Click Chemistry

1. ClickChemistry Reporter：Cheng-Yu Chung Date:2013/12/27 Advisor：Prof.Wen-Chang Chen

2. Outline • Introduction • Experimantal Copper-catalyzed alkyne-azidecycloaddition Cu-free alkyne-azidecycloaddition Diels–Alder reaction Thiol–enereaction • Applications • Conclusions

3. Introduction

4. (The Nobel Prize in Chemistry 2001 ) What is “Click” chemistry？ Defination: We endeavor to generate substances by joining small units together with heteroatom links (C-X-C). The goal is to develop an expanding set of powerful, selective, and modular“blocks” that work reliably in both small- and large-scale applications. It is important to recognize that click reactions achieve their required characteristics by having a high thermodynamic driving force, usually greater than 20 kcal/mol Objective: K. Barry. Sharpless 1.We present here synthetic methods for drug discovery that adhere to one rule: all searches must be restricted to molecules that are easy to make. 2.The reaction must be modular, wide in scope, give very high yields, generate only inoffensive byproducts that can be removed by nonchromatographicmethods, and be stereospecific. 3.Such processes proceed rapidly to completion and also tend to be highly selective for a single product Angew. Chem. Int. Ed. 2001, 40, 2004 - 2021

5. Outline • Introduction • Experimantal Copper-catalyzed alkyne-azidecycloaddition Cu-free alkyne-azidecycloaddition Diels–Alder reaction Thiol–enereaction • Applications • Conclusions

6. Selection of reactions that best meet the criteria for a “click” reaction Cu(I)-catalyzed Huisgen 1,3-dipolar cycloaddition of alkynes and azides strain-promoted cycloaddition of alkynes and azides Diels–Alder reaction thiol–ene reaction. G.K. Such et al. / Progress in Polymer Science 37 (2012) 985–1003

7. Copper-catalyzed alkyne-azidecycloaddition Mechanism of Cu(I)-Catalyzed Alkyne–Azide Coupling Advantage: 1.CuAAC proceeds efficiently at room temperature 2. CuAAC proceeds in many protic and a proticsolvents,including water 3.unaffected by most inorganic and organic functional groups. 4.good exo-endo selectivity Traditional products of thermal 1,3-cycloaddition Disadvantage: CuAAC is the need for Cu(I) and the associated potential toxicity. Proposed outline of species involved CuAAC Eur. J. Org. Chem. 2006, 51–68

8. Cu-free alkyne-azidecycloaddition Bioorthogonal reaction of cyclooctyne probes with azide-labeled biomolecules allows their interrogation in cell-based systems. Cells are treated with azide-functionalized metabolic substrates. The azides are then detected with a cyclooctyne-functionalized probe. (B) Cyclooctynesdesigned for fast Cu-free click chemistry (1-3) and reactivity studies (4). The R-group denotes the location for linkage to a probe moiety.

9. Cu-free alkyne-azidecycloaddition Synthesis strategies  Scheme 1. Retrosynthesis of BARAC (1) Scheme 2. Synthesis of BARAC (15)

10. Cu-free alkyne-azidecycloaddition Figure 2. BARAC-probe conjugates label live cells with superior sensitivity compared to DIFO and DIBO reagents. (A) Structures of BARAC-biotin (16) and BARAC-Fluor (17). (B C) Flow cytometry plots of live cell labeling with BARAC-biotin. Jurkat cells were incubated with ( Az) or without ( Az) 25 µMAc4ManNAz for 3 days. The cells were labeled with 1 µM cyclooctyne-biotin for various times and then treated with FITC-avidin. Cyclooctyne- biotin probes used were DIBO-biotin, BARAC-biotin, or DIFO-biotin. The degree of labeling was quantified by flow cytometry. The level of fluorescence is reported in mean fluorescence intensity (MFI, arbitrary unit). Error bars represent the standard deviation of three replicate experiments. (B) Comparison of the efficiencies of labeling of different cyclooctyne reagents after 1 h. (C) Time-dependent labeling of cyclooctyne-biotin probes. MFI reported as difference between signal of cells Az and signal of cells Az.

11. Cu-free alkyne-azidecycloaddition Imaging of azide-labeled glycans on live cells using BARAC-Fluor J. AM. CHEM. SOC. 2010, 132, 3688–3690

12. Diels–Alder reaction Advantage: 1.DA cycloaddition offer a reagent -free ‘click’ reaction 2.design of thermoreversiblematerials 3.highly sensitive to the temperature 4.good exo-endo selectivity Maleimide functional group: An ideal ‘click’ substrate. Disadvantage: Temperature too high lead to lower yields (the competing retro Diels–Alder reaction) Diels–Alder/retro Diels–Alder reaction sequence. Macromol. Chem. Phys. 2010, 211, 1417–1425

13. Diels–Alder reaction Molecular design self healing crosslinked materials thermoreversible symmetrical dendrimers thermoresponsive segment-block dendrimers Dendron graft polymers via the rDA/DA sequence

14. Thiol–ene reaction General thiol–ene coupling : (Michael addition) ==>a single thiolreacts with a single ene to yield the product. thiol–ene polymerization processes a) alkyl thiols(b) multifunctional thiols Typical multifunctional enes Advantage: highly efficient, simple to execute with no side products and proceeding rapidly to high yield. Applications:highperformance protective polymer networks to processes that are important in the optical, biomedical, sensing, and bioorganic modification fields. Angew. Chem. Int. Ed. 2010, 49, 1540 – 1573

15. Thiol–enereaction-Syntheticmethod Synthetic method for 48-functional polyoldendrimerusingsequential thiol–ene radical and esterification reactions. etc. Thiol–enephotoinitiated free-radical reaction of a 48-functional enedendrimerwithselective monofunctionalthiols

16. Polymeric carrier systems involving “Click Chemistry” G.K. Such et al. / Progress in Polymer Science 37 (2012) 985–1003

17. Outline • Introduction • Experimantal Copper-catalyzed alkyne-azidecycloaddition Cu-free alkyne-azidecycloaddition Diels–Alder reaction Thiol–enereaction • Applications • Conclusions

18. Drug delivery ACS Nano, 2010, 4 (7), pp 4211–4219

19. Outline • Introduction • Experimantal Copper-catalyzed alkyne-azidecycloaddition Cu-free alkyne-azidecycloaddition Diels–Alder reaction Thiol–enereaction • Applications • Conclusions

20. Conclusions • There is now a well- studied set of reactions which satisfy most click criteria and thus the choice of the appropriate reaction for a specific set of conditions is straightforward. • Click chemistry offers a powerful toolbox for material scientists to design the next generation of materials with targeted response to the environment. • This is particularly true in the field of biomedicine where knowledge on the interactions between synthetic delivery systems both in vitro and in vivo is rapidly expanding.