Microwave-Enhanced Solid Phase Peptide Synthesis. Jonathan M. Collins Bioscience Division CEM Corporation

Transcription

1 Microwave-Enhanced Solid Phase Peptide Synthesis Jonathan M. Collins Bioscience Division CEM Corporation

2 Microwave SPPS Reaction Vessel

3 Standard Microwave Fmoc SPPS Parameters Deprotection Time Temperature Bubbling Enhanced 30 seconds (5)* Deprotection, 40ºC (25ºC)* Coupling, N 2 and 3 minutes (15)* Cleavage 80ºC Reactions (25ºC)* N 2 Coupling Time Temperature Bubbling 5 minutes (60)* 80ºC (25ºC)* N 2 *Typical Conventional Parameters

4 Galanin Synthesis Conditions GWTLNSAGYLLGPQQFFGLM-NH 2 Scale: 0.10mmol w/ MBHA Rink Amide Resin, 0.59meq/g. (Novabiochem) Enhanced Deprotection, Coupling, and A= Conventional B= Microwave Cleavage Reactions Reaction Reagents Time Max Temp. (ºC) Deprotection 20% Piperidine / DMF 3 min 21=A, 75=B Coupling HBTU/HOBt/DIEA 0.9/1/1, x10 excess 4 min Cleavage Reagent K 18 min 21=A, 75=B 38=A and B

5 GWTLNSAGYLLGPQQFFGLM-NH 2 Conventional (Purity = < 10 %) Microwave (Purity = 84.8%)

6 Angiogenin Conditions ENGLPVHLDQSIFRRP Enhanced Deprotection, Coupling, and Scale: 0.25mmol w/ Pro-Chlorotrityl Resin, 0.61 meq/g. (Anaspec) Cleavage Reactions Reaction Reagents Time Max Temp. (ºC) Deprotection 20% Piperidine / DMF 3 min 75 Coupling HBTU/DIEA 0.9/1, x4 excess 4 min Cleavage TFA/TIS/H2O 18 min 75 38

7 ENGLPVHLDQSIFRRP Crude purity = 86.7% Total synthesis time = 5 hours

8 Proinsulin C-peptide EAEDLQVGQVELGGGPGAGSLQPLALEGSLG Conditions Scale: 0.25mmol w/ MBHA Rink Amide Resin, 0.60meq/g. (Novabiochem) Enhanced Deprotection, Coupling, and Cleavage Reactions Reaction Reagents Time Max Temp. (ºC) Deprotection 20% Piperidine / DMF 3 min 75 Coupling PyBOP/DIEA 0.9/2, x6 excess 4 min Cleavage TFA/TIS/H2O 18 min 75 38

9 EAEDLQVGQVELGGGPGAGSLQPLALEGSLG Crude purity = 75.0% Total synthesis time = 10 hours

10 Microwave Peptide Synthesis I. Microwave Application to SPPS II. Microwave SPPS Enhanced A. Racemization Deprotection, Coupling, and B. Aspartimide Cleavage formation Reactions C. (δ-lactam formation) - Arginine D. Difficult peptides (microwave vs. conventional) E. Phosphopeptide synthesis

11 Aggregation The peptide backbone, coupling reagents, and solvent (DMF) are all polar and will attempt to align with the alternating electric field of the microwave. At 2450MHz, 1 alteration ~ 10-9 s. Random motion of the chain breaks up aggregation

12 A. Racemization during SPPS Conventional synthesis has shown racemization can be an issue with His and Cys residues Enhanced Deprotection, Coupling, and Cleavage Reactions Aspartimide Formation of Asp-Gly segments can lead to racemization of Asp and other side products Microwave coupling is performed with a 5-min. reaction, at 80 C maximum temperature

13 Racemization of Cysteine H N SH H O OH N R 3 R 1 R 2 α-carbon proton is susceptible to direct proton abstraction by tertiary amines during coupling 1 Preactivation can significantly elevate racemization levels for Cys 1 Han et al. (1997) J. Org. Chem. 62,

