Synthesis of new α or γ-functionalized hydroxymethylphosphinic acid derivatives

The syntheses of new γ-ethoxycarbonyl- and α-amino-alkyl hydroxymethylphosphinic acid derivatives are described. These compounds were conveniently prepared by Michael addition or Kabachnik–Fields reaction of an original precursor, ethyl benzyloxymethyl hydrogenophosphinate, respectively to α,β-unsaturated esters using a basic activation or to imines. Selective deprotection of the alcohol function was achieved by hydrogenolysis on Pd/C, whereas lithium bromide was used to selectively cleave the phosphinate ester group. Acidic hydrolysis readily gave the free hydroxymethylphosphinic acids.