Novel immunomodulator FTY720 is phosphorylated in rats and humans to form a single stereoisomer.: Identification, chemical proof, and biological characterization of the biologically active species and its enantiomer

In vivo phosphorylation. of FTY720 (1) in rats and humans resulted exclusively in the biologically active (S)-configured enantiomer, which was proven by an ex vivo o-phthaldialdehyde derivatization protocol especially elaborated for phosphates of 1. Starting from the prochiral amino alcohol 1, racemic and enantiomerically pure phosphates of 1 were synthesized. Pure enantiomers were obtained after purification of a partially protected key intermediate on an enantioselective support. The absolute stereochemistry was determined by X-ray diffraction.