Esterification equilibrium constants of arsonic and arsinic acids

Synthesis of Novel Arsonolipids and Development of Novel Arsonoliposome Types

Arsonolipids represent a class of arsenic-containing compounds with interesting biological properties either as monomers or as nanostructure forming components, such as arsonoliposomes that possess selective anticancer activity as proven by in vitro and in vivo studies. In this work, we describe, for the first time, the synthesis of novel arsono-containing lipids where the alkyl groups are connected through stable ether bonds. It is expected that this class of arsonolipids, compared with the corresponding ester linked, will have higher chemical stability. To accomplish this task, a new methodology of general application was developed, where a small arsono compound, 2-hydroxyethylarsonic acid, when protected with thiophenol, can be used in an efficient and simple way as a building block for the synthesis of arsono-containing lipids as well as other arsono-containing biomolecules. Thus, besides the above-mentioned arsonolipid, an arsono cholesterol derivative was also obtained. Both ether arsonolipid and arsono cholesterol were able to form liposomes having similar physicochemical properties and integrity to conventional arsonoliposomes. Furthermore, a preliminary in vitro anticancer potential assessment of the novel ether arsonolipid containing liposomes against human prostate cancer (PC-3) and Lewis lung carcinoma (LLC) cells showed significant activity (dose- and time-dependent), which was similar to that of the conventional arsonoliposomes (studied before). Given the fact that novel arsonolipids may be more stable compared to the ones used in conventional arsonoliposomes, the current results justify further exploitation of the novel compounds by in vitro and in vivo studies.

Trithioarsenites [(RS)3As], dithioarsonites [R-As(SR′)2] and thioarsinites [R2As-SR′]: Preparations, chemical, biochemical and biological properties

Contrary to P(V) compounds, As(V) compounds can very easily reduced by thiols to As(III) thiolates that are deemed to play a central role in the metabolism of arsenic and therefore a review on the preparation and properties of the title thiolates can be of interest. The preparation of trithioarsenites, dithioarsonites and thioarsinites involves reactions of a thiol with a proper As(V) or As(III) precursor via 4-centered transition states or a thiolate by SN2 mechanisms. Convenient precursors are the solids As2O3, arsonic and arsinic acids, although for the latter two acids the separation of the product from the co-produced disulfides can be problematic. Only a few crystal structures have been reported and involve only trithioarsenites. From their chemical properties, the hydrolyses, transthiolations and air oxidations are of particular interest from mechanistic and biochemical/biological points of view. Their nucleophilicity towards alkyl halides and acyl derivatives revealed unexpected behavior. Although these molecules have many free electron pairs only three reports were found pertaining to their reaction with metal cations (Hg2+) and metal carbonyls; the mercuric complexes being not characterized. Only a few studies appeared for the action of the title compounds towards enzymes, while the patent literature revealed that they have bactericidal, fungicidal and insecticidal activities for agricultural applications, some have antiparasitic activity on animals and a few are carcinostatic.