Amino group, sterically hindered

The unsubstituted phthalic acid hydrazide and several nonaromatic cyclic hydrazides such as maleic acid hydrazide or succinic acid hydrazide are either nonchemiluminescent or show extremely weak CL. However, the 6-amino isomer of luminol, which is called isoluminol, is chemiluminescent to about the same extent as is luminol. Isoluminol has been used in many chemiluminescent studies, and because the amino group is less sterically hindered than that of luminol, it is probably derivatized for chemiluminescent labeling far more often than is luminol (Fig. 3). 

Sterically hindered amino substituents or amino substituents with electron-with-drawing groups in the 3-position of the sydnonimine ring, as in Marsidomine 88, C89-4095 89 or C4144 90, have little impact on the stability of the heterocyclic system toward ring opening, but are able to slow down the process of oxidative NO-release from the nitroso intermediates [107]. 

Acylation of the Sterically Hindered Secondary a-Amino Group Attached to the BAL-Anchor... 

M. Cerny, H. Vecerkova, I. Cerny, and J. Pacak, Preparation of 2-amino-l,6-anhydro-2-deoxy-jS-D-mannopyranose by intramolecular substitution of the tosyloxy group in sterically hindered position of l,6-anhydro-2-0-p-tolylsulfonyl-/6-D-glucopyranose, Collect. Czech. Chem. Commun., 45 (1980) 1837-1844. 

The differential reactivity of the sterically hindered and unhindered isocyanate groups of tolylene-2,4-diisocyanate facilitates the stepwise conjugation of hapten (R) and protein (P) amino groups (Fig. 3, Rn 7). jd.jj -Difluoro-m,m -dinitrobenzene (DFDNB) reacts with numerous functionalities including primary and secondary amines, imidazoles, and phenols to yield mixtures of conjugated materials (Fig. 3, Rn 8). This reaction is apparently harder to control than the diisocyanate reactions, but it is much more versatile. 

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