Use of cyclopentyl ester protection for aspartic acid to reduce base catalyzed succinimide formation in solid-phase...

A study was conducted to determine the effect of amino acid sequence and aspartyl protecting group on the rate of base catalyzed succinimide formation in the solid-phase synthesis of aspartyl peptides. The peptides H-Ala-Asp-Gly-Phe-OH and H-Ala-Asp-Leu-Phe-OH were synthesized by the solid-phase method with cyclopentyl or benzyl protection for the beta-carboxyl of aspartic acid. The results showed that the cyclopentyl ester was notably less susceptible to succinimide formation by treatment with tertiary amine than was the benzyl ester, and that the difference could have significant consequences for the synthesis of the large peptides which contain reactive sequences such as Asp-Gly.