title: A reversible pH-dependent intramolecular pyridine-aldehyde cyclization.
abstract: A dipicolylamine (DPA) attached to an aldehyde moiety cyclizes to form a pyridinium-fused heterocycle. This intramolecular reaction between the pyridine and aldehyde moieties is reversible, and the position of the equilibrium is controlled by pH. The fused-ring heterocycle is stabilized under acidic conditions, whereas the ring-opened form is the major species under basic conditions. The ring-closed form can be utilized as a masked aldehyde precursor to access a variety of functional metal chelators containing the DPA unit.
authors: Department of Chemistry, Massachusetts Institute of Technology. Cambridge, Massachusetts 02139, USA.
authors: Xiao-an
authors: XA
authors: Zhang
authors: Datong
authors: D
authors: Song
authors: Stephen J
authors: SJ
authors: Lippard
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D000588:Amines / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003500:Cyclization; D006571:Heterocyclic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D015394:Molecular Structure; D010848:Picolinic Acids / Q000737:chemistry*; D011726:Pyridinium Compounds / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: C501847:2,2'-dipicolylamine; D000447:Aldehydes; D000588:Amines; D006571:Heterocyclic Compounds; D010848:Picolinic Acids; D011726:Pyridinium Compounds