Addition of Dialkyl Phosphites and Dialkyl Trimethylsilyl Phosphites to 2‐(Benzyloxy)propanal – Preparation of all Four Stereoisomeric (1,2‐Dihydroxy‐[1‐2H1]propyl)phosphonic Acids from Chiral LactatesDimethyl trimethylsilyl phosphite, diisopropyl trimethylsilyl phosphite, dimethyl phosphite, and diisopropyl phosphite were added to 2‐(benzyloxy)propanals4and6at different temperatures in THF and CH2Cl2. The ratio of diastereomers formed was highest for diisopropyl trimethylsilyl phosphite (erythro/threo3:1) and dropped to about 1:1 for diisopropyl phosphite. Starting from chiral lactates all four stereoisomeric diisopropyl (2‐benzyloxy‐1‐hydroxy‐[1‐2H1]phosphonates were prepared and deprotected. The (1,2‐dihydroxy‐[1‐2H1]propyl)phosphonic acids formed were purified as cyclohexylammonium salts. The relative configuration of phosphonic acid of (−)‐11was determined by comparison with the salt (1