The use and application of solid supported media in organic, medicinal and scale up chemistries
-leaping hurdles
Sunil Rana, Ph.D.Senior Scientist / Project ManagerDiscovery Chemistry Group
Overview
Solid supported reagents and scavengers
Background
Solid-supported reagents/scavengers
Phosphine chemistry: C-C bond formationReductive amination: C-N bond formationCatch and release: Amine purificationAlkylation: C-O / C-N bond formationOverview Coupling Chemistry: Amide bond formationOxidation Chemistry: FGI ‘O’Metal Scavenging The invisible obstacle
Brief History – Supports
1800-1901 Origins of Polymer and Silica Chemistry, 1838 first polymermodification (cellulose nitration), 1893 first lab styrene polymerization
1901-1935 Early Polymer Functionalization, early chlorophyll chromatography, Tsvet, first polymer supported catalyst (amylase / starch)
1945-1952 Industrial Polymer Utilization, ion exchange resins, water purification, silicas in cracking, butadiene synthesis, chromatography plate theory, Martin and Synge
1960-1980 ‘Modern’ SPPS, Merrifield, HPLC and Flash Chromatography, Still
1988-date Combinatorial Chemistry, revival of SPOC, solution phase organic synthesis, increasing use of functionalized silica (and other) materials, split and mix synthesis Furka, microwave methods, fixed bed systems for process and expedited drug discovery focus, and API metal scavenging
Advantages of Solid Supports
Reduction of Bench TimeEasy and fast to dispense and useWork flow enhancements / costEasy dispose / potentially recyclable
Health and Safety
Removal of toxic by-products Stable, Storage, much simpler Safety / Health (TSE) statements
ChemistryHeterogeneous propertiesDefined loadingsEnhanced chemistry
precedence Med Chem Large Scale
X
XXXXXXXXX
XXX
XXXXXX
XX
XX
XXXX
XX
XX
XX
XX
XX
XXX
X
Resins and Silicas
Mostly surface orientated chemistryRobust irregular shaped particlesSi-OH terminal groupsInsoluble polymerSi-O-Si matrix
Insoluble, cross-linkedPolystyrene Spherical 50um – 1000um diameterFormal pore structure
Insoluble, cross-linkedPolystyrene Spherical 50um – 1000um diameterNo Formal pore structure
Process / Properties
ScavReagent
Core Product
Reagent
ReagentScavProduct
Filter to Purify
PS-, MP- and Si Supports – A Comparison
Material Size Volume Loading Swelling Protic (polar)
Aprotic Friability
Silica 40-60 2mL/g 0.5-2 mmol/g No√ √
Yes
PS gel 75-150 2-8mL/g 1-3.5 mmol/g Yes X √ Yes / partial
MP resin 150-1000 2-4mL/g 1-4.5 mmol/g Partial / no √ √ No / partial
Scavenging Benzylamine: 3.5 Equiv. PS- or MP-Isocyanate/ RT
2
20
THF MP-Isocyanate
THF PS-Isocyanate
MeOH MP-Isocyanate
MeOH PS-Isocyanate
0
20
40
60
80
100
1
20
MeCN MP-Isocyanate
MeCN PS-Isocyanate
MTBE MP-Isocyanate
MTBE PS-Isocyanate
0
20
40
60
80
100
0
1
2
3
4
5
Volu
me
Dry DCM THF Methanol Water
500mg MP-TMT per Solvent
Current Obsolete Gel PS
R1 R2
ON
NH
R2
R11) NH2NH2
70 °C, 3h2) PS-CHO
N-Substituted Pyrazoline Libraries
Chalcones used as templates for pyrazoline library
Bauer, U. et al. Tetrahedron Lett. 2000, 41, 2713-2717
Synthesis1, R3COCl, PS-DIEA; 2, R3NCO; 3, R3SO2Cl, PS-DIEA; 4, R3OCOCl, PS-DIEA
PurificationPS-Trisamine, PS-Isocyanate cocktail
NN
R2
R1
NN
R2
R1
NNS
R2
R1
NN
R2
R1
R3
HN
O
O
O R3
O R3
OO
R3
1
2
3
4
N-Substituted Pyrazoline Libraries
• 80 chalcones converted to 1500 derivatives• Purities = 75 – 98%• Representative structures
NN N
NN
NS
NHO O
O
OO
N
Ph
S S
N
ClCl
S
NN
NN
O NMe2O
OMe
Cl82% Yield> 95% Purity
84 %Yield91 %Purity
87 %Yield89 %Purity
75 %Yield88 %Purity
Bauer, U. et al. Tetrahedron Lett. 2000, 41, 2713-2717
PS-Triphenylphosphine
Wittig Chemistry
Chlorination
Mitsunobu Chemistry
HalideScavenging
ROH
R Cl
R OH
R Cl
O
O
3 hrs, reflux,100% yield100% purity
R OH
+ DBADi.
