Simulated Moving Bed
Chromatography and Chiral
Compounds
Geoffrey B Cox
CHIRAL TECHNOLOGIES,
INC.
ISPE Toronto September 29 2005
Outline
z
z
z
z
z
z
z
Why enantioselective chromatography?
Alternatives
What is SMB?
How does it work?
How to develop a SMB process?
How to optimise SMB?
Economics
Chirality
Why does chirality matter?
z
z
Living systems are chiral
The body’s receptors for
–
–
–
–
z
Drugs
Flavours
Perfumes
Etc
are also chiral
The enantiomers of a chiral molecule
will interact differently with these
receptors
Enantiomers
z
z
z
z
z
z
(R)-(+)-limonene - fresh citrus, orange-like
(S)-(-)-limonene - harsh, turpentine-like, lemon note
(1R,2S)-(+)-Z-Methyl epijasmonate - Strong odor;
floral, true jasmin-like
(1S,2R)-(-)-Z-Methyl epijasmonate - odorless
Thalidomide
Omeprezole – S enantiomer active, R enantiomer
inactive
The Chiral Challenge
z
Discovery by combinatorial approach often
ignores chirality
You need small amounts of each
enantiomer, now!
You’ll need gram quantities next month
You’ll need kilograms next year
z
You will need tons upon launch
z
z
z
Means to a chiral end
z
Crystallisation
–
–
z
Kinetic resolution
–
z
z
z
Conglomerates – direct crystallisation (Aldomet)
Diastereoisomeric salts (Naproxen)
Biotransformations
Stereoselective Synthesis (hydrogenation etc)
Synthesis from the Chiral Pool
Chromatography (UCB, Lundbeck, Pfizer –
Sertraline*)
* Presentation Chirality 2004, New York
Preparative Chromatography
z
z
z
Chromatography is the quickest and surest
route to initial supplies of purified
enantiomers
Chromatography is often the quickest and
surest route to intermediate supplies of
desired enantiomer
Chromatography may be the most
economical means to produce commercial
supplies of drug
Reasons not to use chromatography
z
“You can’t do chromatography at scale”
–Currently 7 SMB installations 10-75 MT/year
z
“It’s expensive”
–estimates average < $100/kg API
–this adds 10c to a 100 mg pill that sells for…..
–consider opportunity costs –what could your talented chemists be
doing instead?
z
“Real chemists don’t need chromatography”
– ???
–“The power of these high pressure liquid chromatographic methods hardly can be
imagined by the chemist who has not had experience with them; they represent relatively
simple instrumentation and I am certain that they well be indispensable in the laboratory
of every organic chemist in the near future” R B Woodward, 1973.
Chiral Stationary Phases
z
z
There are many chiral stationary phases
available (200+ on sale)
A very few have proven to be versatile
–
–
–
Polysaccharide-based phases (cellulose &
amylose, coated or immobilised on silica)
Antibiotic-based phases (vancomycin, teicoplanin
bonded to silica)
“Pirkle” phases (Whelk-O)
Polysaccharide phases
CH3
H
Cellulose
OR
O
OR
‘OJ’
(CHIRALCEL)
O
O
N
‘OK’
n
CH3
‘OG’
Cl
‘OF’
O
‘OB’
N
O
CH3
H
‘OA’
O
N
O
Amylose
OR
‘AD’
N
O
(CHIRALPAK)
n
CH3
H
O
OR O
CH3
H
O
RO
‘OD’
N
H
O
RO
CH3
O
CH3
CH
H
3
N
O
CHIRALCEL, CHIRALPAK, OD, OJ, AD and AS are registered trademarks of Daicel Chemical Industries, Ltd.
‘AS’
‘OC’
How do they work?
The phase takes up a helical structure
The chemical groups bonded to
the carbohydrate allow specific
interactions with the solutes. The
helix provides a chiral
environment in which the energy
of adsorption of one enantiomer
differs in comparison with the
other.
If this helical structure is modified, then the selectivity of the phase will also
be changed or even destroyed.
Antibiotic Phases
The antibiotic is
directly bonded to the
silica gel support
Pirkle Phases
Whelk-O
NH
Silica
O
Si
NO2
O
NO2
Use in Preparative Chromatography
z
According to Eric Francotte*, 90% of chiral
separations can be achieved using 4 of the
polysaccharide Chiral Stationary Phases (CSPs).
z
Almost all preparative and industrial scale
separations are carried out using these CSPs.
