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By using quantum chemical methods (B3LYP/6-311+G(2df,p)//B3LYP/6-31G(d)), we investigated the structures of aplicyanin A, aplicyanin B, aplicyanin C, aplicyanin D, aplicyanin E, and aplicyanin F along with their protonated structures. The calculated gas phase proton affinities of aplicyanin A, aplicyanin C, and aplicyanin E are around -250 kcal mol −1 and therefore more than 10 kcal mol −1 higher as in typical proton sponges such as 1,8-bis(dimethylamino)naphthalene. The compounds aplicyanin B, aplicyanin D, and aplicyanin F show reduced proton affinities of approximately -240 kcal mol −1 because of the acetyl group being conjugated with the imine N = C moiety. Nucleus-independent chemical shift (NICS) calculations on the same level of theory do not show any peculiarities, and a reasonable correlation between the toxicity of aplicyanins and the gas phase proton affinity is not observed.

: Organoselenium chemistry has undergone extensive development during the past decades, mostly due to the unique chemical properties of organoselenium compounds that have been widely explored in a number of synthetic transformations, as well as due to the interesting biological properties of these compounds. Diselenides and selenocyanates constitute the promising classes of organoselenium compounds that possess interesting biological effects and that can be used in the preparation of other selenium compounds. The combination of diselenide and selenocyanate moieties with other biologically relevant molecules (such as heterocycles, steroids, etc.) is a way for the development of compounds with promising pharmaceutical potential. Therefore, the aim of this review is to highlight the recent achievements in the use of diselenides or selenocyanates as precursors for the synthesis of pharmaceutically relevant compounds, preferentially compounds with antitumor and antimicrobial activities.

A mild and efficient procedure for the oxyselenocyclization of unsaturated alcohols by treatment with phenylselenyl chloride using ionic liquids as solvents/catalyzers has been developed. The reaction proceeds instantaneously under mild conditions with absolute regioselectivity, using primary, secondary, tertiary, and aromatic alcohols, as well as monosubstituted, disubstituted, and trisubstituted alkenols. This procedure provides a new method for the synthesis of substituted tetrahydrofurans and tetrahydropyrans ethers, the precursors of many biologically active metabolites, avoiding the use of toxic and corrosive catalysts. There are no previous reports of seleniummediated cyclofuncionalization reactions in ionic liquids. Taking into the account the good results obtained with [MMIM][MSO 4 ], its ease preparation, low viscosity, low price, and its capacity to be recovered and reused, it was selected as the solvent/catalyzer. Quantum-chemical calculations (MP2(fc)/ 6-311 + G**//B3LYP/6-311 + G**) has shown that the intramolecular cyclization is promoted by the hydrogen bond formed between the ionic liquid anion and the hydroxyl group of the alkenol.