Synthesis of P,N-Heterocycles from ω-Amino-H-Phosphinates: Conformationally Restricted α-Amino Acid Analogs

P,N-Heterocycles (3-hydroxy-1,3-azaphospholane and 3-hydroxy-1, 3-azaphosphorinane-3-oxide) are synthesized in moderate yield from readily available omega-amino-H-phosphinates and aldehydes or ketones via an intramolecular Kabachnik-Fields reaction. The products are conformationally restricted phosphinic analogs of alpha-amino acids. The multigram-scale syntheses of the H2N(CH2)(n)PO2H2 phosphinic precursors (n = 1, 2, 3) and some derivatives are also described.