Synthesis of water‐soluble near‐infrared cyanine dyes functionalized with [(succinimido)oxy]carbonyl group

Two hetamethine cyanine dyes suitable for labeling of biomolecules at a primary amino group with a near‐infrared chromophore/fluorophore (λ max /(λ em = 800/830 nm and 837/864 nm) have been synthesized from readily available starting materials. Despite the high molecular complexity of intermediate and final products, all these compounds have been obtained in an analytically pure form by using crystallization only.