Stereochemistry determination of the Fom3 product. (a) Methyl signals in 1H NMR spectra (D2O, 600 MHz) of standards of (2R)-2-HPP-CMP, (2S)-2-HPP-CMP, and a mixture of (2R)- and (2S)-2-HPP-CMP. (b) 31P NMR spectra (D2O, 600 MHz) of the products after reaction of FomD and Fom4 with a mixture of (2R)- and (2S)-2-HPP-CMP standards (top) and with 2-HPP-CMP produced by Fom3 (bottom), demonstrating that only fosfomycin is formed from the Fom3 product and not 2-OPP.