ii. R' OH
R'O
R
R / R' = aryl / alkyl
75-95% yield, 100% purity, RT conditions
100%removalfrom solution,RT, 6-16 hours
R X
PPh2
R
X
P
Alkyl Halides
PPh2R
XNaHMDSR2COR3
R X
Alkene Synthesis
R2 R3
R1
Ether Synthesis
work-up
microwave
R OH
OR' NHNH2
O
+
N N
OR'
R
1,3,4-oxadiazoles
I
O2Nmicrowaveheating
Pd(OAc)2 CN
O2N
N Zn N
Aryl cyanides
PS-Triphenylphosphine : Chlorination
2 Wang, Y.; Miller, R.L.; Sauer, D. R. Djuric, S. W.; Org. Lett. 2005, 7(5), 925-928
Acid Chloride formed in-situ, quantitative yields
React with aldoximes generating the oxadiazole, one pot
77-98 %
OH
O
BnO
+ NH2
NOH
BnON
NO(i) PS-PPh3 (3 equiv); CCl3CN (1.5 equiv),100°C, 5 min
(ii) DIEA (2 equiv); Aldoxime; THF, 150°C, 15 min
1 From Rana, S., Gooding, O., Labadie, J. 2003 Unpublished optimized procedures
R-OH or R-CO2HPS-PPh3 (2 equiv)
CCl4, ref lux100% (100%)
98% (95%) 73% (95%)
1
2
PS-PPh3-Pd : Suzuki Coupling
Reactions performed under air, no inert conditions requiredProducts isolated in high purity and yieldLow palladium level in products (< 60 ppm)
BrR1 R2
B(OH)2
R1
R2
+i. 0.5 mol% PS-PPh3-Pd
1.0 equiv 1.2 equivii. K2CO3,DME:EtOH:H2O (2:2:1)75 oC, 16 h
P PdLn
Stable to air, light and moistureStable at room temperature Supported catalyst simplifies product isolation
PS-PPh3-Pd / Si-Carbonate: Enhanced Workflow
N+(CO 3)-2
0.5
Si
N
O
O2N
Ghassemi, S. ACS, Atlanta, GA, March 2006
~ 5 mins
N
O
Br+ O2N B
OH
OH
N
O
O2N
µW 130 °C, 10 minEtOH / DME (1:1)
Cs2CO3, PS-(PPh3)nPdO2N B
OH
OH
+
MP-BH(OAc)3 [Bound Triacetoxyborohydride]Tolerates acid-sensitive groups: ketals, acetals. Secondary amines isolated as acetate. Tertiary amines as free base
NEt3 (OAc)3BH
NEt3 BH4
Reductive Amination – Supported Approaches
NEt3 (CN)BH3
MP-BH3CN [Bound Cyanoborohydride]Requires acetic acid, Similar reactivity and scope, Masked toxicity (CN- stays resin bound)
MP-BH4 /Ti(iOPr)4 [Bound borohydride]Suppress over-alkylation (reactive C=O)Enables use of: sterically hindered carbonyls e.g. adamantyl ketones, enolizable ketones e.g. acetophenone.
Powerful reaction for amine synthesis. Commonly facile reactions with predictable outcomes, thus amenable to parallelization, but work up can limit
+
i. 1.4 equiv. NaBH(OAc)3 (1 equiv. HOAc) RT, 1-16 h
R1NH2
R2 R3
O
R1NH
R3R2
1-1.2 equiv.
ii. 1M NaOHiii. Etheral extractioniv. Wash, dry v. Column purification
Typical solution-phase protocol
Expedited bound reagent protocol
+R1
NH2R2 R3
O
R1NH
R3R2
1-1.2 equiv.
i. 2.5 equiv MP-BH(OAc)3 RT, 1 - 16 h, THF
ii. 1 equiv PS-CHO, 6 hiii. Filter, wash, concentrate
Synthesis of Secondary Amines
Bhattacharyya, S. ; Rana, S.; Gooding, O. W.; Labadie, J. Tetrahedron Lett. 2003, 44, 4957-4960
Water of imine formation hydrolyzes ~ 1 equiv BH(OAc)3
Facilitates scavenging, additional HOAc not required
MP-BH(OAc)3 : Synthesis of Secondary Amines
O
O
O
93 (100) 77(84)16 77 (100)
93 (98) 90(96)3 91(100)
%yield (%purity)%overalkylation
ON NH2
N
O
76(27)
69(98)
NH2
NH2 100 (100) 94 (88)12 54(100) 39(91)
O
O
Labadie, J.; Rana, S.; Lindberg, T.; Gooding, O. W.; Bhattacharyya, S. 222nd National Meeting American Chemical Society, Chicago, IL; ORGN 517.
