Journal of Lipid Research (Feb 1978)
Total synthesis of stereospecific sphingosine and ceramide
Abstract
A small-scale synthesis of the four sphingosine stereoisomers (D-erythro, L-erythro, D-threo, and L-threo) and lignoceroyl D- and L-erythro-sphingosines, which is suitable for synthesis of tritium-labeled compounds, is described. Ethyl DL-erythro-2-acetamino-3-hydroxy-4t-octadecenoate was esterified with L(+)-acetylmandeloyl chloride and the two diastereomers obtained were separated from each other by thin-layer or column chromatography. Each diastereomer was subjected to ethanolysis to obtain ethyl D- or L-erythro-2-amino-3-hydroxy-4t-octadecenoate which was then reduced with LiAlH4 or NaBH4 to yield D- or L-erythro-sphingosine. D-erythro-[1-3H]Sphingosine with high specific activity was prepared by using LiAl3H4 in the last step. D- and L-threo-sphingosines were synthesized from ethyl DL-threo-2-acetamino-3-hydroxy-4t-octadecenoate by using a similar procedure.Ceramide (lignoceroyl sphingosine) was prepared either by acylating sphingosine or by the following new method. Ethyl DL-erythro-2-amino-3-hydroxy-4t-octadecenoate was converted to the N-lignoceroyl derivative and esterified with L(+)-acetylmandeloyl chloride. The two diastereomers obtained were separated and each isomer was treated with a catalytic amount of sodium ethoxide. One of the products, ethyl D-erythro-2-lignoceroylamino-3-hydroxy-4t-octadecenoate, was reduced with NaBH4 to yield ceramide. N-palmitoyl DL-erythro-sphingosine was also prepared using an identical procedure. N-lignoceroyl D-erythro-[1-3H]sphingosine was prepared by NaB3H4 reduction of the corresponding amide ester. A doubly labeled ceramide, [1-14C]lignoceroyl [1-3H]sphingosine, containing high specific activity, was prepared by mixing the above N-lignoceroyl D-erythro-[1-3H]sphingosine and N-[1-14C]lignoceroyl D-erythro-sphingosine. The conversion of the doubly labeled ceramide to 3-keto derivative is also described.