Nature-Inspired Bioorthogonal Reaction: Development of β-Caryophyllene as a Chemical Reporter in Tetrazine Ligation

Abstract

A nature-inspired bioorthogonal reaction has been developed, hinging on an inverse-electron-demand Diels-Alder reaction of tetrazine with β-caryophyllene. Readily accessible from the cheap starting material through a scalable synthesis, the newly developed β-caryophyllene chemical reporter displays appealing reaction kinetics and excellent biocompatibility, which renders it applicable to both in vitro protein labeling and live cell imaging. Moreover, it can be used orthogonally to the strain-promoted alkyne-azide cycloaddition for dual protein labeling. This work not only provides an alternative to the existing bioorthogonal reaction toolbox, but also opens a new avenue to utilize naturally occurring scaffolds as bioorthogonal chemical reporters.

Pro‐aromaticity Enabled Dealkenylative Functionalizations via Photo‐Excitation and Oxidation

“…Another interesting substrate was (À )-β-caryophyllene (26 c) containing two alkenes. The preference of the endocyclic trisubstituted alkene to participate IEDDA over the 1,1-disubstituted alkene has been established, [29] including in the reaction with tetrazine, [30] which could be rationalized by the ring strain of trans-cyclononene. The same regioselectivity was observed in the reaction of 26 c and tetrazine 2, and the cleavage followed by Minisci-type alkylation gave product 27 e. The relatively low yield could be attributed to other side reactions due to the presence of weak allylic CÀ H bonds in (À )β-caryophyllene.…”

Highly Strained Unsaturated Carbocycles

“…[105] This particular natural product has been used in bioorthogonal reactions. [106] Wu and co-workers reported the use of -Caryophyllene 103 in an iEDDA reaction with tetrazines such as 70 (Scheme 36), leading to constructs like 104, which could be applied to in vitro protein labelling and live cell imaging.…”

Development of Biocompatible Ene-Ligation Enabled by Prenyl-Based β-Caryophyllene with Triazoline/Selectfluor under Physiological Conditions

“…Biocompatible ligation is a chemical process that ensures covalent ligation under mild physiological conditions. − The IEDDA reaction has been widely utilized to ligate the molecule-of-interest (MOI) in the past decades because of its good biocompatibility, high selectivity, among other properties. , However, challenges remain in this field such as complicated synthetic procedures of one of the key coupling partners, trans -cyclooctene, and its analogue, limiting its applications. Thus, a readily available coupling partner with excellent kinetics and selectivity, that is, a trans -cyclooctene-like natural molecule is needed. Notably, ready availability and inert balance between stability and reactivity are crucial for coupling partners used in biocompatible ligations.…”

“…4,5 However, challenges remain in this field such as complicated synthetic procedures of one of the key coupling partners, trans-cyclooctene, and its analogue, limiting its applications. Thus, a readily available coupling partner with excellent kinetics and selectivity, that is, a trans-cyclooctenelike natural molecule 6 is needed. Notably, ready availability and inert balance between stability and reactivity are crucial for coupling partners used in biocompatible ligations.…”