trans-Cyclooctene (TCO) derivatives and 1,2,4,5-tetrazine (Tz) derivatives undergo highly selective and rapid reactions via the inverse electron-demand Diels–Alder (IEDDA) reaction. Compared to alkyne-azide click reactions (CuAAC, SPAAC), the IEDDA reaction proceeds faster, requires no metal catalysts, and exhibits excellent bioorthogonality.

Carbamate-modified TCO* (2-TCO) and certain Tz derivatives are known to release amine compounds following the IEDDA reaction, in what is called a "click-to-release" process. This click-to-release strategy has been applied to prodrug development and protein caging systems.

This reaction enables the controlled release of molecules at desired times and locations without the use of catalysts, owing to its highly selective and ultrafast click reactivity under physiological conditions. Importantly, this is a clean reaction, producing only N₂ and CO₂ as byproducts.

For preparation of TCO*-payloads, the axial isomer of TCO* is preferable. It has been reported that the axial isomer reacts via IEDDA approximately 150 times faster than the equatorial isomer.

In the release process following the IEDDA reaction, the substituents on the tetrazine (Tz) play a critical role. Among tetrazine derivatives, Me-Tz (3-methyl-1,2,4,5-tetrazine) is widely used. While H-Tz (1,2,4,5-tetrazine) undergoes IEDDA faster than Me-Tz, it is known to exhibit significantly reduced release efficiency afterward.

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Advantages

• High-purity isomers of TCO* (axial and equatorial) are individually isolated and in our product lineup.
• TCO*-payloads can be synthesized from the p-nitrophenylcarbonate ester of TCO* axial isomer (Product No.T4218)
• Various Me-Tz derivatives are available as our products, allowing you to select the most suitable reagent for your experiments.

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Products

TCO* Derivative

Me-Tz Derivatives

for Amino Groups

for Carboxy Groups

for Azido Groups

for Alkynes

for Avidins

for Others

T4218

TCO*-NPC axial isomer

T4219

TCO*-NPC equatorial isomer

M3494

Methyltetrazine-NHS Ester

D6331

Methyltetrazine-amido-PEG3-NHS Ester

M3468

Methyltetrazine-PEG4-NHS Ester

M3558

[4-(6-Methyl-1,2,4,5-tetrazin-3-yl)phenyl]methanamine Hydrochloride

A3721

Methyltetrazine-amido-PEG3-Amine Hydrochloride

M3767

Methyltetrazine-amido-PEG3-Alkyne

M3769

Methyltetrazine-amido-PEG3-DBCO

A3697

Methyltetrazine-amido-PEG3-Azide

M3768

Methyltetrazine-amido-PEG3-Biotin

M3469

[4-(6-Methyl-1,2,4,5-tetrazin-3-yl]phenyl)methanol

B6382

3-[4-(Bromomethyl)phenyl]-6-methyl-1,2,4,5-tetrazine

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Related Product Spotlight Pages

• TCO (trans--cyclooctene) Derivatives: The Fastest Click Reaction Reagents
• Hetero-bifunctional Crosslinkers Containing Tetrazine which Selectively Reacts with Strained C-C Multiple Bonds

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References

• 1) Inverse electron demand Diels–Alder reactions in chemical biology
  • B. L. Oliveira, Z. Guo, G. J. L. Bernardes, Nature 2017, 46, 4895.
• 2) IEDDA: An Attractive Bioorthogonal Reaction for Biomedical Applications
  • M. Handula, K. T. Chen, Y. Seimbille, Molecules 2021, 26, 4640.
• 3) Bioorthogonal micellar nanoreactors for prodrug cancer therapy using an inverse-electron-demand Diels–Alder reaction
  • F. Suehiro, S. Fujii, T. Nishimura, Chem. Commun. 2022, 58, 7026.
• 4) Toward Realization of Bioorthogonal Chemistry in the Clinic
  • K. E. de Roode, R. Rossin, M. S, Robillard, Top. Curr. Chem. 2025, 383, 12.

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