Witold Przychodzeń

NEW PRODUCTS OF REACTION OF LAWESSON'S REAGENT WITH DIOLS

Reaction of the Lawessons reagent (LR) with aliphatic 1,2- and 1,3-diols as well as with aromatic 2,2′-dihydroxybiphenyl led to new products. Stable di-tert-butylammonium salts of bis-anisyldithiophosphonic acids 6 were isolated and were then converted into unique 9-, 9-, and 10-membered cyclic disulfides 7 and into S,S-dimethyl esters 8. The salts of bis-anisyldithiophosphonic acids 6 were shown to be capable of splitting the disulfide bond of Ellmans reagent.

Isothiocyanates may chemically detoxify mutagenic amines formed in heat processed meat

Meat consumption represents a dietary risk factor increasing the incidence of common cancers, probably due to carcinogenic amines (HAAs) formed upon meat heating. Interestingly, cancers whose incidence is increased by meat consumption, are decreased in populations consuming brassica vegetables regularly. This inverse correlation is attributed to brassica anticarcinogenic components, especially isothiocyanates (ITCs) that stimulate detoxification of food carcinogens. However, ITC reactivity towards amines generating stable thioureas, may also decrease mutagenicity of processed meat. We confirmed here that combining meat with cabbage (fresh or lyophilized), in proportions found in culinary recipes, limited by 17-20% formation of HAAs and significantly lowered mutagenic activity of fried burgers. Moreover, MeIQx mutagenicity was lowered in the presence of ITCs, as well as for synthetic ITC-MeIQx conjugates. This suggests that formation of thioureas could lead to chemical detoxification of food carcinogens, reducing the cancer risk associated with meat consumption.

Simultaneous determination of individual isothiocyanates in plant samples by HPLC-DAD-MS following SPE and derivatization with N-acetyl-l-cysteine.

The procedure for the isothiocyanates (ITCs) determination that involves derivatization with N-acetyl-l-cysteine (NAC) and separation by HPLC was developed. Prior to derivatization, plant ITCs were isolated and purified using solid-phase extraction (SPE). The optimum conditions of derivatization are: 500μL of isopropanolic eluate obtained by SPE combined with 500μL of derivatizing reagent (0.2M NAC and 0.2M NaHCO3 in water) and reaction time of 1h at 50°C. The formed dithiocarbamates are directly analyzed by HPLC coupled with diode array detector and mass spectrometer if required. The method was validated for nine common natural ITCs. Calibration curves were linear (R(2)⩾0.991) within a wide range of concentrations and limits of detection were below 4.9nmol/mL. The recoveries were in the range of 83.3-103.7%, with relative standard deviations <5.4%. The developed method has been successfully applied to determine ITCs in broccoli, white cabbage, garden cress, radish, horseradish and papaya.

Crystal structures of eight- and ten-membered cyclic bis­anisyl­phosphono­thioyl disulfanes and comparison with their P-ferrocenyl analogues

Two new crystal structures of eight- and ten-membered cyclic bisanisylphosphonothioyl disulfanes have been determined and these are compared to the structures of their ferrocenyl analogues.

Efficient Selenenylation of Malonates Using Bis(phosphorothioyl) Diselenide

Abstract Bis(O,O-diisopropoxyphosphinothioyl) diselenide reacts readily and quickly with the sodium salt of malonates to give quantitatively stable sodium 2-(O,O-diisopropyl phosphorothioselenenyl)propanedioates. No traces of the corresponding C,C-diselenenylation products were detected. A standard aqueous workup procedure affords the products, albeit in poor yield (about 45%). It was proved that the reaction is reversible due to the presence of nucleophilic sodium O,O-diisopropylphosphoroselenothioate in the reaction mixture. The reaction conducted with methyl iodide as a coreactant significantly improved the yield of the selenenylated product up to 88%. In contrast to the respective C-(phenylselenenyl)malonate that undergoes thermal disproportionation, the diethyl 2-(O,O-diisopropyl phosphorothioselenenyl)propanedioate is stable and remains unchanged even after prolonged heating in boiling toluene. The mechanism of phosphorothioselenenylation of malonates is described. GRAPHICAL ABSTRACT