Solvent effects on coupling yields during rapid solid-phase synthesis of CGRP(8-37) employing in situ neutralization

• Published in: The journal of peptide research Vol. 65; no. 1; pp. 84 - 89
• Main Authors: Taylor, C.K., Abel, P.W., Hulce, M., Smith, D.D.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.01.2005
• Subjects: calcitonin gene-related peptide; Calcitonin Gene-Related Peptide - chemical synthesis; Calcitonin Gene-Related Peptide - chemistry; Chromatography, High Pressure Liquid; coupling yield; DMF; NMP; Peptide Fragments - chemical synthesis; Peptide Fragments - chemistry; peptide-resin; solvation; solvent; Solvents - chemistry
• ISSN: 1397-002X; 1399-3011
• DOI: 10.1111/j.1399-3011.2004.00200.x

:  The success of solid‐phase peptide synthesis is often dependent upon solvation of the resin and the growing resin‐bound peptide chain. We investigated the relationship between solvent properties and solvation of the resin and peptide‐resin in order to obtain satisfactory coupling yields for the rapid solid‐phase peptide synthesis, using butyloxycarbonyl‐(Boc)‐amino acid derivatives, of human‐α‐calcitonin gene‐related peptide(8‐37) (CGRP(8‐37)). Solvation of (p‐methylbenzhydrylamine)copoly(styrene–1% divinylbenzene (DVB) (resin) and resin covalently bound to the fully protected amino acid sequence of CGRP(8‐37) (peptide–resin) was correlated to solvent Hildebrand solubility (δ) and hydrogen‐bonding (δh) parameters. Contour solvation plots of δh vs. δ revealed maximum solvation regions of resin and peptide–resin. Maximum resin solvation occurred with N‐methylpyrrolidinone (NMP), NMP : dimethylsulfoxide (DMSO) (8 : 2) and DMSO. Inefficient solvation of the peptide–resin occurred with these solvents and resulted in poor syntheses with average coupling yields of 78.1, 88.9 and 91.8%, respectively. Superior peptide–resin solvation was obtained using dimethylacetamide (DMA) and dimethylformamide (DMF), resulting in significantly higher average coupling yields of 98.0 and 99.5%, respectively. Thus, the region of maximum peptide–resin solvation shifts to solvents with higher δh values. DMF provided the most effective peptide–resin solvation and was the only solvent from which CGRP(8‐37) was obtained as a single major product in the crude cleaved material.