New approach to the enantiomerically pure 1,2,3-trihydroxypropylphosphonates

The replacement of 2,3-O-cyclohexylidene-d-glyceraldehyde with (2R,5R,6R)-5,6-dimethoxy-5,6-dimethyl-1,4-dioxane-2-carbaldehyde (Ley's aldehyde) has led to significant improvements in the isolation of both diastereoisomers of the respective 2,3-O-BDA 1,2,3-trihydroxypropylphosphonates. The triethylamine-catalysed addition of dialkyl phosphites and lithium diethyl phosphonate gave the products in moderate (ca. 1:2) diastereoselectivity while the application of diethyl trimethylsilyl phosphite afforded a 1:9 mixture of diethyl (R)- and (S)-hydroxy-[(2R,5R,6R)-5,6-dimethoxy-5,6-dimethyl-1,4-dioxan-2-yl]methylphosphonates.