Amino acids, di-and tri-peptides readily react with selenic acid (H 2 SeO 3 , formed during solution of selenium(IV) oxide in water) to give the corresponding ammonium hydroselenites. Most selenites synthesized are very active (0.4±11 mg ml À1) against mouse hepatoma MG-22A and readily increase NO concentration in the cultural medium on the HT-1080 line (up to TG 100 = 1500%). The amino-acid hydroselenites studied influenced the cell phenotype.

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The cyclization of substituted diaryl(hetaryl)alkynes with in‐situ‐prepared SeBr4 has been achieved. The use of an alkene additive as a bromine scavenger gives simple access to functionalized benzo[b]selenophene and selenophenothiophene derivatives from commercially available or easily accessible starting materials. The reactions can be performed in air without the use of moisture‐sensitive reagents, dry solvents, or an inert atmosphere. Mechanistic studies confirmed a regioselective anti 1,2‐addition in the selenobromination step, and a subsequent electrophilic substitution in the aromatic ring to complete the cyclization.

The cyclization of arylalkynes under selenobromination conditions, combined with an acid-induced 3,2-aryl shift, was elaborated as a general synthetic pathway for the preparation of polyhydroxy-2- and -3-arylbenzo[b]selenophenes from the same starting materials. The redox properties, free-radical-scavenging ability, and cytotoxicity against malignant cell lines (MCF-7, MDA-MB-231, HepG2, and 4T1) of the synthesized compounds were explored, and the obtained results were used to consider the structure-activity relationships (SARs) in these compounds. Consequently, the structural features that were responsible for the highly potent peroxyl-radical-scavenging activity were established.

Herein we report the first example of a strategy for peptide functionalization through the generation of selenocysteine electrophile in 5‐ and 6‐endo‐dig cyclization reactions. This simple approach allows bio‐conjugation of selenocystine‐based peptides. The developed protocol is based on copper(II) bromide mediated reactions of selenocystine with either 2‐propargyl N‐heterocycles through 5‐endo‐dig closure or with 2‐ethynylbiaryls through 6‐endo‐dig closure. It allows construction of indolizinium moiety on selenocysteine residue as well as formation of polyaromatic fragment bonded to selenium in a simple one‐pot process under mild reaction conditions.

A novel method for the cyclization of phenylalkyne derivatives (I) and (III) by selenobromination is developed to produce a variety of 3‐bromobenzo[b]selenophenes.

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