Microwave‐Assisted Solid‐Phase Peptide Synthesis Utilizing N‐Fmoc‐Protected (α‐aminoacyl)benzotriazoles

Abstract

A novel microwave-assisted solid-phase peptide synthesis utilizing N-Fmoc-protected(alpha-aminoacyl)benzotriazoles was applied in the preparation of tri-, tetra-, penta-, hexa-, and heptapeptides in 71% average crude yield.

N‐Fmoc‐Protected(α‐Dipeptidoyl)Benzotriazoles for Efficient Solid‐Phase Peptide Synthesis by Segment Condensation

“…Readily available N ‐Fmoc‐Protected( α ‐aminoacyl)benzotriazoles 1a–d (16,18) were coupled with unprotected chiral amino acids l ‐Ala, l ‐Met, l ‐Phe, and racemic mixtures dl ‐Ala and dl ‐Met in aqueous acetonitrile (CH 3 CN:H 2 O/2:1) in the presence of Et 3 N at 20 °C for 1 h afforded N α ‐Fmoc‐protected‐dipeptides 2a–f , ( 2a + 2a′ ), and ( 2b + 2b′ ) (77–87%) isolated without chromatography (Scheme 1, Table 1) a .…”

Fluorescent labeling of peptides on solid phase

“…In a similar manner, microwave-assisted SPPS was achieved utilized the appropriate N-acylbenzotriazoles derived from Fmocprotected L-Met, L-Trp, L-Phe, L-Leu, L-Pro and Gly prepared by our previously published procedures. 34 The mild synthetic conditions allowed utilization of the unprotected indole-NH of L-Trp, and no complications were observed with L-Met or any other of the amino-N-protected amino acids utilized.…”

“…Solid phase peptide synthesis, microwave-assisted as optimized previously in our laboratory, 34 enables efficient acylation of NH 2groups on solid phase by the benzotriazole activated fluorogenic substrates 2, 4, 5, 7, 9. We used 2 or 5 to couple the fluorophore directly to diverse peptides.…”

“…Compound 10 was synthesized using microwave-assisted SPPS conditions. 34 After initial removal of the Fmoc protecting group, free Rink resin-NH 2 was coupled with 4 in DMF under microwave irradiation for 10 min at 70 • C. The second coupling was performed with the (N a -Fmoc-aminoacyl)benzotriazole reagent derived from Fmoc-L-Ala, finally the desired peptide was cleaved from the resin to produce peptide amide 10 (26%) (Scheme 3, Table 1, Fig. 1).…”

“…33 Recently we have also prepared tri-, tetra-, penta-, hexa-, and heptapeptides in 71% average crude yields by microwave-assisted solid phase peptide synthesis utilizing (N a -Fmoc-aminoacyl)benzotriazoles. 34 These easily obtained, chirally stable, and moisture insensitive reagents acylate NH 2 -peptideresins without using coupling agents or additives, thus avoiding side reactions and epimerization. 34 We now report the efficient fluorescent labeling of peptides on solid phase by acylation with benzotriazole activated derivatives of (i) coumarin-3-ylcarboxylic acid and 7-methoxycoumarin-4-ylacetic acid and (ii) coumarin-3-ylcarbonyl (Cc) and 7methoxycoumarin-4-ylacetyl (Mca) labeled lysines.…”