*
According to an analysis by Eric R. Francotte of Novartis, an estimated 1,300 CSPs have
been prepared and more than 200 are being sold. After reviewing about 1,000 racemic
separations, he also found, and reported at the Chiral Europe 2004 meeting, that about
90% of the mixtures could be separated by four CSPs: the cellulose derivatives
CHIRALCEL OD and CHIRALCEL OJ and the amylose derivatives CHIRALPAK AD and
CHIRALPAK AS--all made by Daicel Chemical Industries. C&E NEWS September 5, 2005
Volume 83, Number 36 pp. 49-53
Modes of Preparative Chromatography
Single injection
Multiple Overlapping Injections
Shave recycle
Increased
productivity
SMB
Increased complexity
Modes - Single Injection
Wasted time & solvent
Modes – Overlapping Injections
Response
6
4
2
0
0
2
4
6
8
10
12
Column Volumes
14
Modes – Shave Recycle (1)
Injector
Pump
Fraction
Collection
Column
Detector
Modes – Shave Recycle (2)
Injector
Pump
Fraction
Collection
Column
Detector
Modes – Shave Recycle (3)
Eluent
Injector
Pump
Fraction
Collection
Column
Detector
Modes – Shave Recycle (4)
Injector
Pump
Fraction
Collection
Column
Detector
Modes – Shave Recycle (5)
Eluent
Injector
Pump
Fraction
Collection
Column
Detector
Modes – Shave Recycle (5)
Injector
Pump
Column
Fraction
Collection
Detector
Modes – Steady State Recycle
Injector
Pump
Fraction
Collection
Column
Detector
Band Profile - SSR
Separation of methyl
and propyl parabens
Absorbance
Methyl
Cycle 41
Cycle 10
Propyl
Cycle 7
Cycle 4
Injection
0
1
2
Cycle 3
3
4
Time, min
5
6
SMB – basic principles (1)
Feed
column
Mobile Phase
A sample is injected in the centre of a stationary column
The two components move at different speeds and are separated
If we now move the column from right to left, at a speed halfway
between that of the solutes, they now move in different directions ...
SMB – basic principles (2)
column
Feed
Mobile Phase
The two solutes now move in different directions relative to a stationary
observer. If the column is very long, the bands will continue to separate.
SMB – basic principles (3)
column
Feed
Mobile Phase
The two solutes now move in different directions relative to a stationary
observer. If the column is very long, the bands will continue to separate.
If we continue to add sample at the centre, the components will continue
to separate...
SMB – basic principles (4)
column
Feed
Mobile Phase
This is clearly a continuous system, but there are problems.
It needs an infinite column length and some way to introduce and
remove the sample and the products.
We solve this by cutting the column into small segments and moving them
SMB – basic principles (5)
column
Feed
Mobile Phase
The feed and solvent inlets are now placed between the segments
and are moved each time a segment is moved from one end to the other
SMB – basic principles (6)
column
Feed
Mobile Phase
Mobile Phase
Products are removed by bleeding off a carefully calculated flow
at suitable exit points. This changes the velocity of the bands in
the column and forces the products to move toward the ports
This ensures that the column segments are clean before they are moved
and that the solvent can be recycled directly back through the system
SMB – basic principles (7)
Mobile Phase
Columns
SMB System - Start
Mobile
Phase pump
Feed Pump
Extract Pump
Raffinate Pump
Recycle
Pump
Switch 1
Mobile
Phase pump
Feed Pump
Extract Pump
Raffinate Pump
Recycle
Pump
Switch 2
Mobile
Phase pump
Feed Pump
Extract Pump
Raffinate Pump
Recycle
Pump
Switch 3
Mobile
Phase pump
Feed Pump
Extract Pump
Raffinate Pump
Recycle
Pump
Switch 4
Mobile
Phase pump
Feed Pump
Extract Pump
Raffinate Pump
Recycle
Pump
Switch 5
Mobile
Phase pump
Feed Pump
Extract Pump
Raffinate Pump
Recycle
Pump
Switch 6
Mobile Phase
pump
Feed Pump
Extract Pump
Raffinate Pump
Recycle
Pump
Switch 7
Mobile Phase
pump
Feed Pump
Extract Pump
Raffinate Pump
Recycle
Pump
Switch 8
Mobile
Phase pump
Feed Pump
Extract Pump
Raffinate Pump
Recycle
Pump
80 cm SMB system
Photo courtesy of
Aerojet Fine
Chemicals
SMB - Batch
Batch
SMB
Simple to develop
Simple Equipment
Solvent use high
Less expensive at small scale
Higher productivity
Lower solvent consumption
Higher product concentrations
Complex Equipment
Longer optimisation
Less expensive at large scale
Process Development
z
Simple concepts
z
Effects of overload
z
Computer simulations
Switch Time
Elapsed Time
T1
T2
T1 < Switch Time < T2
Switch Time
Range of Switch Time
T1
T2
Mass Overload
*
Range of Switch Time
Internal Profile
Internal Profile at Cycle P2-75 (290 nm)
Recycle
Raffinate
Feed
Eluent Extract
3.0E+03
2.5E+03
Area
2.0E+03
The internal concentration
profile is the most important tool
for optimisation of the SMB
process.
