A convenient diastereoselective synthesis of d-erythro- and l-threo-sphingosine derivatives is described. l-Serine-derived aldehyde (Garner's aldehyde) (2) was treated with 1-alkenyl-zirconocene chlorides (3) in the presence of ZnBr 2 in THF to give the natural erythro-(anti-) isomers with high diastereoselectivity (anti/syn=12-20:1). In contrast, reaction of 2 with 1-alkenyl-ethyl-zinc, prepared from 3 and Et 2 Zn, in CH 2 Cl 2 gave the unnatural threo-(syn-) isomers predominantly (anti/syn=1:12-15).