is deprotonated form of is enantiomer of sphingosine (2R,3S)-2-aminooctadec-4-ene-1,3-diol L-erythro-sphingosine A (2<i>R</i>,3<i>S</i>)-2-aminooctadec-4-ene-1,3-diol in which the double bond has <i>E</i> geochemistry. L-erythro-sphingosine(1+)