Contact dermatitis to metals

Metals are in close contact with skin and mucous membranes on a repeated, if not constant, basis. Nickel and mercury, well-recognized causes of contact dermatitis; gold and palladium, recently gaining acceptance as patch test allergens on standard screening trays; and cobalt are reviewed in this article. Sensitization to nickel, the most frequently identified allergen on patch testing, is associated with ear piercing. Contact with this potential allergen is ubiquitous. Mercury may be encountered as organic mercury in thimerosal, used as an antiseptic and a preservative in topical medications and vaccines, and metallic mercury found in dental amalgam and thermometers. Both forms may cause contact dermatitis. Gold, recognized as a frequent sensitizer, has been implicated in some cases of eyelid, patchy diffuse and oral lichenoid dermatitis. Cobalt allergy, found frequently in patients who are nickel allergic, also has been associated with ear piercing. Palladium sensitivity is often associated with nickel allergy. However, the incidence of clinical relevance is yet to be established.     

不同金属材料PFM影响牙龈的相关研究

目的:研究不同金属烤瓷全冠在临床中对牙龈的影响。方法:在患者自愿配合研究的基础上选取136颗基牙分为四组进行PFM修复,A组PFM修复中所用金属材料为钴铬合金,B组所用为金钯合金,C组所用为钛合金,D组选用钯银合金。修复前及修复后3个月、6个月、12个月对受试者进行临床检查,项目包括检测菌斑指数、AST水平、牙龈指数。结果:A、C、D组患者修复后各时间段的检测指标与修复前比较无显著差异(P>0.05),B组患者在修复后12个月时菌斑指数、AST水平、及牙根指数与修复前及B组均具有显著差异(P<0.05)。结论:金钯合金烤瓷全冠较其他合金烤瓷全冠对牙周组织的损伤更小,有利于牙龈的健康及修复体使用寿命的延长。     

Palladium‐catalyzed hydroxycarbonylation as the key step in the synthesis of a carbon‐14 labeled Maxi‐K channel blocker

Carbon‐14 labeled sodium formate was utilized for the preparation of a radiolabeled tracer to support the development of a Maxi‐K channel blocker. Key to the process was a palladium‐catalyzed hydroxycarbonylation of a bromoarene for installation of the radiolabel. Copyright © 2010 John Wiley & Sons, Ltd.     

Convenient methods for the synthesis of d4, d2 and d6 isotopomers of 4‐(4‐fluorobenzyl)piperidine

Pure 4‐(4‐fluoro‐[2,3,5,6‐²H₄]benzyl)piperidine was prepared via the Grignard reaction of 4‐fluoro‐[2,3,5,6‐²H₄]bromobenzene and pyridine‐4‐aldehyde followed by consecutive deoxygenation and heteroatomic ring saturation in the presence of palladium on carbon catalyst. An improved method for the catalytic H/D exchange in benzylic positions of 4‐(4‐fluorobenzyl)piperidine and its d₄ derivative has also been described. Copyright © 2005 John Wiley & Sons, Ltd.     

Elemental release from CoCr and NiCr alloys containing palladium

Purpose: An entirely new subclass of casting alloy composition whereby palladium (～approximately 25 wt%) is added to traditional base metal alloys such as CoCr and NiCr was recently introduced to the market. The purpose of this study was to evaluate the elemental release of new CoPdCr and NiPdCr alloys and compare them to traditional CoCr and NiCr alloys. Materials and Methods: Five casting alloys were investigated: CoPdCr‐A (NobleCrown NF, The Argen Corporation), CoPdCr‐I (Callisto CP+, Ivoclar Vivadent), NiPdCr (NobleCrown, Argen), CoCr (Argeloy N.P. Special, Argen), and NiCr (Argeloy N.P. Star, Argen). Rectangular specimens (n = 6/alloy) were prepared and immersed in a lactic acid/NaCl solution at 37°C for 7 days according to ISO 10271. Solutions were analyzed with ICP‐AES to determine elemental release. The concentrations of major ions (cobalt, nickel, palladium, chromium, and molybdenum) were compared using a generalized linear model (p < 0.05). Representative specimens were examined with optical microscopy before and after immersion. Results: The CoPdCr alloys released a significantly greater amount of respective ions (Co, Cr, Mo, and total ions) compared to the traditional CoCr alloy. No significant differences in elemental release were noted between NiPdCr and NiCr. Optical microscopic examination showed abundant areas of corrosion in the palladium‐containing CoCr alloys after immersion, whereas little difference was observed for the other alloys. Conclusions: Corrosion resistance measured via elemental release was compromised when CoCr was alloyed with palladium, but this effect was not observed with NiCr.     

Synthesis of 1‐(2′‐deoxy‐2′‐fluoro‐β‐D‐arabinofuranosyl)‐[Methyl‐11C]thymine ([11C]FMAU) via a Stille cross‐coupling reaction with [11C]methyl iodide

1‐(2′‐deoxy‐2′‐fluoro‐β‐D‐arabinofuranosyl)‐[methyl‐¹¹C]thymine ([¹¹C]FMAU) [¹¹C]‐ 1 was synthesised via a palladium‐mediated Stille coupling reaction of 1‐(2′‐deoxy‐2′‐fluoro‐β‐D‐arabinofuranosyl)‐5‐(trimethylstannyl)uracil 2 with [¹¹C]methyl iodide in a one‐pot procedure. The reaction conditions were optimized by screening various catalysts and solvents, and by altering concentrations and reaction temperatures. The highest yield was obtained using Pd₂(dba)₃ and P(o‐tolyl)₃ in DMF at 130°C for 5 min. Under these conditions the title compound [¹¹C]‐ 1 was obtained in 28±5% decay‐corrected radiochemical yield calculated from [¹¹C]methyl iodide (number of experiments=7). The radiochemical purity was >99% and the specific radioactivity was 0.1 GBq/μmol at 25 min after end of bombardment. In a typical experiment 700–800 MBq of [¹¹C]FMAU [¹¹C]‐ 1 was obtained starting from 6–7 GBq of [¹¹C]methyl iodide. A mixed ¹¹C/¹³C synthesis to yield [¹¹C]‐ 1 /(¹³C)‐ 1 followed by ¹³C‐NMR analysis was used to confirm the labelling position. The labelling procedure was found to be suitable for automation. Copyright © 2002 John Wiley & Sons, Ltd.     

A general route for 13C‐labeled fluorenols and phenanthrenols via palladium‐catalyzed cross‐coupling and one‐carbon homologation

A series of ¹³C‐labeled polyaromatic hydrocarbons (PAHs), fluorenols and phenanthrenols were synthesized from commercially available ¹³C‐labeled starting material giving rise to M + 6 isotopomers. This was accomplished using key palladium‐catalyzed cross‐coupling and one‐carbon homologation strategies. The conditions for these reactions were optimized, and the new chemical routes are efficient in the number of chemical steps, can be scaled to afford gram quantities and occur in good yields based on the ¹³C label. These labeled compounds as precursors for more complex PAHs and are useful as internal standards in mass spectrometry and NMR spectroscopy studies for monitoring environmental contamination and biological exposure to PAHs and their metabolites.