Application of tert-Butyl Disulfide-Protected Amino Acids for the Fmoc Solid-Phase Synthesis of Lactam Cyclic Peptides under Mild Metal-Free Conditions

MIL-101 magnetic nanocarrier for solid-phase delivery of doxorubicin to breast and lung cancer cells

An efficient strategy for passive delivery of doxorubicin (DOX) to the breast (MDA-MB-231) and lung (A-549) cancer cells is presented and compared with MCF-10A normal breast cells. Two versions of a peptide structure (linear and cyclic) have been designed and assessed. The molecular dynamic simulations in Material Studio2017 exhibited a higher adsorption capacity for L2 (cyclic version) compared with the adsorption capacity of L1 (linear version) on the PG surface by electrostatic interactions between guanidine of arginine and -OH of PG. The prepared final product based on iron oxide nanoparticles and MIL-101(Fe) (formulated as DOX@Fe3O4/MIL-101-(C,L)C[RW]3) is characterized and the drug content has been estimated. The release profiles revealed an ultra-fast stimulus-sensitive model in acidic media, which corroborates a pH-triggered release. The in vitro assessments disclosed that aggregation of nanocargo around the cancer cells and resulted toxicity are more than the neat DOX in the same dosage as DOX@Fe3O4/MIL-101-CC[RW]3. The obtained distinguished features lie in ability to utilize a biocompatible nanocargo structure to release an appropriate dose of DOX in a controlled manner in the cancer cell environment. Moreover, the functionalization of MIL-101 using cyclic and linear peptides and their comparison is one of the important features of this project.

Synthesis of Asp-based lactam cyclic peptides using an amide-bonded diaminodiacid to prevent aspartimide formation

Asp-based lactam cyclic peptides are considered promising drug candidates. However, using Fmoc solid-phase peptide synthesis (Fmoc-SPPS) for these peptides also causes aspartimide formation, resulting in low yields or even failure to obtain the target peptides. Here, we developed a diaminodiacid containing an amide bond as a β-carboxyl-protecting group for Asp to avoid aspartimide formation. The practicality of this diaminodiacid has been illustrated by the synthesis of lactam cyclic peptide cyclo[Lys9,Asp13] KIIIA7-14 and 1Y.

Complex cyclic peptide synthesis via serine/threonine ligation chemistry

Non-ribosomal cyclic peptides are abundant in natural sources, exhibiting attractive bioactivities and favorable pharmacological properties. Furthermore, their structural complexity renders them as attractive synthetic targets. A general task for cyclic peptide synthesis is the peptide cyclization. Compared to the traditional dehydration-based peptide macrolactamization, chemoselective peptide ligation provides an alternative, sometimes advantageous, strategy to cyclize peptides. Herein, we provide a series of structurally complex cyclic peptide examples whose total syntheses were achieved via peptide ligation-mediated peptide cyclization. The special features of these strategies for achieving the total synthesis are highlighted.