microwave-assisted chemistry – from hts to...
TRANSCRIPT
Microwave-Assisted Chemistry– from HTS to CD
Jane Buus Laursen, PhDLead Generation
AstraZeneca R&D Mölndal
Outline
• Microwave infrastructure in Mölndal• Microwave-assisted chemistry in large
library synthesis• Microwave-assisted chemistry in lead
generation• Microwave-assisted chemistry in lead
optimisation
• 10 instruments, 9 of these have queue systems
– 4 Initiators (0.2-20mL)
– 1 Synthesizer (liquid handling, 0.2-20mL)
– 2 Creators (0.2-20mL)
– 3 Optimizers (0.2-20mL or 0.2-5mL)
• Open access
– Available locally to ~120 bench chemists
– Used regularly by >80% of these
Microwave equipment in Mölndal
• Knowledge Management– Electronic lab journal feeds
information to in-house reaction database
– Microwave-assisted reactions are searchable if “microwave reagent” is specified
• Usage– ~10% of all unique
reactions are done using microwave heating
Knowledge Management & Usage
Impact on cycle times
• Faster optimisation of reaction conditions– Quick failures
• Faster compound production– More time for evaluation and design
– Faster access to results leading to faster decision making
• Compound synthesis is no longer the bottle neck in lead generation thanks to microwave, parallel synthesis and purification techniques
CCE* library synthesis
• Acylated amino-phthalimides• 480-member library in a 20 x 24 matrix• Single compound scale: 200µmol• 3 synthetic steps (first step microwave-assisted)
O
O
N R1
NHX
R2
X = CO, SO2
*: Compound Collection Enhancement
J. Sundell & J.B. Laursen
Optimising reaction conditions
• Step 1: 1 eq R1-NH2, AcOH, e.g. an optionally substituted benzyl amine:
• Step 2: 0.1 eq Pd/C, H2 (1 atm), EtOAc/MeOH/AcOH (3:1:1), 3h, rt• Step 3: 2.5 eq R2XCl (X = CO, SO2), pyridine, 70°C, 16h or µW
O
O
O
N+ OO
O
O
N R1
NH2 O
O
N
NHX
R2
R1
O
O
N
N+ OO
R1
Step 1
X = CO, SO2
Step 3Step 2
~90% conversion7h70°C~95% conversion30min115°C
~30% conversion30h20°C
>95% conversion5minµW 170°C
ConversionTimeTemperature
J. Sundell & J.B. Laursen
Technical solution
• 480-member library in a 20 x 24 matrix
• Synthetic scale & equipment:
– Step 1: 5mmol (2×20mL microwave vials per reaction)
– Step 2: 5mmol (Radley carousel, 50mL flasks)
– Step 3: 200µmol (Bohdan MiniBlockTM, 4mL reaction tubes)
O
O
O
N+ OO
O
O
N R1
NH2 O
O
N
NHX
R2
R1
O
O
N
N+ OO
R1
Step 1
X = CO, SO2
Step 3Step 2
Microwave
×20 ×480×20
J. Sundell & J.B. Laursen
Lead generation library synthesis
• Imidazopyridines• 288-member library in a 6 x 48 matrix• Single compound scale: 200µmol
N
NNH2
R2
R1
E. Wellner
Synthetic route
N
NH2
R1 N+
NH2
O
Cl
Cl
R1 ClN
NO
HR1
N
NO
H
R2
R1N
NNH2
H
R2
R1
2 step one-potMicrowave-assisted
2 step one-potMicrowave-assisted
• 7 synthetic steps• 4 of these microwave-assisted
E. Wellner
Synthesis of imidazopyridinealdehydes
• Formation of the pyridinium salt limited by the nature of R1
• Cyclisation: Mixture of dichloride and acetal not separated
N
NH2
R1
O
Cl
ClCl
N+
NH2
O
Cl
Cl
R1 Cl
N
NCl
ClR1
N
NO
O
Et
Et
R1
N
NO
HR1
DME, RT
EtOHµW 120°C2000s
quant.
0.6 M HCl aqµW 120°C, 500s
90%
E. Wellner
Reductive amination
• Catalytic pivalic acid was used instead of HOAc to avoid acylation of the product.
