Solid-Phase Synthesis of Cyclic Peptides

Synthesis and Structure–Activity Relationship of Cytotoxic Marine Cyclodepsipeptide IB‐01212 Analogues

“…The Fmoc-protecting group was removed with 20 % of piperidine in DMF during 20 min and piperidine/DBU/toluene/DMF (5:5:20:70) for 10 min to assure complete removal. [28,29] Then, the Fmoc-Aaa2-OH (2 equiv) was carried out with an equimolar amount of PyBOP/ HOAt and a double amount of DIEA in DMF for 1 h. This method ology is one of the most effective for the coupling of FmocAaa-OH on NMeAaa because it combines a reactive standalone coupling reagent (PyBOP) [30] with an excellent leaving group (HOAt). [31] Furthermore, PyBOP is relatively inexpensive compared to PyAOP, [32] which is the phosphonium salt derived from HOAt.…”

Analysis of 9-fluorenylmethoxycarbonyl (FMOC) loading of solid-phase synthesis resins by gas chromatography

“…DBU deprotection of resin-bound FMOC groups, without adverse effects on other functionality, has been recently reported. 5,7 GC analysis of a deprotection mixture of 2% DBU and 10 mg/mL FMOC-EA in DMF confirmed that dibenzofulvene was the sole product of the deprotection without 9-fluorenone as a contaminant (see Figure 4b). A standard curve was prepared using anthracene as internal standard (cf.…”

“…Recently, the non-nucleophilic amidine 1,8-diazabicyclo [5.4.0]undec-7-ene (DBU) has been utilized as an alternative to the more commonly employed base piperidine for FMOC removal. 5,7 The objective of the present study was to develop a high-throughput protocol for quantitation of FMOC loading which is less labor intensive than UV methods. In particular, the use of gas chromatography (GC) in conjunction with an internal standard was examined as an alternative to standard UV-based methods.…”

Synthesis of a cyclic peptide library based on the somatostatin sequence using the backbone amide linker approach

“…followed by strong acid cleavage [5,6]. Both methods requires the use of scavengers to remove protecting groups with considerable workup.…”