SM(d18:2/22:0) 603.450 603.835 C45H91N2O6P CHEBI:136388 N-docosanoyl-sphingadienine-1-phosphocholine [C@]([C@@](/C=C/*)(O)[H])(NC(=O)CCCCCCCCCCCCCCCCCCCCC)([H])COP(OCC[N+](C)(C)C)([O-])=O chebi_ontology sphingomyelin 40:2