Diazo- and azido-functionalized glutaraldehydes as cross-linking reagents and potential fixatives for electron microscopy.

The synthesis of diazo and perfluorophenyl azide (PFPA) functionalized glutaraldehydes 7 and 13a-d as new cross-linking reagents for bioconjugation and potential fixatives for electron microscopy is reported. A key step is the generation of the 1,5-dialdehyde structures by oxidative cleavage of the corresponding cyclopentene epoxide using HIO4 in aqueous tetrahydrofuran. A model reaction between 3-substituted glutaraldehyde 14 and 6-aminohexanoic acid resulted in the formation of pyridinium ion containing products with UV spectra comparable to those observed with glutaraldehyde itself. Thus modification of glutaraldehyde in the 3-position most probably did not significantly change its reactivity with amines under chemical-fixation conditions. Fixation of red blood cells by 7 demonstrates that as a fixative, 7 is comparable to glutaraldehyde.