A Concise and First Synthesis of α‐Aminophosphinates with Two Stereogenic Atoms Leading to Optically Pure α‐Amino‐ H ‐phosphinic Acids

One stone, two birds: Nucleophilic addition of ethyl diethoxymethylphosphinate to (S)-(tert-butanesulfinyl)methylphenylketimine in the presence of Rb2CO3 in CH2Cl2 at room temperature leads to the unprecedented isolation of two enantioenriched α-aminophosphinates (>99 % ee), both with R configuration on the carbonyl atom, but with different configuration on the phosphorus atom (see scheme). Subsequent hydrolysis of the diastereoproducts in 4 n HCl, for the first time, leads to optically pure α-amino-H-phosphinic acids.