Chiral Phosphine Ligands from Amino Acids. II. A Facile Synthesis of Phosphinoserines by Nucleophilic Phosphination Reactions – X‐Ray Structure Analyses of Ar2P–CH2–CH(NHBOC)(COOMe) (Ar = Ph,m‐xylyl)

Phosphino derivatives of serine R₂P–CH₂–CH(NHBOC)(COOMe) ( 2 a – 2 d ) have been obtained in high yield by nucleophilic phosphination of N‐(tert.butoxycarbonyl)‐3‐iodo‐L‐alanine methylester with secondary phosphines R₂PH (R = Ph, 2‐tolyl, 3,5‐xylyl, cyclohexyl) in DMF using potassium carbonate as the base. Deprotection of 2 b with HCl affords the amino acid ester hydrochloride [2‐Tol₂P–CH₂–CH(NH₃)(COOMe)]⁺Cl^– ( 3 a ). The X‐ray structures of 2 a (space group P2₁/n) and 2 c (space group P 1) have been determined. The two enantiomers of 2 a or 2 c are interconnected by N–H…O hydrogen bridges forming dimers in the solid state.