In-situ Solvent Recycling Process for Solid Phase Peptide Synthesis at Elevated Temperatures

Abstract

An improvement in of deprotection in solid phase peptide synthesis is disclosed. The method includes the steps of adding the deprotection composition in high concentration and small volume to the mixture of the coupling solution, the growing peptide chain, and any excess activated amino acid from the preceding coupling cycle; and without any draining step between the coupling step of the previous cycle and the addition of the deprotection composition for the successive cycle; and with the coupling solution at a temperature of at least 30° C.

Claims

1. A method of deprotection in solid phase peptide synthesis in which the improvement comprises: adding the deprotection composition in high concentration and small volume to the mixture of the coupling solution, the growing peptide chain, and any excess activated amino acid from the preceding coupling cycle; and without any draining step between the coupling step of the previous cycle and the addition of the deprotection composition for the successive cycle; and with the coupling solution at least 30° C.

2. A method according to claim 1 wherein the deprotection composition is an organic base

3. A method according to claim 1 using Fmoc solid phase peptide chemistry

4. A method according to claim 2 with the deprotection solution having a concentration of organic base of at least 50% by volume

5. A method according to claim 1 where the deprotection composition is added in an amount that is less than ⅓ of the volume of the coupling solution.

6. A method of deprotection in solid phase peptide synthesis in which the improvement comprises: adding the deprotection composition in high concentration and small volume to the mixture of the coupling solution, the growing peptide chain, and any excess activated amino acid from the preceding coupling cycle; and without any draining step between the coupling step of the previous cycle and the addition of the deprotection composition for the successive cycle which removes at least 50% of the volume of the previous cycle coupling solution; and with the coupling solution at a temperature of at least 30° C.

7. A method according to claim 6 wherein the deprotection composition is an organic base.

8. A method according to claim 6 using Fmoc solid phase peptide chemistry.

9. A method according to claim 6 with the deprotection solution concentration at least 50% by volume.

10. A method according to claim 6 where the deprotection composition is added in an amount that is less than ⅓ the volume of the coupling solution.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] FIG. 1 illustrates a traditional SPPS Cycle

[0007] FIG. 2 illustrates more recent SPPS Cycles for High Efficiency Solid Phase Peptide Synthesis (HE-SPPS)

[0008] FIG. 3 illustrates in-situ solvent recycling process for solid phase peptide synthesis.

DETAILED DESCRIPTION

[0009] This invention presents a novel process whereby the coupling and deprotection steps occur within the same solvent. In this process concentrated base is added directly to the resin coupling solution after a desired period of time for the coupling to occur. The deprotection step is then immediately started when the base is added. Therefore, the onset of the deprotection step is immediately after the coupling step without any time delay.

[0010] Additionally, only a small volume of base is required since it can use the solvent present from the coupling reaction. This requires a sophisticated reagent delivery system for the base that is accurate at very small volumes (0.5 mL) with rapid delivery. Typically, a 20% solution of base (piperidine) in solvent is used for the deprotection step. Excess base concentration can increase base-catalyzed side reactions and therefore significant solvent is required. This means that significant solvent can be saved from this process by adding concentrated base to the coupling solvent.

[0011] To demonstrate the effectiveness of this new process a batch of 24 peptides were assembled using an automated peptide synthesizer modified to perform the in-situ solvent recycling step during each cycle.

[0012] Materials and methods:

[0013] All peptides were synthesized using a LIBERTY BLUE™ PRIME™ system (CEM Corp., Matthews, N.C., USA) allowing for automated in-situ solvent recycling and evaporation based washing. The peptides were synthesized at 0.05 mmol scale with 10 equivalents of amino acid using CarboMAX™ coupling with amino acid/carbodiimide/ethyl 2-cyano-2-(hydroxyimino)acetate (AA/DIC/Oxyma) (1:2:1) based activation for 100 sec at 90° C. (E. Atherton, N. L. Benoiton, E. Brown, R. Sheppard and B. J. Williams, “Racemization of Activated, Urethane-protected Amino-acids by p-Dimethylaminopyridine. Significance in Solid Phase Peptide Synthesis,” J.C.S. Chem. Comm., pp. 336-337, 1981). ProTide resins (CEM Corp.) based on TentaGel® technology were used for synthesis with either a Rink Amide linker or a Cl-TCP(Cl) linker with unactivated loading of the first amino acid with DIEA at 90° C. for 5 min. The deprotection step was performed for 50 sec at 95° C. and initiated by adding 0.5mL of 50% pyrrolidine directly to the coupling solution. A single 1×4 mL wash was used in between the deprotection and coupling steps. Peptides were cleaved with Trifluoroacetic acid (TFA)/triisopropylsilane/water/2,2′-(ethylenedioxy)diethanethiol (TFA/TIS/H.sub.2O/DODt) (92.5:2.5:2.5:2.5) for 30 min at 38° C. using a RAZOR™ cleavage system (CEM Corp.).

