Synthesis of 7-aza- and 7-thiasphingosines, and evaluation of their interaction with sphingosine kinases and with T-cells.

The synthesis of 7-oxasphingosine (3) and 7-oxaceramide (4) was improved by starting from the 4-methoxybenzyl-protected d-galactal 9. The sphingosine analogues 5-7 and 24 were synthesized via the azido alcohol 13. The 7-thiasphingosine 5 is a poorer substrate for both isoforms of sphingosine kinase (SPHK) than sphingosine, but showed a slight preference for SPHK2. The sulfone 6 and the 7-aza compounds 7 and 24 were not phosphorylated by either SPHK1 or SPHK2, and none of 5-7 and 24 activated invariant natural killer T (iNKT) cell clones when presented by human CD1d-transfected antigen-presenting cells (APC) or by plate-bound human CD1d. Only 7 and 24 associated with plate-bound recombinant CD1d prevented stimulation of iNKT cells by alpha-galactosylceramide (alpha-GalCer).