A Chemoenzymatic Access to d- and l-Sphingosines Employing Hydroxynitrile Lyases

A chemoenzymatic access to d- or l-sphingosines is presented comprising of a total synthesis of the l-threo-isomer and formal syntheses of the other three isomers. Key to the development of a general synthetic strategy has been the use of enantiocomplementary hydroxynitrile lyases (Hnls) to yield an enantiomeric pair of starting materials. The (S)-Hnl from Hevea brasiliensis has been used to prepare l-threo-sphingosine in 14 steps and an overall 12% yield. Application of the (R)-Hnl from Prunus amygdalus formally allows synthesis of d-threo- and d-erythro-sphingosines.