9-IODOSO-10-PHENANTHROATE - STRUCTURE AND PHOSPHOROLYTIC PROPERTIES OF A NONPLANAR IODOXOLONE

9-Iodoso-10-phenanthroic acid (IPA-OK) was prepared from 9-cyanophenan threne in a four-step, 44% overall yield synthesis, featuring cyano-di rected ortho lithiation/iodination as the key step. An X-ray crystal s tructure showed that TPA-OH exists in a phenanthroiodoxol-3(1H)-one va lence tautomeric form, 14-OH, characterized by T-shaped geometry at io dine, strong WO steric interactions between the peri-H atoms and the c arbonyl and iodoso oxygen atoms, a ''short'' endocyclic I-O bond, well -differentiated carbonyl and endocyclic C-O bond lengths, and nonplana rity in both the iodoxolone and phenanthrene rings (Figures 1 and 2). IPA-OH was an excellent catalyst for the cleavage of p-nitrophenyl dip henyl phosphate (PNPDPP) in aqueous micellar cetyltrimethylammonium ch loride (CTACl) solutions at pH 8 and 25 degrees C: 1 x 10(-5) M PNPDPP was cleaved by 1 x 10(-4) M IPA-OH in 3.5 x 10(-4) M CTACl with k(psi ) = 0.38 s(-1). Experiments in which [PNPDPP] > [IPA-OH] demonstrated that the catalyst ''turned over''; hydrolysis of the putative phosphor ylated IPA-OH intermediate was rapid.