In situ Click chemistry
Mgr. Juraj Dobiaš
KOCH, PRIF UK
What is Click Chemistry ?
joining molecules by an „ideal chemical reaction“
• fast, irreversible reaction, simple conditions
• starting materials are readily available, stable
(biocompatible)
• high yielding, high atom economy, wide application
• large thermodynamic driving force to give predictable
outcome
• easy work-up and product isolation
• preferably proceeding in water, insensitive to oxygen
• the best by some fusion reaction:
Synthesis of 1,2,3-triazoles
 Thermal Huisgen [3+2] cycloaddition
1950-70
Huisgen
• 80-120°C, 12-24h, both regioisomers ca 1/1
E#A= 24-26 kcal/mol
 Cu(I) catalyzed (CuSO4 / sodium L-ascorbate)
2002,
Fokin,
Sharpless
Melda
• only 1,4-regioisomer, high yield, rt,
t-BuOH / water environment
E#A= 15 kcal/mol (106 times faster than Huisgen r.)
N
R2
• mainly 1,5-regioisomer
N
R1
N
R1
1
4
N
 Ru catalyzed (Cp*RuCl(PPh3)2)
2005,
Fokin
Shrapless
N
N
1
4
5
R2
Click Chemistry Exploitation
• Material sciences (copolymers, functionalized surfaces, adhesives,
dendrimers, large macrocycles, ....)
• Bioorganic chemistry (biosensors, bioconjugates: tagging of
proteins, nucleotides or in situ whole organisms, SPAAC – no metal)
Drug development – Medicinal Chemistry
MMps inhibitors
8
Cu(I)
12
MMP7 selective, low mcM
inhibitors
Org. Lett. 8 2006 3821-24.
In Situ Click Chemistry (TDS)
target driven synthesis
TDS reduces the number of inactive compounds
Compensate the lack of precision in the predictive ability of in
Silico chemistry
In situ AA Click chemistry is completely biocompatible, uses
irreversible reaction to unite reagents inside the protein´s binding
pocket
Target will pick best fitting ligands from diverse sets of chemical
building blocks
Significant portion of the activation barrier is entropic (pieces
have to approach each other in precisely the right orientation),
pre-assembly of building blocks on the target active site can
accelerate cycloaddition.
DDT 9 2004 348.
Observation of the controlled assembly of preclick
components in the in situ click chemistry
generation of a chitinase inhibitor
• chitinase inhibitors fight against infectious and inflammatory
diseases – onchocerciasis.
• screening of over 10,000 extracts from soil microorganisms
2013 PNAS 110 15892-97
In situ click
Triazole komplex
3WD1
Captured transition state
• Alkene doesn’t cocrystalyze without azide even at high concentration – induced fit.
• Different pose of azide with and without alkene – double induced fit.
3WD2
3WD4
Summary
• Identified triazole inhibitor of chinase B by in situ click chemistry
approach.
• Solved crystal structure of transition state with alkene analog.
• Performed DFT calculations, but did not observe any enthaplic
barrier decrease.
• Confirmed in situ click chemistry principle that increase in reaction
rate is caused by entropic factors and greater effective
concentration.
• Solved crystal structures that demonstrate protein flexibility and
lack of in silico methods accuracy.