Syntheses of novel phosphorus heterocycles containing α-amino or α-hydroxyphosphonic or phosphinic acids motifs are developed. 2,3-dihydro-1,3-oxaphospholes (1) and 1,4,2-oxazaphosphinanes (2) exhibit a reactive part, respectively the enolether moiety and the P–H bond, which allows various structural modifications: (i) for 1a, by introduction of amino substituents, (ii) for 2a, by hydroxy- or aminoalkylation