Chemoenzymatic synthesis of phosphocarnitine enantiomers

Racemic phosphocarnitine 3 has been synthesized starting from diethyl 3-chloro-2-oxopropanephosphonate 4 in three steps involving reduction of 4 to the corresponding 2-hydroxyphosphonate 5, conversion of the latter to phosphonic acid 6, and final reaction with trimethylamine, affording the trimethylammonium salt of 3. Baker's yeast reduction of 4 and enzymatic kinetic resolution of (+/-)-5 afforded the enantiomerically pure precursors of phosphocarnitine, (R)-(+)-5 and (S)-(-)-5, which were converted to (S)-(-)- and (R)-(+)-phosphocarnitine 3, respectively.