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[0014] Results and discussion:

TABLE-US-00001 TABLE 1 Automated Sequential Batch Synthesis of 24 Peptides Resin UPLC Synthesis # Peptide Disease Area Used Purity Time  1 GRP Regulates RA 81 1:22 VPLPAGGGTVLTKMYPRGNHWAVGHLM-NH.sub.2 Gastrin Release ProTide  2 Glucagon Hypoglycemia RA 75 1:28 H-HSQGTFTSDYSKYLDSRRAQDFVQWLMNT-NH.sub.2 ProTide  3 Bivalirudin Blood thinner Cl-2-Cl- 71 1:05 H-fPRPGGGGNGDFEEIPEEYL-OH Trt  4 Angiotensin Vasoconstrictor Cl-2-Cl- 82 0:30 H-NRVYVHPF-OH Trt  5 PTH 1-34 Osteoporosis RA 70 1:43 H-SVSEIQLMHNLGKHLNSMERVEWLRKKLQDVHNF- ProTide NH.sub.2    6 Gonadorelin Fertility RA 91 0:35 pEHWSYGLRPG-NH.sub.2 ProTide  7 Triptorelin Breast Cancer, RA 73 0:35 pEHWSYwLRPG-NH.sub.2 Prostrate ProTide Cancer,  8 Liraglutide Diabetes RA 80 1:31 H-HAEGTFTSDVSSYLEGQAAK(.sub.Y-E- ProTide palmitoyl)EFIAWLVRGRG-NH.sub.2  9 Exenatide Diabetes RA 74 1:58 H- ProTide HGEGTFTSDLSKQMEEEAVRLFIEWLKNGGPSSGAPPPS- NH.sub.2 10 MOG (35-55) Multiple RA 71 1:05 H-MEVGWYRSPFSRVVHLYRNGK-NH.sub.2 Sclerosis ProTide 11 Secretin Osmoregulation RA 70 1:19 H-HDGTFTSELSRLRDSARLQRLLQGLV-NH.sub.2 ProTide 12 Teriparatide Osteoporosis RA 60 1:43 H-SVSEIQLMHNLGKHLNSMERVEWLRKKLQDVHNF- ProTide NH.sub.2 13 GLP-1 (7-37) Diabetes RA 74 1:34 H-HAEGTFTSDVSSYLEGQAAKEFIAWLVKGRG-NH.sub.2 ProTide 14 Magainin 1 Antibiotic RA 79 1:11 H-GIGKFLHSAGKFGKAFVGEIMKS-NH.sub.2 ProTide 15 Tetracosactide Adrenal Cortex RA 77 1:13 H-SYSMEHFRWGKPVGKKRRPVKVYP-NH.sub.2 stimulant ProTide 16 [Arg8]-Vasopressin Hormone (blood RA 94 0:32 H-CYFQNCPRG-NH.sub.2 vessel ProTide 17 Ubiquitin Protein RA ≧60 3:44 MQIFVKTLTGKTITLEVEPSDTIENVKAKIQDKEGIPPDQ signaling agent ProTide 18 Parasin I Antibiotic RA 87 0:59 H-KGRGKQGGKVRAKAKTRSS-NH.sub.2 ProTide 19 Dynorphin A Opioid RA 71 0:53 H-YGGFLRRIRPKLKWDNQ-NH.sub.2 Research ProTide 20 ACP Fatty Acid RA 92 0:32 H-VQAAIDYING-NH.sub.2 Synthesis ProTide 21 BAM 3200 Opioid RA 70 1:16 H-YGGFMRRVGRPEWWMDYQKRYGGFL-NH.sub.2 Research ProTide 22 HIV-TAT  (47-57) HIV/AIDS RA 93 0:31 Fmoc-YGRKKRRQRRR-NH.sub.2 Research ProTide 23 HIV-TAT (48-60) HIV/AIDS RA 88 0:39 Fmoc-GRKKRRQRRRPPQ-NH.sub.2 Research ProTide 24 Pramlintide Diabetes RA 72 1:52 KCNTATCATQRLANFLVHSSNNFGPILPPTNVGSNTY-- ProTide

[0015] All peptides synthesized in Table 1 gave the desired target as the major peak with a standard cycle time of 2 minutes and 58 seconds. The in-situ solvent recycling process allowed for 0.5mL of a concentrated pyrrolidine (BP 87° C.) solution to be added to the end of the coupling step (without draining). An advantage of this setup was that the deprotection immediately proceeded very close to the desired temperature (95° C.) because the coupling solution was already at 90° C. During the deprotection process a vacuum was applied and the pyrrolidine was evaporated and subsequently condensed in the waste container. This allowed only a single wash step (1×4 mL) to be required at the end of the deprotection step.

[0016] Total synthesis time for entire batch: 32.6 hours

[0017] This new process provided a significant reduction in standard cycle time (2 minutes 57 seconds) from (a)—elimination of the coupling drain time, (b)—elimination of the deprotection delivery time between steps, and (c)—elimination of the temperature ramp time for the deprotection step thereby allowing a shorter deprotection time to be used. Additionally, significant solvent savings were possible with the complete elimination of the deprotection solvent during each cycle.

[0018] In the drawings and specification there has been set forth a preferred embodiment of the invention, and although specific terms have been employed, they are used in a generic and descriptive sense only and not for purposes of limitation, the scope of the invention being defined in the claims.