Bioorthogonal Removal of 3-Isocyanopropyl Groups Enables the Controlled Release of Fluorophores and Drugs in Vivo

Abstract

Dissociative bioorthogonal reactions allow for chemically controlling the release of bioactive agents and reporter probes. Here we describe 3-isocyanopropyl substituents as masking groups that can be effectively removed in biological systems. 3-Isocyanopropyl derivatives react with tetrazines to afford 3-oxopropyl groups that eliminate diverse functionalities. The study shows that the reaction is rapid and can liberate phenols and amines near-quantitatively under physiological conditions. The reaction is compatible with living organisms as demonstrated by the release of a resorufin fluorophore and a mexiletine drug in zebrafish embryos implanted with tetrazine-modified beads. The combined benefits of synthetic ease, rapid kinetics, diversity of leaving groups, high release yields, and structural compactness, make 3-isocyanopropyl derivatives attractive chemical caging moieties for uses in chemical biology and drug delivery.

Innovative Linker Strategies for Tumor‐Targeted Drug Conjugates

“…In addition, the same group demonstrated that a pyrazole–imine intermediate (compound 79 in Scheme C) formed by tetrazine [1+4] cycloaddition with 3‐isocyanopropyl (ICP) tags ( 76 ) can undergo efficient payload release through imine hydrolysis and β‐elimination in aldehyde 80 . The feasibility of this “click and release” strategy was confirmed by the efficient activation of phenolic and carbamate drugs in live zebrafish …”

Dissociative Bioorthogonal Reactions

“…Based on reports that 3‐oxopropyl groups liberated leaving groups by β‐elimination, we designed 3‐isocyanopropyl moieties that react with tetrazines to release payloads under physiological conditions (Scheme ). Effective release of phenols and amines from 3‐isocyanopropyl derivatives triggered by tetrazines was experimentally shown . 3‐Isocyanopropyl groups reacted with 3,6‐di(pyridin‐2‐yl)‐1,2,4,5‐tetrazine at rates of up to 4.0 m −1 s −1 in PBS/DMSO (90:10) at 37 °C.…”

“…Albumin catalyzed the β‐elimination, and the release step went to completion in minutes. Isocyanopropyl‐modified molecules were easy to synthesize from inexpensive starting materials . Moreover, imaging and drug‐delivery experiments in zebrafish embryos demonstrated that the reaction is compatible with living systems.…”

“…Effective releaseo fp henols and amines from 3-isocyanopropyl derivatives triggered by tetrazines was experimentally shown. [61] 3-Isocyanopropyl groups reactedw ith 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine at rates of up to 4.0 m À1 s À1 in PBS/DMSO (90:10) at 37 8C. Albumin catalyzed the b-elimination, [62] and the releases tep went to completion in minutes.…”

“…Isocyanopropyl-modifiedm olecules were easy to synthesize from inexpensive starting materials. [61] Moreover, imaging andd rug-delivery experiments in zebrafish embryos demonstrated that the reactioni sc ompatible with living systems. These preliminarys tudies indicated the potential of implementing the structurally compacti socyano group in various chemicalbiology and therapeutics applications.…”