One of the most frequently encountered side reactions affecting Asp-Gly in Fmoc SPPS is aspartimide formation, resulting from a ring closure between the N of the α-carboxy amide bond and the β-carboxy side chain of the Asp with the loss of ester protecting group in the presence of piperidine. We encountered this problem during the microwave assisted synthesis of a group of precursor peptides carrying a C terminal Ala-Tyr-Asp-Gly motif. We explored a range of deprotection conditions containing various chemicals (eg. Piperidine, piperazine, HOBT, oxymapure), resins (eg. Tentagel-R-PHB-Gly-(DMB)) and a side chain protected dipeptide (eg. Fmoc-Asp(OtBu)-(Dmb)Gly-OH) during synthesis to prevent aspartimide formation. In our hands none of the conditions we attempted were successful in preventing aspartimide formation during microwave assisted synthesis, highlighting the current need for a simple and practical approach to minimize aspertimide formation under microwave assisted peptide synthesis. Our results indicate that a mixture of Piperidine and Oxymapure in DMF as deprotecting agent successfully prevent aspertimide formation during manual peptide synthesis.