A flexible approach to construct three contiguous chiral centers of sphingolipids, and asymmetric synthesis of d-ribo-phytosphingosine and its derivatives

An efficient approach to build the three contiguous stereogenic centers of sphingosine unit starting from cheap glutamic acid is described. The key step of this approach is the SmI2-mediated cross-coupling of chiral N-tert-butanesulfinyl imine 11 with sterically hindered aliphatic aldehyde 9 or 21 to construct hydroxymethyl β-amino alcohol 10 or 22 in high diastereoselectivity (>99%, de). The utility of this flexible method has been demonstrated in the synthesis of d-ribo-phytosphingosine 1, its two derivatives 18 and 29. Moreover, a practicable synthetic route for synthesis of various sphingolipids, ceramides, α-galactosylceramides and their derivatives is also described.