Compositions and methods for modular control of bioorthogonal ligation

Abstract
The present invention provides a compound having the structure- Formula (I) wherein R1 is H or a protecting group; R2 and R3 are each independently H, halo, C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C1-C6 alkyl-C(O)NHR6, C1-C6 alkyl-C(O)OR6, wherein R6 is H, C1-C6 alkyl, C2-C6 alkenyl or C2-C6 alkynyl, or R2 and R3 combine to form a 3-7 membered cycloalkyl, heterocycloalkyl, aryl or heteroaryl ring; and R4 and R5 are each independently halo.