Glycine‐rich proteins (GRPs) serve a variety of biological functions. Acanthoscurrin is an antimicrobial GRP isolated from hemocytes of the Brazilian spider Acanthoscurria gomesiana. Aiming to contribute to the knowledge of the secondary structure and stepwise solid‐phase synthesis of GRPs' glycine‐rich domains, we attempted to prepare G¹⁰¹GGLGGGRGGGYG¹¹³GGGGYGGGYG¹²³ GGY¹²⁶GGGKYK¹³²‐NH₂, acanthoscurrin C‐terminal amidated fragment. Although a theoretical prediction did not indicate high aggregation potential for this peptide, repetitive incomplete aminoacylations were observed after incorporating Tyr¹²⁶ to the growing peptide‐MBHA resin (Boc chemistry) at 60°C. The problem was not solved by varying the coupling reagents or solvents, adding chaotropic salts to the reaction media or changing the resin/chemistry (Rink amide resin/Fmoc chemistry). Some improvement was made when CLEAR amide resin (Fmoc chemistry) was used, as it allowed for obtaining fragment G¹¹³–K¹³². NIR‐FT‐Raman spectra collected for samples of the growing peptide‐MBHA, ‐Rink amide resin and ‐CLEAR amide resin revealed the presence of β‐sheet structures. Only the combination of CLEAR‐amide resin, 60°C, Fmoc‐(Fmoc‐Hmb)Gly‐OH and LiCl (the last two used alternately) was able to inhibit the phenomenon, as proven by NIR‐FT‐Raman analysis of the growing peptide‐resin, allowing the total synthesis of desired fragment Gly¹⁰¹–K¹³². In summary, this work describes a new difficult sequence, contributes to understanding stepwise solid‐phase synthesis of this type of peptide and shows that, at least while protected and linked to a resin, this GRP's glycine‐rich motif presents an early tendency to assume β‐sheet structures. © 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 92: 65–75, 2009.

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