• Hydrolytic conditions involve water/pivalic acid
N
NO
H
R2
R1
NH2
O O
N
NNH
H
O
O
R2
R1PS-NEt3CNBH3
N
NNH2
H
R2
R1EtOH/pivalic acid
µW 140°C, 1400s
not isolated
water/EtOH(37% pivalic acid)
µW 120°C, 540s
E. Wellner
N
NH2
R1N
+
NH2
O
Cl
Cl
R1 ClN
NO
HR1
N
NO
H
R2
R1
N
NO
O
Et
Et
R1
N
NNH2
H
R2
R1
Step 1 Step 2 Step 3
Step 4Step 5
Step 6Step 7
Microwave Microwave
Microwave
Practical solution
• 288-member library in a 6 x 48 matrix
• Synthetic scale & equipment:
– Step 1-4: 10mmol (conventional flasks, 20mL microwave vials)
– Step 5: 200µmol (Bohdan MiniBlockTM, 2mL)
– Step 6-7: 200µmol (1mL microwave vials, Synthesizer liquid handling)
×6
×288
×6 ×6
×288
E. Wellner
Notes on microwave-assisted MPS
+ Fast reaction times+ Walk-away time in library synthesis+ Can be combined with liquid handling robotics
– Capacity in queue system– Limitation in scale (< 10 mmol)– Post-synthetic handling
e.g. filtration, SPE, phase separators
– Capping / de-capping– Plate format (not 96-well)
Lead optimisation synthesis
N
N
N
OHO
O
• New pyrazinone shows to be less reactive• Calculation of activation energy to aid optimisation of
reaction conditions
U. Fahlander et al.Work presented in part at the 232nd ACS National Meeting, San Francisco, US, Sept. 10-14, 2006, MEDI 392.
Synthetic route
N
N
Cl
Cl
NH
OO
N
N
N
OO
Cl
N
N
N
OO
O
N
N
N
OHO
O
NH
N
N
OO
O
N O
O
+
EtOH / water 3:11.5 eq NEt3
µW 170°C, 20 min (80%)
reflux over night (72%)
2 eq. KOAcHOAc / water 7:1
reflux 5 h (92%)
µW 150°C, 10 min (87%)
4 eq. DMF
µW 150°C, 20min (90%)
reflux 3 h, thenr.t over night (68%)
5 eq. LiOH
reflux 90 min (66%)
• The obvious route:
• Alternative route:
N
N
O
Cl
NH
RNN
NO R
N
N
Cl
Cl
NH
RNN
NCl R
+
+µW 170°C, 20 min (80%)
reflux over night (72%)
µW 170°C, 20 min (0%)
U. Fahlander
Reaction rate
23.910 h
19.736 sec
21.10.1 h
22.51 h
∆G* (kcal/mol)t½
1.4 kcal/mol decrease in activation energy = 10 × reaction rate
10°C increased reaction temperature = 2 × reaction rate
A. Broo
K = ν exp(-∆G*/RT) t½= ln2/Kν = KbT/h ≈ 6.2*1012
Calculation of activation energy
• Can calculations explain the reactivity difference?
Activation energy (∆E‡) of SNAr reaction:
Ar
X
NH
N
Ar
23.03
17.77
21.64
23.3727.6122.8727.6822.0723.34Br
21.4726.7931.6926.0027.39Cl
Ar
N
N
O
X
N
N
OH
X
N
N
O
X
N
N
OH
X
N
N
O
Br
N
NH
O
Br
N
N
X
X
N
Cl
Cl
N
N
Cl
Cl
A. Broo
N
N
O
Cl
NH
R
N
N
N
O
R
+µW 170°C, 20 min (0%)
Calculations vs. results
NH
R
N
N
N
Cl
R
N
N
Cl
Cl
+µW 150°C, 20 min
62%
∆E‡ = 21.5 kcal/mol
∆E‡ = 27.4 kcal/mol
U. Fahlander & A. Broo
µW ~185°C (20 bar), 22h
69%
Results
N
N
Cl
ONH
OHO
N
N
N
OHO
O
+
µW 180°C (20 bar) 20 h (90%)
5 equiv. NEt3Ethanol / water 3:1
• The 4 step approach could be replaced by a microwave assisted 1-step synthesis:
U. Fahlander
”A good drug is hard to find-A perfect one takes longer”
ACS meeting, New Orleans, 1999
”A good drug is hard to find-A perfect one takes longer”
can be done!”AstraZeneca R&D Mölndal
Acknowledgements
• Colleagues at AstraZeneca Mölndal– Johan Sundell (CCE)
– Eric Wellner (Lead Generation)
– Ulf Fahlander (Lead Optimisation)
– Anders Broo (Computational Chemistry)
– Fritiof Pontén (Up-scaling lab)
– Niklas Falk (ChemInformatics)