+i. THF
ii. 2.0 equiv. MP-BH(OAc)3R1
HN
R2 R3 R4
O
R1N
R2
R4R3
iii.PS-NCO (1.0equiv.), 6 h1.1 equiv. 1.0 equiv.
MP-BH(OAc)3 : Synthesis of Tertiary Amines
N NH
O NH
NH
O O
97(100) 92(99) 88(100) 85(100)
63(100) 90(99) 69(100) 64(100)
67(100) 77(99) 82(100) 76(100)
%yield (%purity)
O
OO
O •Ketal tolerated
•Resin scavenger PS-NCO (1 equiv, 5- fold xs wrt amine)
•Product isolated as free amine
•Negligible B leaching
•PS-Isocyanate removes excess secondary amine
Reductive AminationSupported Purification Strategies
R3
R2
NArR1
R4
R5
O
Excess
R3
R2
NArR1
R3
R2
NArR1
(Excess)
R-NH2
Scenario 1Scenario 1 Scenario 2Scenario 2 Scenario 3Scenario 3
NH3/MeOH
Release
SO3H
SO3 R-NH3
Wash
R4
R5
O
Excess
R3
R2
NArR1
Catch O
N R
R1 = H R1 ≠ H
R3
R2
NArR1
(Excess)
NH
ArR1+
NCOWash
HNO
HN Ar
R3
R2
NArR1
Wash
1. Condition with DCM, DMF or methanol
2. Apply sample 3. Wash withorganic solvent
4. Release product with4 M ammonia/methanol
AmineCaught
Non-basic impurities washed
away
AmineReleased
Fixed Bed Approaches towards Amine purification
SO O
OH
Supported sulfonic acid equivalent, pKa(bound)~2-3Scavenge amines / basic compounds by ion pair formation
‘Elution Step’
MP-BH(OAc)3 : HCl salts and DMF - Summary
Amines as HCl salts, or insoluble in common solvents
Catch and Release protocol
Purify product + Remove DMF in one procedure
R-NH2. HClR1 R2
O i. 3.5 eq MP-BH(OAc)3
ii. (DMF solvent)+
iii. Catch and Release
RHN R1
R2(1.2eq)
HCl.NH-Tyr-(OBnz)-CO2Me cHexanone 60%(93%)
Yield% (purity %)
HCl.NH-Tyr-(OBnz)-CO2Me cHexane-CHO 74%(98%)
HCl.NH-Val-CO2Me cHexanone 59% (98%)
HCl.NH-Val-CO2Me cHexane-CHO 93% (99%)
Simultaneous BOC-deprotection & Amine Purification : Unsymmetrical Sulfamides
SNCO
OCl O
OH
DCM 0°C
SHN
OCl O
O
O
Amine / Aniline
80°C, 5 min, µW
SHN
ON O
O
O
R2
R
SHN
ON O
O
O
R2
R
THF, 80°C, 1-4 min
R3-OH, PPh3, DEAD SN
ON O
O
O
R2
R
R3
SO3H
µW, 100°C, 5 minMeCN / DCM
SO3SH2N ON
O
R2 RR3NH3 / MeOH
SHN ON
O
R2 R
R3
yield (72-89)% purity (98-99)%
Ghassemi, S. et al. Molecular Diversity, 2005, 9, 295-299
Si bound sulfonic acid, (‘SCX2 SCX 3’ Materials)– spontaneously remove BOC- protected amine group – purify the free amines via “Catch & Release” mechanism
O NH
OR
SO3H
DeprotectionSO3 H3N R
NH3 / MeOH
Release(Purification)
R-NH2
NN
N
•PS-bicyclic guanidine (1,5,7- triazabicyclo[4.4.0]dec-5-ene )
• Stronger base than PS-DIEA, PS-NMM
• Deprotonation of moderately acidic hydrogens, pKa 13-15
• Applications Include:
• Alkylation of phenols, amines, active methylenes
• Esterification of carboxylic acids
Morrissey, M.; Mohan, R.; Xu, W. Tetrahedron Lett 1997, 38,7337
Organ, M.G.; Dixon, C.E. Biotechnol. Bioeng. (Comb. Chem) 2000, 71, 71-77
PS-TBD
ArOHTBD: TBD:H+
ArO-+R-Br TBD:H+
Br- + ArO-R
"Catch" "Release"
0
204060
80100
% Resin Bound Phenolate
1.0 eq in THF 1.0 eq in MeCN
4-Phenylphenol + 1 eq. PS-TBD
PS-TBD : Catch and Release
PS-TBD: Williamson Ether Synthesis
Ar-OH (1.1 equiv.)
