Use of heterocycles as chiral ligands and auxiliaries in asymmetric syntheses of sphingosine, sphingofungins B and F

Article abstract of DOI:10.1016/S0040-4020(98)00484-0

D-erythro-Sphingosine and its derivatives (dihydrosphingosine, cissphingosine, etc.), sphingofungins B and F have been synthesized from simple achiral compounds using heterocyclic compounds as key chiral ligands and auxiliaries. 5-Benzyloxy-4-ethynyl-2,2-dimethyl-1,3-dioxane (5 or 5- ent), a key intermediate for the synthesis of sphingosine family, was prepared from 1-trimethylsilylpropinal and ketene silyl acetal 4 using a Sn(OTf)₂-chiral ligand 1 or 1-ent-catalyzed asymmetric aldol reaction. Sphingosine and its derivatives were readily prepared from 5 according to standard transformation. The chiral hydrophobic side chain (6) of sphingofungin B was synthesized using a catalytic asymmetric aldol reaction using chiral ligand 1-ent. Another key step in the total synthesis of sphingofungin B was a condensation of chiral aldehyde 7 and chiral heterocycle 2. Similarly, the reaction of chiral aldehyde 8 with heterocycle 3 was a key step for the synthesis of sphingofungin F. Highly diastereoselective reactions proceeded smoothly in both cases to afford the corresponding adducts in high yields.