Tris-ketol phosphates

Mixtures of 4-(difluoroiodo)toluene and anhydrous phosphoric acid form a nonisolated hypervalent iodine species, probably PhI(0H)(0P03H2), which reacts with silyl enol ethers producing tris-ketol phosphates. Interestingly, mono- or bis-ketol phosphates could not be obtained using the appropriate stoichiometry. 

In some reactions (difluoroiodo)arenes can be used as general oxidizing reagents. For example, Koser and coworkers applied a difluoroiodotoluene/phosphoric acid mixture as a reagent for direct conversion of silyl enol ethers into tris-ketol phosphates 166 (Scheme 3.69) [217]. 

There continue to be reports of potential prodrugs of biologically-active nucleoside-5 -phosphates. The S-acetyl-2-thioethyl ester 137 of d4T has been prepared, and undergoes esterase hydrolysis in the cell. The same team have also made the analogous derivative of AZT. A series of aromatic aminoacid phosphoramidates of AZT have been described as have bis-ketol AZT monophosphates and 4-acyloxybenzyl bis(nucleosid-5 -yl) phosphates of AZT and ddl. Phosphodi- and tri-esters incorporating both AZT and a metal-com-... 

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