i. PS-TBD (3.0 equiv.)
ii. RBr (1.0 equiv.)ArOR
MeO O
O
BrBr
OBr
O7
OBr
MeCN 55C, 16 hrs THF 25C, 16 hrs
Purity % Yield % Purity % Yield %
100 91 100 90
100 90 17 45
100 95 89 38
100 90 100 77
100 85 100 91
Product
Original Conditions: See Williamson, A. Justus Leibigs Ann. Chem. 1851, 77, 37-49, 81, 373.
NHN NO2NN NO2
OO
BrO
O+
130°C, 10 min
-NCO
100°C, 5 minSolvent Solvent
-TBD
Lundin, R. www.biotagepathfinder.com
Introductory Amide Synthesis
• PS-Carbodiimide - Coupling Agent
– One-step amide synthesis– Scavenging may be required– Rearrangement to acylisourea can be
problematic ---Can be solved by addition of HOBt
• PS-HOBt - Active Esters
– Two-step process– Amine = limiting reagent in acylation,
affords high purity amides– Storable reactive intermediate
NN
O2S
NH
NOH
O N=C=N
PS-Carbodiimide:Microwave Assisted Synthesis
N
OHO
+ R1R2NHN
NR1R2O
98% Yield98% purity< 15 min
1) PS-Carbodiimide, HOBt, DMA uW, 100 oC, 5min
2) Si-Carbonate
O NH
R1R2NH =
BnNH2 PhNH
Me
N
NHMe
High yield, high purity using filtration, Si-CO3 cartridge based purification
•D. Sauer et.al. Organic Letters 2003, 24, 4721-4724
PS-Carbodiimide/ Si-CO3 Rapid Acylation & Purification
Ghassemi, S. ACS, Atlanta, GA, March 2006
I
NH
O
99% yield, 98 % Purity
N+(CO 3)-2
0.5
Si
Synthesis + Purification ~ 10 mins
I
COOH
NH3TsO+
PS-Carbodiimide
HOBt, DIEAµW, 100°C, 5 min
I
HN
O
NN
N
OH
+
I
COOH+
Unreacted acid
AU
0.00
0.10
0.20
0.30
0.40
0.50
Minutes2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00
2.38
7
8.05
3HOBt+
AcidProduct
Reaction Mixture
AU
0.00
0.20
0.40
0.60
0.80
1.00
1.20
Minutes2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00
2.50
1
7.96
7
Product
PS-Carbodiimide for Benzimidazole Synthesis
NH2
NHR2R1 NH
NHR2R1
O
R3
1. PS-Carbodiimide, HOAt,R3COOH
2. PS-Trisamine N
NR3R1
R2
HOAc
90 oC/16h
Applied to selective acylation of diamineImidates, thioimidates, acyl halides failedHOAt performed better than HOBt70% conversion with HOBt
Applied to library of 96 1,2-diarylbenzimidazoles>95% purity for 85% of products
Yun, Y.K.; Porco, J.A.; Labadie, J. SynLett. 2002, 5, 739-742.
Amides From Active Ester Resins
PS-HOBt: Pop, I.E. et al., J. Org. Chem. 1997, 62, 2594
NH
SOO
NN
NOH
XO R
O
X
R1HN R
O
PS-HOBt
Active Ester Resin
Acid Coupling
Parallel Acylation
Amides
R1NH2 R2NH2 R3NH2
R2HN R
O
R3HN R
O
.....
PS-DIEA, Si-Carbonate, Si-TsOHRapid Amidation and workup
59% yield97 % Purity
NiPr
iPrPS
N
O
Br
NH
COOHBrN
OBr
NHNH
+PS-DIEA, HATU
µW, 110-150 oC 6-12 min
+
Ghassemi, S. ACS, Atlanta, GA, March 2006
N
OBr
SO O
O-
Si
N+ (CO3)-20.5
Si
Catch & Release
MP-TsO-TEMPO: Supported Oxidizing Agent
• MP-TsO-TEMPO is a bound oxoammonium sulfonate• Oxidation of benzylic, allylic, acetylenic and cyclic secondary
alcohols• Highly controlled reaction. No over-oxidation to acid.• Stable• Resin is a mixture of active oxoammonium and reduced
hydroxylammonium species.
