Cyclooctynes for SPAAC

Pfizer compound category

Among the most well-known bioorthogonal transformations is the Strain-Promoted Azide–Alkyne Cycloaddition (SPAAC). One component of the reaction, alkyl azide, is a common class of compounds that are commercially available or can be synthesized through simple chemical transformations. On the other hand, alkynes need to be strained to react at physiological temperatures without the use of a catalyst. Cyclooctynes and hetero-cycloalkynes are the smallest cyclic alkynes stable enough for practical applications. Yet, their inherent ring strain is what really sets them apart, enabling [3+2] cycloadditions with azides and other dipoles (like nitrile oxides, nitrile imines, and nitrones) without the need for catalysis, even at biological temperatures.