Synthesis of sphingosines, 9. Synthesis of phytosphingosine derivatives

Reaction of the lithium acetylide prepared from bromooctene 2 with 2,4‐O‐benzylidene‐D‐threose (1) yielded the epimeric dodec‐5‐ynetetrol derivatives 3a, b. Reaction of the Grignard reagent of bromooctene 2 with 1 gave (E,Z)‐dodec‐5‐ene‐tetrol derivatives (E,Z)‐12a,b. From these precursors D‐ribo‐phytosphingosine derivatives 7b, (E)‐18, and (Z)‐18, respectively, were obtained. Also interesting anhydro derivatives, for instance 3,4‐epoxides 11a and (E)‐21, and 1,4‐anhydro phytosphingosine derivatives 9a, 10a, and (E)‐23, respectively, were synthesized. A very useful method is described for the assignment of the configuration at C‐4 of the 1,3‐O‐benzylidene‐1,2,3,4‐tetrol derivatives 3a, 3b, (E,Z)‐12a, and (E,Z)‐12b by means of NMR spectroscopy. magnified image