rapid synthesis and purification of sulfahydantion …...microwave assisted organic synthesis and...
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Rapid Synthesis and Purification of Sulfahydantion Library Using
Microwave Assisted Organic Synthesis and
Automated Flash Chromatography
Shahnaz Ghassemi, Ph.D.March 17, 2005
Discovery Chemistry Group1725 Discovery Drive
Charlottesville, VA 22911
2
Background
• Sulfahydantoin compounds are noted for their broad biological activity
• These conditions are not convenient for fast drug discovery
O NH
SO2N
R1 R
I
Pka comparable to carboxylic
acid ~ 4
• Most syntheses rely on long reaction time and tedious work-up process
3
This talk will overview the recent advances in technologies which has enabled the chemist to design efficient strategies to shorten reaction time and increase product purity
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Recent Advances for Rapid Synthesis and Purification
• Microwave Assisted Organic Synthesis (MAOS)
• Automated Flash purification
Shorten Compound production
time
ReproducibleresultsIncrease product
purity
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O
O
R1
R2
NH4OAC+ Microwave
180 °C, 5 min.
PhCH2Cl Microwave 180 °C, 5 min.
The First MAOS of alkaloid Lepidiline B
Wolkenberg, S.E.; Wisnoski, D.W.; Lindsley, C.W.; Zhao, Z.; Leister, W.; Wang, Y. Org. Lett. 2004, 6, 1453
43% over 2 steps
Total reaction time: 10 min N
+
N
R1
R2
N
NH
R1
R2H
O
Alkaloid lepidiline B
6
3 eq.
12-24 hr.
R.T
Conventional*
Temp
Solid-DCC
Time
Solid Supported Reagents in Controlled MAOS
Solid supported reagents are an important tool in solution phase chemistry– Eliminates reaction work-up– Real time monitoring
150 ºC
1 eq.
5 min.
Microwave
+OH
O
R R1
NR2
H
N
OR2
R1
RN N
DCM
Sillicycle.com/html/english/productsArgotech.com/products/lead/resins/index.htm
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MAOS + Solid Supported ReagentAMIDE COUPLING
Sauer,D., Kalvin, D., Phelan, K., Org. Lett. 2003, 5, 4721
A general and rapid method for the preparation of amides using bonded-carbodiimide + microwave heating
Microwave 5 min.
N
OHO
Ps- Carbodiimide
amine, HOBTNMP
N
NO O
N
NHO
N
NHO
N
NO
N
NO
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Sulfahydantion
General scheme for sulfahydantion
1. Reductive alkylation
2. Sulfamide synthesis
3. Cyclitive cleavage
Total time: 4 Days
O NH
SO2N
R1 R
I
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Sulfahydantion
O
NH2
OClH
4-MeOC6H4CHO
NaOAc, NaCNBH3
O
NH
O
OMe
O
N
O
OMeSO2NH2
O
N SO2
NH
MeO
Overnight reaction, followed by many
steps of extractions
Two days reaction, followed by extractions
and chromatography
One day reaction, followed by
neutralization and extractions
H2NSO2Cl ,Et3N
NaOMe,MeOH
Literature procedure
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Modifications in Sulfahydantion Synthesis Procedure
• Microwave irradiation used to shorten reaction time
• Solid supported CNBH used to eliminate liquid-liquid extraction and reduce reaction workup
• Automated flash chromatography used for fast isolation of product
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Instrumentation for MAOS
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Microwave-Assisted Reductive Amination
O NH2
O
OMe
HO
DIEA, MeOH+ Microwave
2 min.90 ºC
Microwave 3 min.80 ºC
-CNBH3
Imine
O
N
O
OMe
Total time for synthesis: 5 min
MAOS in one-pot two step reductive alkylation
Amine
O
NH
O
OMe
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Microwave-Assisted Reductive AminationRacemization study
• The extent of racemization in the two step one pot microwave-assisted reductive amination was studied by comparing 1H-NMR (500 MHz) of the LL and DL diastereomers
+
• No racemization was detected
NHBoc
O
NH
O
Et
LL
NHBoc
O
NH
O
Et
DL
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1H-NMR of DL diastereomer
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Microwave-Assisted Amine Synthesis
O
ONH
NH
OO
O
NHO
O
NH
O
CF3
O
NHO
O
O
NH
O
ClCl
NHO
O
OMe
NH
CF3
O
OBrNHO
ONH
Cl
O
O
Cl
Method A 84% 68%83%79%
75%88%88%89%85%Method A
Method A: 2 eq. 1 M NaCNBH4
Method B 79%74% 85% 63%
73%78%80%84%79%Method B
Method B: 2 eq. Si-CNBH4
Method C: 2 eq. PS-CNBH4
Method B 80%72% 73% 59%
65%81%77%80%80%Method B
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Microwave-Assisted Sulfamides Synthesis
H OH
O+ S
O
OCl NH2S
O
OCl NCO
Microwave
1 min. 90 ºC Helium
Total time for synthesis: 5 min
O
N
O
OMeSO2NH2
Et3N, DCM
Microwave 4 min. 80 ºC
O
NH
O
OMe
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Isolated yield of Sulfamides
O
O
NO S
Et
O
ONH2
65%
O
NO S
Et
O
ONH2
Cl Cl68%
NH
Boc
O
N
O
Et
SNH2
O
O
79%
NH
Boc
O
N
O
Et
SNH2
O
O
