New water-soluble isoxazole-linked 1,3,4-oxadiazole derivative with delocalized positive charge

Herein we present a synthesis and characterization of a new and unique low-weight heterocyclic compound 5-amino-2-(5-amino-3-methyl-1,2-oxazol-4-yl)-3-methyl-2,3-dihydro-1,3,4-oxadiazol-2-ylium bromide with the unusual electron charge delocalization owing the local positive charge at the carbon atom of oxadiazole moiety. X-ray single crystal of C7H10N5O2 center dot Br- showed the molecule crystalized in monoclinic, space group P2(1)/c. Both five membered rings are planar and twisted forming the ring motif with the counter ion where HMIDLINE HORIZONTAL ELLIPSISBr interactions are one of the dominant. The presented compound is characterized by high ionization efficiency in ESI-MS mode and undergoes dissociation within oxadiazole moiety under ESI-MS/MS conditions even under low collision energies. The presented compound is an interesting example of heterocyclic stable carbocation which may serve as a new lead structure.