Mechanistic Studies of Thiol Oxidation by F NMR Kaitlyn_UROP Poster.pdfContact [email protected]...
1
Reaction Kinetics by 1 H NMR • The process of thiol oxidation is much more complex than a ‘textbook reaction’. This is presumably due to the high reactivity of sulfenic and sulfinic acids towards oxidation, rendering it nearly impossible to isolate(2). • The isolation and characterization of these intermediates has yet to be determined. • Previous research in our laboratory enabled the synthesis of a persistent sulfenic acid; 9-tripticene sulfenic acid(3). • The high steric hindrance of the triptycene backbone plays an important role as a protecting group in the stabilization of the sulfenic acid. This structure will enable the complete characterization and kinetic analysis of thiol oxidation reactions(1). • Monitoring the reaction kinetics by 19 F NMR is a more efficient way to collect kinetic data while minimizing product handling and cost. • d 3 -MeOH = $150/5g 1. McGrath, A. J.; Garrett, G. E.; Valgimigli, L.; Pratt, D. A. J. Am. Chem. Soc. 2010, 132, 16759. 2. Amorati ,R.; Lynettt, P.T.; Valgimigli, L.; Pratt, D.A. Chem.Eur.J.. 2012,18,6370-6379 3. McGrath, A.J. Synthesis, Redox Chemistry and Antioxidant Activity of Sulfenic Acids. Unpublished master thesis , Queens University, Kingston, Ontario. Contact [email protected] Mechanistic Studies of Thiol Oxidation by 19 F NMR Kaitlyn Margison, Jean-Philippe R. Chauvin & Derek A. Pratt* Department of Chemistry, University of Ottawa, Ottawa, ON, Canada Introduction Kinetic Data Future Work • Above are the authentic standards to be synthesized and analyzed through 19 F NMR. • The intermediate products of thiol oxidations have been found to play a role in a increasing number of chemical and biological processes such as signal transduction, protein folding and enzymatic processes(1). • For example, glutathione, a tripeptide containing a nucleophilic thiol, is present in high concentration (up to ~5mM) in cells and offers a line of defense against oxidative stress. Synthesis of Triptycene Thiol Oxidation Products References Acknowledgements N H O NH2 HOOC HS H N COOH O t = 0 min 0 20 40 60 80 100 0 500 1000 1500 2000 2500 3000 % [Trp] 0 t (s) [TrpSH]0 = 5mM TrpSH TrpSOH TrpSO2H 0 20 40 60 80 100 0 500 1000 1500 2000 2500 3000 3500 4000 % [Trp] 0 t (s) [TrpSOH]0 = 5mM TrpSOH TrpSO2H TrpSO3H 0 20 40 60 80 100 120 0 500 1000 1500 2000 2500 3000 3500 4000 % [Trp] 0 t (s) [TrpSO2H]0 = 5mM TrpSO2H TrpSO3H SH SOH SO2H SO3H Glutathione Reactivity with different oxidants: oH 2 O 2 oAlkyl-OOH oHOCl Method optimization to get reproducible data oDetermine kinetics oKinetics vs pH Synthesis of fluorinated analogues oKinetics in a variety of solvents . Synthesis of Fluoro-Triptycene Sulfinic Acid t=240 min SH HOS HO2S HO3S + + O HO 50-100mM d3-AcN:D2O(9:1) DMF, Amine Buffer f-trp thiol f-trp-sulfenic acid f-trp sulfinic acid f-trp sulfonic acid SH HOS HO2S HO3S [O] [O] [O] F F F F Figure 2. The oxidation of thiols towards sulfenic and sulfinic acids occurs fairly rapidly. There exists a decline in reactivity as the products become more oxidized. As observed, thiol is more reactive than sulfenic acid and sulfenic acid is more reactive than sulfinic acid. UROP Undergraduate Research Opportunity Program Route 1 Route 2 Route 3 HS OH O NH2 Cysteine R S H H R S R R 2H+ + 2e- + + disulfide bond oxidation