Method for the synthesis of phosphinic acids from hypophosphites V. The synthesis of pseudo-α,α-dipeptides

Summary.

The method for the synthesis of 2-substituted 2-hydroxycarbonylethyl-1-aminoalkylphosphinic acids (I) (pseudo-α,α-dipeptides) from ammonium and potassium hypophosphites (II) is described. The proposed route to the synthesis of pseudo-α,α-dipeptides consists in addition hypophosphite to acrylic compounds and formation of the first phosphorus–carbon bond with following addition of aminoacid fragment and formation of the second phosphorus–carbon bond. The key intermediates of the synthesis – phosphonous acids (III) and their silylic esters (IV) were obtained at the first stage of the process as the result of the addition of the bis(trimethylsilyl)hypophosphite in situ to suitably substituted acrylates. The modificated procedure for the Kabachnik-Fields reaction of 2-substituted 2-alkoxycarbonylethyl phosphonous acids (III), acetamide, benzaldehyde in acetic anhydride with following hydrolysis results in 2-substituted 2-hydroxycarbonylethyl-α-aminobenzyl phosphinic acids (Ia–c) (pseudo-phenylglycylpeptides). Bis(trimethylsilyl) 2-substituted 2-alkoxycarbonylethylphosphonites (IV) in situ were added to N-tritylmethanimine and following alcoholysis and acid hydrolysis of addition products gave 2-substituted 2-hydroxycarbonylethyl-aminomethylphosphinic acids (Id–f) (pseudo-glycylpeptides).