(2R)-2-[[(9H-Fluoren-9-ylmethoxy)carbonyl]amino]-2-methyl-9-decenoic Acid, is a stable antimicrobial peptide, that can be isolated from the venom of wild bee Lasioglossum laticeps.
Olefinic alpha-methyl amino acid for peptide stapling. Upon incorporation of this amino acid into a peptide, along with another of the same or derivative with a different length of the olefinic side chain, the two can be ′stapled′ via a ring closing metathesis reaction with Grubb′s catalyst (product # 579726). The resulting stapled peptide macrocycle has been shown to stabilize the alpha-helical structure of peptides, which can lead to favorable biological characteristics such as increased proteolytic stability and cellular uptake.
reaction type: Fmoc solid-phase peptide synthesis
1. 1.55 kg (1.0 eq.) of 37-amino-2-methyl-dec-9-enoic acid hydrochloride (XIII) was suspended in 22 L of water and polished and filtered to remove traces of D-BPB hydrochloride.
2. Methyl tert-butyl ether was added and the aqueous product layer was extracted once with methyl tert-butyl ether.
3. The aqueous product layer was added again and 7 L of tetrahydrofuran was added.
4. 20% aqueous sodium carbonate (2.75 eq.) was added to the mixture followed by Fmoc-OSu (0.89 eq.).
5. The reaction was carried out at 20-25 °C, maintaining the pH at 8.5-9.0 by adding additional amounts of 20% sodium carbonate solution until the reaction was complete.
6. Adjust the pH of the mixture to 2.0-2.5 with concentrated hydrochloric acid.
7. The tetrahydrofuran is removed by distillation and methyl tert-butyl ether is added.
8. Separate the layers and wash the organic layer with water 3 times.
9. The organic layer is concentrated in vacuum and azeotropically distilled with methyl tert-butyl ether.
10. The crude oily substance is dissolved in methyl tert-butyl ether, cyclohexylamine (1.10 eq.) is slowly added, and the pH is adjusted to 8.5-9.0.
11. The slurry was stirred at 20-25 °C for 3 h. The solid product salt (XIV) was isolated by filtration.
12. The solids were rinsed twice with methyl tert-butyl ether and the wet cake was reloaded into a clean reactor.
13. The wet cake was recrystallized with tetrahydrofuran and methyl tert-butyl ether to improve purity.
14. The solid salt is suspended in methyl tert-butyl ether and water and the pH is adjusted to 2.0-2.5 with 25% sulfuric acid.
15. The organic product layer was washed with water until no cyclohexylamine remained.
16. The organic layer was concentrated and azeotropically distilled with hexane to a loose oil. 17.
17. The product (IIa) was crystallized from chloroform and hexane and purged dry with 1.0 cfm nitrogen at <0 °C. The product (IIa) was then purged dry at <0 °C with 1.0 cfm nitrogen.
Yield: 1.12 kg, 41.5% yield.
Recrystallization procedure:
18. Acetonitrile (23 mL/10 g of raw material ((R)-Ala-Ni-BPB(XI) in oil)) was added to the crude product and the mixture was heated to 70 °C and held for 30 min, then cooled to 20 °C. The mixture was purified with aqueous nitrogen.
19. The mixture was filtered and the solids were washed with acetonitrile (5 mL) and methyl tert-butyl ether (8.5 mL) to give a crystalline product.
[1] Patent: US2014/128581, 2014, A1. Location in patent: Paragraph 0087; 0156; 0157
![9-Decenoic acid, 2-[[(9H-fluoren-9-ylmethoxy)carbonyl]amino]-2-methyl-, (2R)-, compd. with cyclohexanamine (1:1)](/CAS/20211123/GIF/1609117-04-5.gif)