fluoro-t-butylthiotriptycene •Synthesis of the targeted fluorinated t-butylthiotriptycene will enable the production of the thiol, sulfenic acid and sulfonic acid standards. S F NaH, THF HS Br Br F F 1) BuLi, THF 2)NFSI F S Figure 1. At t=0 largely only thiol is observed, but as the oxidation continues to t=240min, four well separated peaks are observed. Each peak is labeled according to the observed thiol oxidation product second NMR. This obvious separation challenges the ‘textbook reaction’ stigma and prompts further understanding of the oxidation. A similar, yet more informative analysis is expected to be achieved through 19 F NMR. SH HOS HO2S HO3S + + O HO 50-100mM d3-AcN:D2O(9:1) DMF, Amine Buffer Br NaI, CuI, DMEDA Dioxane, reflux t-BuSh, CuI, NaOt-Bu,1,10-phen S N2 + CO2 - DCE, 60°C S mCPBA CH2Cl2 0°C to rt 59% SOH I Toluene, microwave TfOH, TFA Toluene, 80°C 84% SH SO3H H2O2 MeOH,rt 96% Br Br F F 1) BuLi, THF 2)NFSI ,CuI K t OBu, 1,10 phen, toluene SH S S major product NaH, THF F S SH 68% N S S F HO2S N OH O NH2 CCl3 OH O Isoamyl Nitrile THF, 0°C OH O N2 + F Br F Br F N S RuCl 3 1) BuLi 2) Benzene/MTBE, -20°C 71% NaIO4 H2O: EtOAc 65°C EtSH, NaH THF, 0°C-70°C 78% F N S O O DCE, 60°C Br F F Br F I F S 1)BuLi,-78°C, THF 2)NFSI CuI, NaI DMEDA, Dioxane,120°C HS CuI, tBuOK Toluene 120 hr BuLi, -78°C THF S S F S NBS
Transcript of Mechanistic Studies of Thiol Oxidation by F NMR Kaitlyn_UROP Poster.pdfContact [email protected]...
Reaction Kinetics by 1H NMR
• The process of thiol oxidation is much more complex than a ‘textbook reaction’.
This is presumably due to the high reactivity of sulfenic and sulfinic acids towards
oxidation, rendering it nearly impossible to isolate(2).
• The isolation and characterization of these intermediates has yet to be determined.
• Previous research in our laboratory enabled the synthesis of a persistent sulfenic
acid; 9-tripticene sulfenic acid(3).
• The high steric hindrance of the triptycene backbone plays an important role as a
protecting group in the stabilization of the sulfenic acid. This structure will enable
the complete characterization and kinetic analysis of thiol oxidation reactions(1).
• Monitoring the reaction kinetics by 19F NMR is a more efficient way to collect kinetic
data while minimizing product handling and cost.
• d3-MeOH = $150/5g
1. McGrath, A. J.; Garrett, G. E.; Valgimigli, L.; Pratt, D. A. J. Am. Chem. Soc. 2010,
132, 16759.
2. Amorati ,R.; Lynettt, P.T.; Valgimigli, L.; Pratt, D.A. Chem.Eur.J.. 2012,18,6370-6379
3. McGrath, A.J. Synthesis, Redox Chemistry and Antioxidant Activity of Sulfenic Acids.
Unpublished master thesis , Queens University, Kingston, Ontario.
Contact [email protected]
Mechanistic Studies of Thiol Oxidation by 19F NMR Kaitlyn Margison, Jean-Philippe R. Chauvin & Derek A. Pratt*
Department of Chemistry, University of Ottawa, Ottawa, ON, Canada
Introduction
Kinetic Data
Future Work
• Above are the authentic standards to be synthesized and analyzed through 19F NMR.
• The intermediate products of thiol oxidations have been found to play a role in a
increasing number of chemical and biological processes such as signal
transduction, protein folding and enzymatic processes(1).
• For example, glutathione, a tripeptide containing a nucleophilic thiol, is present in
high concentration (up to ~5mM) in cells and offers a line of defense against
oxidative stress.