14 Racemization of Histidine H H N N τ H O π N OH π-nitrogen is closer to the α-carbon and sufficiently basic to abstract a proton τ -nitrogen more accessible and easier to protect (Trt) 1 Racemization at higher temperatures is an issue during activation state 1 Harding, S.J.; Jones, J.H.; Sabirov, A.N.; Samukov, V.V.; J. Pept. Sci.; 5,

15 Aspartimide Formation in SPPS N H O O X NH N H O O N Nu N H Nu O NH O N H O NH O Nu Hydrolysis O O N H O OH NH N H O NH OH

16 Investigation of Racemization during Microwave SPPS Research Peptide VYWTSPFMKLIHEQCNRADG-NH 2 Consists of all 20 amino acids including Cys, His C-terminal Asp-Gly Segment for maximum aspartimide potential and racemization of Asp

17 VYWTSPFMKLIHEQCNRADG-NH 2 Unacceptable levels of racemization of Asp, Cys, and His residues Addition of 0.1M HOBt during deprotection reduced Asp racemization Addition of HOBt to the coupling solution had no benefit

18 Reducing Aspartimide Formation Piperazine vs. Piperidine N N N Piperazine pka = 9.8 Piperidine pk= 11.1 Piperazine has a slower Fmoc removal rate, but has shown decreased levels of aspartimide formation Piperazine is a non-controlled substance and less toxic and odorous than piperidine Tregear, G., Macris, M., Mathieu, M.N., Wade, J.D.; Pept. Sci., 7,

19 VYWTSPFMKLIHEQCNRADG-NH 2 Microwave energy allows for complete Fmoc removal in 3- minutes w/ piperazine Piperazine substantially reduced racemization of Asp

20 Tertiary Amines - SPPS Coupling N Enhanced Deprotection, Coupling, N and Cleavage NMM ReactionsTMP (Collidine) DIEA pka = 10.1 pka = 7.41 O N pka = 7.43 Hindered amines used for reducing racemization

21 VYWTSPFMKLIHEQCNRADG-NH 2 NMM elevated racemization levels compared to DIEA Possibly due to slower coupling rates TMP significantly reduced Cys racemization Selection of base does effect His racemization

22 VYWTSPFMKLIHEQCNRADG-NH 2 Lower coupling temperatures (55ºC) significantly reduces His racemization Cys moderately effected Racemization limited to activated ester state Elevated temperatures up to 80ºC do not increase racemization of Cys and His already incorporated on a peptide chain

23 C. δ-lactam formation of Arginine Fmoc Enhanced Deprotection, Coupling, and NH NH Cleavage Reactions NHR H N H O Act Fmoc H N O N NH NHR Competitively occurs with peptide bond formation Can be a significant problem for difficult Arg couplings

24 δ-lactam formation of Arginine ABRF 1992 Peptide: GVRGDKGNPGWPGAPY Lactam formation of arginine causes major deletion during synthesis

25 GVRGDKGNPGWPGAPY Synthesis Conditions 1. Non-microwave 2. 20% Piperidine / DMF 3. HBTU/DIEA 4. Tyr(tBu)-Wang Resin (0.88meq/g) Significant Arg deletion

26 GVRGDKGNPGWPGAPY Synthesis Conditions 1. Microwave 2. 20% Piperidine / DMF 3. HBTU/DIEA 4. Tyr(tBu)-Wang Resin (0.88meq/g) Significant Arg deletion Significant aspartimide formation 18 co-elute w/ product and del(arg)

27 PEG vs. PS Based Resins PEG Based PS Based From

28 GVRGDKGNPGWPGAPY Synthesis Conditions 1. Microwave 2. 5% Piperazine w/ 0.1M HOBt / DMF 3. HBTU/DIEA 4. PAL-ChemMatrix Resin Elimination of Arg deletion Elimination of aspartimide formation

29 1-42 ß-amyloid DAEFRHDSGYEVHHQKLVFFAEDVGSNKGAIIGLMVGGVVIA MW = Difficult peptide to synthesize Difficult peptide analyze Synthesis PAL-PEG-PS Resin ; 0.2meq/g (Applied Biosystems) 20% Piperidine in DMF HBTU/DIEA activation

