Received July 6, 2006

Abstract:

The synthesis and structural characterization of a new pro-chelating agent, isonicotinic acid [2-(4,4,5,5-tetramethyl-[1,3,2]dioxaborolan-2-yl)-benzylidene]-hydrazide (BSIH), are presented. BSIH only weakly interacts with iron unless hydrogen peroxide (H₂O₂) is present to remove the boronic ester protecting group to reveal a phenol that is a key metal-binding group of tridentate salicylaldehyde isonicotinoyl hydrazone (SIH). BSIH prevents deoxyribose degradation caused by hydroxyl radicals that are generated from H₂O₂ and redox-active iron by sequestering Fe³⁺ and preventing iron-promoted hydroxyl radical formation. The rate-determining step for iron sequestration is conversion of BSIH to SIH, followed by rapid Fe³⁺ complexation. The pro-chelate approach of BSIH represents a promising strategy for chelating a specific pool of detrimental metal ions without disturbing healthy metal ion distribution.

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