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

Outline  Introduction  Experimantal C opper-catalyzed alkyne-azide cycloaddition Cu-free alkyne-azide cycloaddition Diels–Alder reaction Thiol–ene reaction  Applications  Conclusions

Introduction

3.Such processes proceed rapidly to completion and also tend to be highly selective for a single product 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 2.The reaction must be modular, wide in scope, give very high yields, generate only inoffensive byproducts that can be removed by nonchromatographic methods, and be stereospecific. 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. Angew. Chem. Int. Ed. 2001, 40, What is “Click” chemistry ？ (The Nobel Prize in Chemistry 2001 ) Objective: K. Barry. Sharpless

Outline  Introduction  Experimantal C opper-catalyzed alkyne-azide cycloaddition Cu-free alkyne-azide cycloaddition Diels–Alder reaction Thiol–ene reaction  Applications  Conclusions

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

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

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

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

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. Cu-free alkyne-azide cycloaddition

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

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

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

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

Thiol–ene reaction-Synthetic method etc. Thiol–ene photoinitiated free-radical reaction of a 48-functional ene dendrimer with selective monofunctional thiols Synthetic method for 48-functional polyol dendrimer using sequential thiol–ene radical and esterification reactions.

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

Outline  Introduction  Experimantal C opper-catalyzed alkyne-azide cycloaddition Cu-free alkyne-azide cycloaddition Diels–Alder reaction Thiol–ene reaction  Applications  Conclusions

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

Outline  Introduction  Experimantal C opper-catalyzed alkyne-azide cycloaddition Cu-free alkyne-azide cycloaddition Diels–Alder reaction Thiol–ene reaction  Applications  Conclusions

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 speci fi c 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 fi eld of biomedicine where knowledge on the interactions between synthetic delivery systems both in vitro and in vivo is rapidly expanding.