30 1-42 ß-amyloid DA - EFRHDSGYEV - HHQKLVFFAE - DVGSNKGAII - GLMVGGVVIA 9.6% Purity 37.2% Crude Yield 68.8% Purity 40% Crude Yield Conventional Microwave Microwave Energy increased purity Total synthesis time of 19 hours

31 KPVSLSYRCPCRFFESHVARANVKHLKILNTPNCALQIVARLKNNNRQV CIDPKLKWIQEYLEKALNK MW = mmol synthesis Lys-NovSyn Resin Chemokine SDF-1a 20% Piperidine w/ 0.1M HOBt in DMF HBTU/DIEA activation Crude Purity ~ 50% Total synthesis time of 35 hours

32 SPS of Polyamides Containing Pyrrole and Imidazole Amino Acids Polyamides containing (Im) and (Py) amino acids have affinity for DNA comparable to naturally occuring DNA binding proteins FmocHN N N O OH FmocHN N O OH Fmoc HN O OH Fmoc-Im-OH (N-methylimidazole) Fmoc-Py-OH (N-methylpyrrole) Fmoc-γ-OH (g-aminobutyric acid) "hairpin" motif

33 SPS of Polyamides Containing Pyrrole and Imidazole Amino Acids Im-Im-Py-Py-γ-Im-Py-Py-Py-β-Dp MW = (Dp = dimethylaminopropylamine) (β = beta-alanine) Synthesis 0.1mmol synthesis w/ ß-Ala CLEAR Resin; (0.52meq/g) 20% Piperidine in DMF HBTU/DIEA activation Pre-activation performed (Fmoc-Im-OH) soluble in DMF w/ HBTU/DIEA

34 SPS of Polyamides Containing Pyrrole and Imidazole Amino Acids Im-Im-Py-Py-γ-Im-Py-Py-Py-β-Dp MW = % Crude Purity Total Synthesis Time of 5 hours Conventionally 180 minute couplings required 1 1 Org. Lett.(2001), 3, 8, 1201

35 Phosphopeptide Synthesis Phosphoamino acids derivatives allow for their direct incorporation during synthesis Enhanced Deprotection, and eliminate Coupling, the need and for Cleavage Reactions difficult post-synthetic phosphorylation Difficult to couple and make subsequent couplings difficult Fmoc-Ser(PO(OBzl)OH)-OH

36 Phosphopeptide Synthesis Test Peptide: EIVPN(pS)VEQK-OH Conventional Deprotection = 5, 15 minutes (20% Piperidine in DMF) Coupling = 60 minutes (HBTU/DIEA, 5-fold excess) Microwave (Max T = 80 C for both) Deprotection = 30 seconds, 3 minutes (20% Piperidine in DMF) Coupling = 5 minutes (HBTU/DIEA, 5-fold excess)

37 Conventional Deprotection Conventional Coupling Microwave Deprotection Microwave Coupling Conventional Deprotection Microwave Coupling Phosphoserine residues can be coupled faster and more efficiently with microwave Higher temperatures during deprotection, even at 50ºC (separate experiment) can cleave phosphate groups [-79 mass]

38 Summary Microwave energy can be used to successfully enhance both the deprotection and coupling reactions Enhanced Deprotection, Coupling, and longer sequences Cleavage Reactions Complete cycle times of 25 minutes are attainable even for Piperazine can be used effectively as a replacement for piperidine Cysteine and Histidine require special conditions for racemization free couplings Phosphopeptide couplings are substantially accelerated with microwave

39 Programming Liberty Step 1 / 5: Operation Cycles

40 Programming Liberty Step 1 / 5: Operation Cycles Every operation cycle is fully customizable

41 Programming Liberty Step 1 / 5: Operation Cycles Easy access to the reaction vessel for manual additions or removal at programmable pauses

42 Programming Liberty Step 2 / 5: Enter a Sequence

43 Programming Liberty Step 2 / 5: Enter a Sequence Ideal for precious reagents; ex. phosphoamino acids No priming required

44 Programming Liberty Step 3 / 5: Set Conditions for Sequence Multiple cycles can be applied to an individual sequence

45 Ease of Use Running a Peptide Step 4 / 5: Load method into 1 12 position and check volume usage calculator Step 5 / 5: Press START!

46 C. Serviceability Automated Valve and Sensor Verification