NSO3 H
OH
O3SN O
MP-TsO-TEMPO(As provided)
MP-TsO-TEMPOOxidation of Alcohols
OHR
SO3 N+
OO
R
+- Solvent
Temp / Time
Alcohol Method Solvent Temp Time Yield
Non-µW CH3CN rt 16 h 95 %
µW DCM 100 oC 10 min 100 %
Non-µW CH3CN rt 16 h 99 %
µW DCM 60 oC 2 h 100 %
Non-µW CH3CN rt 16 h 70 %
µW DCM 60 oC 5 min 93%
Non-µW DCM rt 16 h 70 %
µW DCM 60 oC 1.5 min 100 %
Non-µW DCM rt 16 h 100 %
µW DCM 60 oC 2.5 min 100 %
O
OH
OH
Br
OH
OH
OH
OH
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Pharmaceutical Metal Limits
MetalConcentration (ppm)
Oral Parenteral
Pt, Pd, Ir, Rh, Ru, Os 5 0.5
Mo, V, Ni, Cr 10 1
Cu, Mn 15 1.5
Zn, Fe 20 2
• Current acceptable limits:
• Permitted limits of metals in API, fine and speciality chemicals will continue to decline
• New technology required to meet this challenge
European Agency for the Evaluation of Medicinal Products
Palladium Scavenging: Resin Based Advances
S N
NN
SH
SH
Br+
B(OH)2
OMe
PdCl2(PPh3)2
Aq. Na2CO3, Toluene80 °C, 24 h, inert atmosphere
work-up
OMe
Product + PdLn
5-10 equiv,rt, stir 4-16 h
HO
HO
OMeHO
33400 PPM Pd (ICP) <190 PPM Pd (ICP)
Scavenges ligated palladium [0],[II]Aqueous and non-aqueousCompound Polishing
0
75.5 87 98.6
050
100
0 1 2 18
% scav 2 equiv resin with time
Si-TMT : Synthesis of Benzothiazoles
N
SCl +
Pd(PPh3)4 , 0.4mol%
Na2CO3, 2.4eqDioxane / H2O
N
S
Batch (5eq)
Flow (500mg/3mL)
Flow (100mg/3mL)
+ Pd [n]
'Chemical' Purification [PE-AX/SCX2][M+H]+ = 218
S
B(OH)2
S
S N
NN
SH
SHSi
S.Rana, Unpublished Results, Biotage 2007,
Method as per: Heo,Y.; Song, Y.S.; Kim, B.T.; Heo, J. Tetrahedron Lett. 47 (2006), 3091-3094
Si-Thiol Si-Thiol Si-TMT
Batch (5eq) 91% 82% >99% Fixed Bed 100mg 45% 45% 95%Fixed Bed 500mg 86% 91% >99%
538.1
4.2 17.0 14.5
0
100
200
300
400
500
600
PPM
in s
olut
ion
Si-Thiol Si-TMT MP-TMT Resin-TMT
S N
NN
SH
SHS N
NN
SH
SHSi
69eq 16eq 35eq 35eq
SHSi
Initial Concentration 1000ppm Pd
Fixed bed: 500mg / 3mL std fritted polyprop cartridge
Gravity flow, one pass
Bound-TMT / Dichlorobis(DPP)ferrocene Palladium
Dichlorobis(DPP)ferrocene Palladium (THF/DMF)
Efficiency a factor of min: particle size, ligand, packing
Metal Scavenging – an re-emerging technolgy
Initial Work in optimizing a colourimetric metal screen. Catalyst Pd(Cl)2(PPh3)2 in DMF / THF (1:1)
0
0.5
1
1.5
5.0 10.0 20.0 30.0 40.0 50.0
Mass bound media (mg) in scavenging assay
Abs
orba
nce
units
MP-TMT Si-Tris PS-Trisamine
MP-Trisamine PS-Deam Si-Triamine
N+
OH
H Cl-
Activation
ReactionN+
OH
H Cl-
NO OSO
O
NOSO
OO
Cl
OHR2
R1O
R2
R1exhausted form
of resinsupplied form(50% active)
N
O
O
Cl NH
O
O
Cl2
HCl
recyclable
can undergodisproportionationthus rearangement
PS-TEMPO – pipeline
PS-sulphonic ester linked 2,2,6,6-tetramethylpiperidine-1-oxyl species
Thank you for your attention
