The synthesis of two isosteric phosphonate analogs of the M6P recognition m
arker, present in the lysosomal enzyme structure, is described. The phospho
nate 1, a bioisosteric analog of the M6P was obtained via a multistep synth
esis using the trimethylsilyl protective group. Only this method allowed th
e obtention of the mannosylphosphonate 2, functionalized in the anomeric po
sition by a paraaminophenyl group which is commonly use to link proteins or
other substrates of biological interest.