The x-axis is the position along
the column set; the y axis is the
concentration of each species
1.5E+03
1.0E+03
5.0E+02
0.0E+00
1
2
3
4
Column
5
6
Computer Simulation
z
z
z
Simulations are only as useful if the data that
is used for the adsorption isotherm is good.
With care, one can obtain useful starting
conditions from simulations, but the
separation usually needs optimisation
Isotherm data are often obtained from
overloaded batch separations
Loading Study – Troger’s base 1
Solubility: 40 g/l
Selectivity: 2.22
10 mg
0.4
0.35
Resolution: 2.77
0.3
Signal
0.25
Efficiency:
peak 1 : 1800 plates
peak 2 : 1200 plates
0.2
0.15
0.1
Asymmetry:
peak 1 : 1.07
peak 2 : 1.10
0.05
0
-0.05
0
1
2
3
4
Time (min)
5
6
7
8
Chiralpak® AS-Hexane / i-PA 9/1
Loading Study – Troger’s base 2
Solubility: 20 g/l
Selectivity: 2.54
1.5
40.5 mg
1.3
1.1
Efficiency:
peak 1 : 1200 plates
peak 2 : 900 plates
0.9
Signal
Resolution: 4.48
0.7
0.5
Asymmetry:
peak 1 : 1.04
peak 2 : 1.03
0.3
0.1
-0.1
0
2
4
6
8
Time (min)
10
12
14
Chiralpak® AD-MeOH
Loading Study – Troger’s base 3
Solubility: 80 g/l
8 mg
0.6
Selectivity: 1.88
0.5
Resolution: 1.90
Signal
0.4
Efficiency:
peak 1 : 1400 plates
peak 2 : 1000 plates
0.3
0.2
0.1
Asymmetry:
peak 1 : 1.22
peak 2 : 1.25
0
-0.1
0
1
2
3
4
Time (min)
5
6
7
8
Chiralpak® AD-Acetonitrile
Simulation Results
CHIRALPAK® AS / Hex-iPA
Feed flow &
concentration
Extract
concentration
Raffinate
concentration
ml/min & g/l
g/l
g/l
Production rate
kg rac/day
28.4 @ 30 g/l
5.3
10.5
1.23
CHIRALPAK® AD / MeOH
60 @ 18 g/l
4.0
7.94
1.55
CHIRALPAK® AD / ACN
13.7 @ 42 g/l
3.3
10.7
0.83
Experimental Results
Extract
purity
Raffinate
purity
ml/min & g/l
% ee
% ee
CHIRALPAK® AS / Hex-iPA
32 @ 30 g/l
99.8
98.7
1.38
CHIRALPAK® AD / MeOH
40 @ 18 g/l
98.0
100
1.04
CHIRALPAK® AD / ACN
22 @ 42 g/l
98.0
99.9
1.31
Feed flow &
concentration
Production rate
kg rac/day
Optimisation
z Selectivity
z Solvent
viscosity
z Solubility
z Example
: Guaiphenesin
Selectivity
Production (kg/day)
1.6
700
1.4
600
Cost
1.2
500
Solvent Use
1
400
0.8
Selectivity should be > 2 for
reasonable productivity
Selectivity for Guaiphenesin
is 2.3
300
0.6
200
0.4
Production
0.2
100
5 cm SMB Data
0
0
1
1.5
2
2.5
3
3.5
4
4.5
Selectivity
Project A:
α = 2.55
Productivity = 1.90 kg (en)/kg (CSP)/day (OD)
Project B:
α = 2.13
Productivity = 2.76 kg (en)/kg (CSP)/day (AS)
Project C:
α = 2.50
Productivity = 2.64 kg (en)/kg (CSP)/day (Library)
Viscosity
SMB Data
3.5
350
Productivity
300
2.5
250
α
2
Flow Rate
200
1.5
150
1
100
k’
0.5
50
0
0
0.5
1
Flow Rate
Productivity
3
Ethanol
Ethanol : Methanol (50:50)
Methanol
For Guaiphenesin the solvent
is 60% ethanol in hexane; a
viscosity of 0.98 – this is high
for SMB
0
1.5
Viscosity
Viscosity decrease increases column efficiency
and allows higher flow rates.
