INTRODUCTION
VIP (vasoactive intestinal peptide), a peptide hormone, has been implicated in a number of biological processes including: increasing digestive system motility, stimulating pepsinogen secretion, controlling the mammalian circadian timekeeping machinery, regulating prolactin secretion, and causing vasodilation. One problem with synthesis of VIP is aspartimide formation during Fmoc deprotection. Aspartimide formation occurs most frequently in peptides containing Asp followed by Asn(Trt), Gly, Thr, or Ser. The use of 5% piperazine with 0.1 M HOBt for the deprotection solution can readily reduce the amount of aspartimide formation during microwave peptide synthesis providing the VIP peptide in high crude purity compared to the conventional method.
Figure 1: Aspartimide Formation