidone-iodine to disinfect the intravenous connections was also assessed. Seventy-seven patients undergoing cardiac surgery who required a CVC as part of their clinical management were randomly allocated either needleless connectors or standard caps. Patients were also designated to receive chlorhexidine/alcohol, isopropyl alcohol or povidone-iodine for pre-CVC insertion skin preparation and disinfection of the connections. After 72 h in situ the microbial contamination rate of 580 luers, 306 with standard caps and 274 with needleless connectors attached, was determined. The microbial contamination rate of the external compression seals of 274 needleless connectors was also assessed to compare the efficacy of the three disinfectants. The internal surfaces of 55 out of 306 (18%) luers with standard caps were contaminated with micro-organisms, whilst only 18 out of 274 (6.6%) luers with needleless connectors were contaminated (P<0.0001). Of those needleless connectors disinfected with isopropyl alcohol, 69.2% were externally contaminated with micro-organisms compared with 30.8% disinfected with chlorhexidine/alcohol (P<0.0001) and 41.6% with povidone-iodine (P<0.0001). These results suggest that the use of needleless connectors may reduce the microbial contamination rate of CVC luers compared with the standard cap. Furthermore, disinfection of needleless connectors with either chlorhexidine/alcohol or povidone-iodine significantly reduced external microbial contamination. Both these strategies may reduce the risk of catheter-related infections acquired via the intraluminal route. © 2003 The Hospital Infection Society. Published by Elsevier Science Ltd. All rights reserved.

Chlorhexidine and the prevention of surgical site infection

Surgical site infections (SSI) are a prevalent health care-associated infection (HAl). Prior to the mid-19th century, surgical sites commonly developed postoperative wound complications. It was in the 1860's, after Joseph Lister introduced carbolic acid and the principles of antisepsis that postoperative wound infection significantly decreased. Today, patient preoperative skin preparation with an antiseptic agent prior to surgery is a standard of practice. Povidone-iodine and chlorhexidine gluconate are currently the most commonly used antimicrobial agents used to prep the patient's skin. In this current study, the epidemiology, diagnosis, surveillance and prevention of SSI with chlorhexidine were investigated. The antimicrobial activity of chlorhexidine was assessed. In in-vitro and in-vivo studies the antimicrobial efficacy of 2% (w/v) chlorhexidine gluconate (CHG) in 70% isopropyl alcohol (IPA) and 10% povidoneiodine (PVP-I) in the presence of 0.9% normal saline or blood were examined. The 2% CHG in 70% IPA solutions antimicrobial activity was not diminished in the presence of 0.9% normal saline or blood. In comparison, the traditional patient preoperative skin preparation, 10% PVP-I antimicrobial activity was not diminished in the presence of 0.9% normal saline, but was diminished in the presence of blood. In an in-vivo human volunteer study the potential for reduction of the antimicrobial efficacy of aqueous patient preoperative skin preparations compromised by mechanical removal of wet product from the application site (blot) was assessed. In this evaluation, 2% CHG and 10% povidone-iodine (PVP-I) were blotted from the patient's skin after application to the test site. The blotting, or mechanical removal, of the wet antiseptic from the application site did not produce a significant difference in product efficacy. In a clinical trial to compare 2% CHG in 70% IPA and PVP-! scrub and paint patient preoperative skin preparation for the prevention of SSI, there were 849 patients randomly assigned to the study groups (409 in the chlorhexidine-alcohol and 440 in the povidone-iodine group) in the intention-to-treat analysis. The overall surgical site infection was significantly lower in the 2% CHG in 70% IPA group than in the PVP-I group (9.5% versus 16.1 %, p=0.004; relative risk, 0.59 with 95% confidence interval of 0.41 to 0.85). Preoperative cleansing of the patient's skin with chlorhexidine-alcohol is superior to povidone-iodine in preventing surgical site infection after clean-contaminated surgery.