Preparation of trimethyl‐2‐hydroxyethylarsonium (arsenocholine) compounds

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Abstract
Trimethyl‐2‐X‐ethylarsonium salts (X=OH, Cl, Br, CH3COO; anion=Br) and trimethyl‐2‐diethoxyethylarsonium bromide were prepared from trimethylarsine and the appropriate organic bromides in sealed tubes at elevated temperatures or by refluxing the neat reagents. The yields ranged from 33 to 85%. Anion exchange reactions produced the arsonium iodides, nitrates, acetates, tosylates, tetraphenylborates, picrates, hydroxides, and carbonates. Arsenocholine bromide (X=OH) was phosphorylated with concentrated phosphoric acid. The product was isolated as the barium salt. Treatment of the barium salt with sulfuric acid yielded trimethyl‐2‐(dihydrogen phosphato)ethylarsonium bromide. These substances were synthesized to serve as precursors for arsenic‐ containing phospholipids and as standards for the chromatographic identification of arsenocholines. The synthesized compounds were characterized by elemental analyses and 1H and 13C NMR spectroscopy. The shifts of the arsenic compounds were compared with those of the corresponding nitrogen compounds and found to be sufficiently different to be used for the identification of these compounds in their mixtures.