The above findings are all valid reasons to suggest that both carboxyl ester and hydrazone moieties in NInC esters are thermodynamically similar in nature, and even though they, in point of fact, possess different kinetics e.g. as we saw above NInC 12 was the kinetic product, and an intermediate in the course of hydrolytic decomposition of ester 18, the activation barriers between 12 and its ensuing decomposed products are relatively insufficient to resist its further break down. In the face of the aforementioned difficulties in keeping the cleavable linker i.e. the hydrazone moiety intact whilst hydrolysing the carboxyl ester protecting group (PG) in the NInCs, other too compelling not to miss PGs including, but not limited to p-methoxybenzyl and trimethylsilylethoxymethyl PGs were also examined, and none were able to deliver the desired NInCs (ESI S4-7 †). Hardly surprisingly, attempts at coupling the naked bromo-InC 20 to 1 were equally futile.