4‑Toluenesulfonyloxymethyl‑(<i>H</i>)‑phosphinate: A Reagent for the Introduction of <i>O</i>- and <i>S</i>‑Methyl‑(<i>H</i>)‑phosphinate Moieties

The straightforward synthesis of sodium 4-toluene­sulfonyl­oxymethyl-(<i>H</i>)-phosphinate and (<i>H</i>)-phosphino­methyl­isothio­uronium tosylate as new reagents for the preparation of <i>O</i>- and <i>S</i>-methyl-(<i>H</i>)-phosphinic acid derivatives, respectively, is described. The reactivity of both reagents was demonstrated by the preparation of protected 2′-deoxy­ribonucleo­side-<i>O</i>-methyl-(<i>H</i>)-phosphinates in the 5′- and 3′-series and 2′,5′-dideoxy­ribonucleo­side-5′-<i>S</i>-methyl-(<i>H</i>)-phosphinates. These compounds represent a new class of monomers compatible with the solid phase synthesis of oligonucleotides by <i>H</i>-phosphonate chemistry, as it was proved with the synthesis of a fully phosphonate heptamer