Solubility
SMB Data
Productivity (kg/kg/day)
1.8
Solubility should be in excess
of 30 - 40 g/l for high
productivity, low costs.
1.6
1.4
1.2
1
For guaiphenesin, the
solubility is low, at 20 – 25 g/l
0.8
0.6
0.4
0
20
40
60
80
Solubility (g/l)
100
120
Optimal Separation
6 x 10 x 1 cm CHIRALCEL OD (20 micron)
60% EtOH – hexane*
External Flows
Configuration 1:2:2:1
Feed Concentration (g/l) 30.0
Feed Flow (ml/min)
Internal Profile at Cycle P2-75 (290 nm )
El
Ext
Raf
Feed
Rec
3.0E+03
2.5E+03
Area
2.0E+03
Zone 1 (ml/min)
15.0
Extract (ml/min)
5.64
Raffinate (ml/min)
3.18
Switch Time (sec)
47.0
Pressure (bar)
1.5E+03
1.0E+03
0.78
1.57
2.35
Tim e (m in)
3.13
3.92
Productivity
Productivity{kg(en)
{kg(en)/ /kg
kg(CSP)
(CSP)/ /day}
day}
Eluent
EluentConsumption
Consumption{l/g(en)}
{l/g(en)}
4.70
40
% e.e.
Recovery
Raffinate:
> 99.6
97.8
Extract:
> 99.3
96.2
5.0E+02
0.0E+00
0.00
2.32
==
==
1.9
1.9
0.25
0.25
Economics
z
z
z
z
z
Case study of a high productivity separation
Outsourced
In-House
DCPIE – an intermediate for antifungals
Example = the synthesis of enantiopure
miconazole
Route
1. Isolation of enantiomer(s) by SMB from racemic DCPIE
H
N
N
OH
SMB
N
N
*
OH
Cl
Cl
Cl
Cl
DCPIE [1-(2,4-dichlorophenyl-2-(1-imidazoyl)ethanol]
2. Conversion of enantiomeric DCPIE to miconazole
Cl
Cl
N
N
*
OH
Cl
Cl
+
NaH
N
N
*
Cl
Cl
Cl
O
Cl
Cl
Development of SMB Separation
Analytical chromatogram:
D A D 1 C , S ig = 2 7 0 , 4 R e f= 4 0 0 ,8 0 (T : \ A G IL E N ~ 1 \ B A C K U P ~ 1 \ B A C K U P ~ 1 \ D C P I E 2 \ A N A L 5 U . D )
3.29 3
mAU
Selectivity = 9.16
1 7 .5
15
7 .5
1.646
5
6.78 8
10
to
excluded
1 2 .5
2 .5
0
0
1
2
3
4
5
6
Column: CHIRALPAK®AD®, 20 m, 10 x 1.0 cm
Mobile phase: 100% MeOH, Flow = 2 ml/min, P = 23 bar
Temperature: 25°C, Detection: UV at 290 nm
Vinj = 5 µl of 0.7g/l Racemic Solution
7
8
mi
Development of SMB Separation
Comparison of computer simulation and experimental results
Simulation
Experiment
(1 cm SMB)
Productivity (kg(en)/kg(CSP)/day
4.84
4.66
Solvent Consumption (l/g)
0.12
0.16
Extract Purity (%ee)
99.76
> 98
Raffinate Purity (%ee)
100
> 99
The experimental results showed that the computer simulation gave a
good indication of the separation conditions and likely performance of the
process using SMB. The productivity for this separation is high;
productivity between 1 and 2 is more normal for chiral separations suitable
for production purposes.
SMB Cost Assumptions
z
Processing on 15 MTA scale
z
Processing is outsourced to CMO
z
CM charge for 45 cm SMB unit $375k / month
z
SMB unit requires 4 weeks to clean between projects
z
Solvent cost $0.7/l
z
Solvent recovery 98% @ $0.1/l
z
CSP Cost $18000/kg
z
Product recovery 96%
z
Not possible to racemise the “wrong” enantiomer economically
SMB Size - Consequences
Column I.D.
(cm)
20
30
45
Time
Costs
Total
Processing
CSP
Solvent
(months)
($/kg)
($/kg)
($/kg)
($/kg)
9.6
4.2
2.0
168
108
72
3.9
3.9
3.9
17.9
17.9
17.9
189
130
95
The CSP and solvent costs per kg product are independent of scale. The
processing cost is a function of time and equipment charges. This cost
includes charges for cleaning and turn-around of a multi-use SMB unit.
Conclusions
z
z
z
SMB is a viable, large scale unit operation
Method development and optimisation is
simple
Purification costs are competitive with other
processes.