Unique intramolecular oxidative rearrangement N-nitrosation mechanism of non-heam iron-containing enzyme SznF

ABSTRACTNon-heam iron-dependent enzyme SznF catalyzes a critical step of the L-arginine derived guanidine group rearrangement to produce the N-nitrosourea pharmacophore in the process of SZN biosynthesis. The intramolecular oxidative rearrangement process is accomplished in the Fe(II)-containing active site located at the cupin domain of SznF, with which the catalytic mechanism remains elusive. In this work, density functional theory methods have been employed to investigate possible catalytic mechanisms of SznF. The N-nitrosation reaction in SznF was found to follow an energetically favorable pathway which includes six consecutive steps: (1) formation of FeII-superoxo species with dioxgen binding on the iron center; (2) superoxo group attacking on the Cε of substrate to form the peroxo-bridge complex; (3) Cε-Nω bond homolysis to release NωO; (4) peroxo bridge heterolytic cleavage; (5) deprotonation of by Fe-O group; (6) the couples with the NωO group and generates the N-nitroso product. The reaction proceeds in an unexpected way during which the electrons shuttle among two NO groups of the substrate and the peroxo moiety to promote Cε-Nω bond homolysis and O-O bond heterolysis sequentially without generating high-valent Fe-O species, which is distinct from any known reactions catalyzed by the iron-containing enzyme. The unusual mechanism of SznF shed light on the area of enzymatic N-nitrosation reactions.

How to make C–N bonds using boronic acids and their derivatives without transition metals

No need for transition-metal catalysis in amination, amidation, nitration or nitrosation reactions with boron derivatives as reagents.

Synthesis of some new 4-iminothiazolidine-2-ones as possible antioxidants agents

Novel N3 substituted derivatives of 4-iminothiazolidine-2-one were synthesised under the reactions of [2+3]cyclocondensation, thionation and aminolysis. The functionalisation of 3-phenyl-4-imino-thiazolydine-2-one was carried out in its C5 position under condensation Knoevenagel and nitrosation reactions. The antioxidant activity of the synthesised compounds was evaluated in vitro by the method of their scavenging effect on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. When compared with existing antioxidants, some of our compounds were found to be more potent.