79%
NO
O
S OO
NH2
Br
67%
NO
O
S OO
NH2
ClCl
74%
O
ON
SNH2 O
O
70%
NO
O
S OO
NH2
CF3
76%
Product verified by 1H-NMR and MS
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Microwave-Assisted Cyclitive Cleavage
Total time for synthesis: 5 min
O
N SO2
NH
MeO
O
N
O
OMeSO2NH2
NaOMe / MeOH
Microwave
5 min / 100 ºC
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Sulfahydantion Compounds Isolated yields
NS
BrO ONH
O
67%
N
O
S NH
Cl
Cl
O O
74%
ON
S NHO
O
70%
NS
CF3O ONH
O
87%
O
N
O
SNH
OO
65%
N
ClCl
SOO
NH
O
68%
HNH
O
OO
N
SNH
O
O
79%
HNH
O
OO
N
SNH
O
O
79%
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Optimized Synthesis of Cyclic Sulfamide
Conventional method of synthesis
4 days
Microwave-assisted organic synthesis
1 hour
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Microwave-promoted synthesis
• Shorter reaction times– Minutes instead of hours– Rapid testing of creative ideas
• Growing interest in microwave synthesis– Many papers and reviews coming out in 2000- 2005
• Expanded reaction diversity – New avenues for chemistry– Possible to run more difficult reactions due to higher temperatures
• Reproducible results– Temperature and pressure controlled
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Optimized Purification Scheme
Advancement in rapid isolation of product using Normal phase and Reverse phase Automated
Flash chromatography
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Conventional Workup & PurificationOf Reductive Amination Product
1. Solvent is evaporated
2. The residue is suspended in 5% aq NaOH and extracted with EtOAc (x2)
3. Organic extract is dried over MgSO4
4. Concentrated under reduced pressure
5. Crude product is taken up in EtOAc and extracted with 5% HCl (x 2)
6. The combined aqueous extracts is neutralized with solid K2CO3
7. Cooled to <5 ºC in an ice bath, and treated with 50% aq NaOH
8. The aqueous layer was extracted with EtOAc (x 3)
9. The EtOAc extracts is combined, dried over MgSO4 and concentrated
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Reaction Mixture
Flash Workup & Purification Using Solid Bonded Reagent
1. Evaporate solvent in vial using N2 flow
3. Insert “Frit” on top of sample inside cartridge
4. Load cartridge into barrel & seal using “Dry-Loading Compression Head”
Dry-Loading Compression
Head
2. Transfer resulting solid onto cartridge
5. Run Automated Flash chromatography
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Flash Purification of Amine
O NH2
ODIEA, MeOH
+ Microwave 2 min.90 ºC
Microwave 3 min.80 ºC
-CNBH3
H
O
HNH
BOC
NH
BOC
O
NHO
TLC of reaction mixture
Flash isolation
TLC of collected product after
Flash
Total time for purification: 15 min.
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Flash Purification of Sulfamide
SO
OCl NH2
O
N
O
OMeSO2NH2
Et3N, DCM
Microwave 4min. 80 ºC
O
NH
O
OMe
Flash purification
Product
Total time for purification: 15 min
+
TLC of reaction mixture
Product
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Conventional Workup & PurificationOf Cyclitive Cleavage
1. Solvent evaporated under reduced pressure
2. Residue taken up in water and washed with ether
3. Aqueous layer acidified to pH <1 with conc HCl
4. Extraction with ethyl acetate (X 2)
5. Dry combined ethyl acetate extracts over MgSO4
6. Solvent concentrated under reduced pressure
O
N SO2NH
MeO
28 2
Flash Workup & Purification Solution Phase Organic Synthesis
2. Samplet inserted onto Flash+ cartridge
1. Reaction mixture transferred onto Samplet
3. Load cartridge into barrel and seal using “Dry-Loading Compression Head”
4. Run Automated Flash chromatography
C18 Samplet
C18 Cartridge
SP Automated Purification System
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C-18 Flash Purification of Cyclic Sulfamide
100% MeOH
10% MeOH
Total time for purification: 15 min
NS
CF3O ONH
ONaOMe / MeOH
Microwave
5 min. 100 ºC
NO
O
S OO
NH2
CF 3
Yield 87%
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1H-NMR of Cyclic Sulfamide
1H-NMR of cyclized product after Flash Purification
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Summary
• A general procedure for rapid preparation of sulfahydantions using Controlled microwave-heating and Automated Flash purification
– The products were formed in high yield and purity
– This procedure was demonstrated to be compatible with benzylic and aromatic aldehydes
• MAOS is easily integrated with Solid Bonded Reagents
– Less bonded reagent and shorter time required under microwave heating condition
• Simplifies workflow and enhances the rate of drug discovery
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Acknowledgements
• Dr. Pino Pilotti (Uppsala, SE)
• Dr. John Gupton (University of Richmond, VA)