A new, general one step synthesis of N-substituted benzisoselenazol-3(2H)-ones based on the reaction of o-iodobenzamides with lithium diselenide, is described. A series of alkyl and aryl derivatives was obtained in high yields (up to 98%). Their GPx-like antioxidant activity, tested by NMR, showed a significantly higher activity than ebselen.Scheme 1 Synthetic approaches to benzisoselenazol-3(2H)-one 1.

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New chiral camphane-derived benzisoselenazol-3(2H)-ones and corresponding diselenides have been synthetized using a convenient one-pot procedure. Se-N bond was efficiently converted to an Se-Se bond, which could also be easily re-oxidized to the initial benzisoselenazolone moiety. The antioxidant activity of camphor derivatives was evaluated and compared to the reactivity of a series of N-amino acid benzisoselenazol-3(2H)-ones obtained by a modified procedure involving the improved synthesis and isolation of the diseleno bis(dibenzoic) acid. The most efficient peroxide scavengers, N-bornyl and N-leucine methyl ester benzisoselenazol-3(2H)-ones, were further evaluated as cytotoxic agents on four cancer cell lines (MCF-7, HEP G2, HL 6, and DU 145) and normal cell line PNT1A. The highest antiproliferative potential was evaluated for two compounds bearing a 3-methylbutyl carbon chain, N-leucine methyl ester and N-3-methylbutyl benzisoselenazol-3(2H)-ones.

The mechanism of chirality transfer from a chiral alkyl substituent to a trityl moiety through sulfur or selenium atoms is analysed and discussed on the basis of ECD measurements, DFT structure and ECD spectra calculations. It is shown that the presence of a chalcogen atom is manifested by elongation of the distance between the chiral and the trityl moieties as well as by the change of electronic properties of the trityl chromophore while maintaining its chiroptical response to the chirality of the molecule.