Synthesis of Triptycene Thiol Oxidation Products
References Acknowledgements
NH
O
NH2
HOOC
HSHN COOH
O
t = 0 min
0
20
40
60
80
100
0 500 1000 1500 2000 2500 3000
% [T
rp] 0
t (s)
[TrpSH]0 = 5mM TrpSH
TrpSOH
TrpSO2H
0
20
40
60
80
100
0 500 1000 1500 2000 2500 3000 3500 4000
% [T
rp] 0
t (s)
[TrpSOH]0 = 5mM
TrpSOH
TrpSO2H
TrpSO3H
0
20
40
60
80
100
120
0 500 1000 1500 2000 2500 3000 3500 4000
% [Trp] 0
t (s)
[TrpSO2H]0 = 5mM
TrpSO2H
TrpSO3H
SH
SOH SO2H
SO3H
Glutathione
Reactivity with different oxidants: o H2O2 o Alkyl-OOH o HOCl
Method optimization to get reproducible data o Determine kinetics o Kinetics vs pH
Synthesis of fluorinated analogues o Kinetics in a variety of solvents
.
Synthesis of Fluoro-Triptycene Sulfinic Acid
t=240 min
SH HOS HO2S HO3S
+ +
OHO50-100mM
d3-AcN:D2O(9:1)DMF, Amine Buffer
f-trp thiol f-trp-sulfenic acid f-trp sulfinic acid f-trp sulfonic acid SH HOS HO2S HO3S
[O] [O] [O]F F F F
Figure 2. The oxidation of thiols towards sulfenic and sulfinic acids occurs fairly rapidly. There exists a decline in reactivity as the products become more oxidized. As observed, thiol is more reactive than sulfenic acid and sulfenic acid is more reactive than sulfinic acid.
UROP Undergraduate Research Opportunity Program
Route 1
Route 2
Route 3
HS OH
O
NH2
Cysteine
R S H H S R
SR S R 2H+ + 2e-
+
+
disulfide bond
oxidation
fluoro-t-butylthiotriptycene
• Synthesis of the targeted fluorinated t-butylthiotriptycene will enable the production of the thiol, sulfenic acid and sulfonic acid standards.
S
F
NaH, THF
HSBr
Br
F
F
1) BuLi, THF
2)NFSI
F
S
Figure 1. At t=0 largely only thiol is observed, but as the oxidation continues to t=240min, four well separated peaks are observed. Each peak is labeled according to the observed thiol oxidation product second NMR. This obvious separation challenges the ‘textbook reaction’ stigma and prompts further understanding of the oxidation. A similar, yet more informative analysis is expected to be achieved through 19F NMR.
SH HOS HO2S HO3S
+ +
OHO50-100mM
d3-AcN:D2O(9:1)DMF, Amine Buffer
Br NaI, CuI, DMEDADioxane, reflux
t-BuSh, CuI,NaOt-Bu,1,10-phen S
N2+
CO2-
DCE, 60°CS
mCPBA
CH2Cl20°C to rt
59%
SOH
I
Toluene, microwave
TfOH, TFAToluene, 80°C
84%
SH
SO3HH2O2
MeOH,rt96%
Br
Br
F
F
1) BuLi, THF
2)NFSI,CuI
KtOBu, 1,10 phen, toluene
SH
S
S
major product
NaH, THF
F
S
SH
68%
N S S
F
HO2S
N
OH
O
NH2
CCl3 OH
O
Isoamyl Nitrile
THF, 0°COH
O
N2+
F
Br F
Br
F
NS
RuCl31) BuLi
2)
Benzene/MTBE, -20°C71%
NaIO4
H2O: EtOAc65°C
EtSH, NaH
THF, 0°C-70°C78%
F
NS OO
DCE, 60°C
Br FF
Br
F
I
F
S
1)BuLi,-78°C, THF
2)NFSI
CuI, NaI
DMEDA,Dioxane,120°C
HS
CuI, tBuOKToluene120 hr
BuLi, -78°C THF
S S
F
S
NBS
