Phosphonic acid analogs of GABA through reductive dealkylation of phosphonic diesters with lithium trialkylborohydrides

Lithium trialkylborohydrides were found to effect rapid monodealkylation of phosphonic diesters, and this reaction was applied to the synthesis of alkylphosphonic acid 2-aminoethyl esters [H2N(CH2)2OP(OH)R, 4], a little-explored class of analogs of the inhibitory neurotransmitter γ-aminobutyric acid (GABA). Compound 4a (R = Me) proved to be a potent antagonist at human ρ1 GABAC receptors (expressed in Xenopus laevis oocytes), with an IC50 of 11.1 μM, but is inactive at α1β2γ2 GABAA receptors.

Graphical abstractLithium trialkylborohydrides were found to mono-dealkylate dialkylphosphonates rapidly (rate of cleavage Me, Bn > 1°). The reaction was applied to the synthesis of a new GABAC antagonist, 2-aminoethyl methylphosphonate (4a).Figure optionsDownload full-size imageDownload as PowerPoint slide