Iron Dienylphosphate Tricarbonyl Complexes as Water-Soluble Enzyme-Triggered CO-Releasing Molecules (ET-CORMs)

A series of racemic phosphoryloxy-substituted (η4-cyclohexadiene)­Fe­(CO)3 complexes was synthesized
by exploiting
the O-phosphorylation of (dienol)­Fe­(CO)3 intermediates
generated in situ from the corresponding triisopropylsiloxy-protected
complexes. The phosphorylated products were fully characterized by
spectroscopic methods, including single-crystal X-ray diffraction
in four cases. Monodeprotection of two dimethyl phosphate derivatives
with trimethylamine led to the tetramethylammonium salts of the (cyclohexadienyl
methyl phosphate)­Fe­(CO)3 complexes. These compounds are
the first water-soluble enzyme-trigged CO-releasing molecules (ET-CORMs).
The phosphatase-induced CO release was monitored by means of GC. The
biological activity was assessed in different cellular assays. The
compounds were shown to be only slightly toxic, and a moderate anti-inflammatory
potential was determined in an assay based on the inhibition of inducible
NO synthase (iNOS)-induced NO production.