Multiple synthesis by the multipin method as a methodological tool

The multipin method of peptide synthesis is demonstrated as a potent methodological tool, where large numbers of comparative studies can be performed concurrently. Two studies are presented. In each study, the test peptides were simultaneously synthesized, and the products examined by high throughput ion spray mass spectrometry and reverse‐phase HPLC. In the first study, comprising 24 experiments, peptides 1 (AELFSTHYLAFKEDYSQ‐NH2) and 2 (LKDFRVYFREGRDQLWKGPG‐NH2) were prepared using Fmoc‐Axx/BOP/HOBt/NMM (100: 100: 100: 150 mM) and Fmoc‐Axx/HATU/HOAt/NMM (100: 100: 100: 150 mM) with 60.90 and 120 min coupling times. The two reagent combinations were found to give comparable results. The second study compared the N‐terminal coupling of Fmoc‐Asn‐OH, Fmoc‐Asn(Mbh)‐OH, Fmoc‐Asn(Mtt)‐OH, Fmoc‐Asn(Tmob)‐OH and Fmoc‐Asn(Trt)‐OH in the synthesis of seven test peptides: 3, NVQAAIDYIG‐cyclo(Kp); 4, NTVQAAIDYIG‐cyclo(KF); 5, NRVYVHPFNL; 6, NRVYVHPFHL: 7, NEAYVHDAPVRSLN: 8, NQLVVPSEGLYLIYSQVLFK. 9, NPNANPNANPNA. A total of 33 experiments were performed. Peptides 3 and 4 were selected to highlight the effect of steric bulk of each Asn derivative on coupling efficiency. Reagent efficiency, as measured by target peptide purity, was as follows: Fmoc‐Asn(Tmob)‐OH > Fmoc‐Asn‐OH > Fmoc‐Asn(Mtt)‐OH = Fmoc‐Asn(Trt)‐OH > Fmoc‐Asn(Mbh)‐OH.