Epimerization of Cyclic Alanyl-Alanine in Basic Solutions

Munegumia, Toratane; Fujimoto, Takeshi; MichioTakada,; NozomiNagashima,

doi:10.13005/ojc/300103

Cited by 1 publication

(1 citation statement)

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“…40 This result could be attributed to the epimerization of cyclic dipeptides in basic solutions as already reported more than forty years ago. 41,42 A similar phenomenon is also observed for cyclic peptoids (N-substituted glycine analogues), for which each single CvO amide geometry displayed a single CvO amide peak 43 and in the presence of cis/trans isomers, multiple CvO amide peaks were observed. 43,44 Additionally, similar to the N-PBO-Cyclo (Ala-Ala) synthesis, a Cyclo(Gly-Gly)/tBuP 4 ratio of 1 : 0.5 yielded a polymer having the expected structure ( Table 2, P2-5) without transfer reactions.…”

Section: Resultssupporting

confidence: 60%

An alternative approach to create N-substituted cyclic dipeptides

et al. 2019

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N-Modified peptide backbones are promising peptidomimetics which offer several advantages in terms of improved biological activity and stability. They further allow the development of novel functional materials.However, the synthesis of N-substituted peptides is very challenging with the existing methods, particularly the synthesis of peptides with larger N-substituents. In this work, we are introducing a new method to create N-polyether substituted cyclic dipeptides via anionic ring-opening polymerization (AROP). Four different cyclic dipeptides with different hydrophobic functional groups were selected to create N-substituted cyclic dipeptides. Backbone amides -NHwere deprotonated with phosphazene bases to form nucleophilic initiators. Furthermore, the effect of different phosphazene bases (tBuP 4 and tBuP 2 ) and of the addition of a Lewis acid (i-Bu 3 Al) was studied in detail towards creating N-polyether-cyclic dipeptides bearing either hydrophobic poly(butylene oxide) chains, or hydrophilic linear polyglycidol chains, thanks to the polymerization of 1,2-epoxybutane and the polymerization followed by the deprotection of t-butyl glycidyl ether monomers, respectively. Moreover, we have demonstrated the possibility of avoiding the isomerization of cyclic dipeptides during the synthesis of N-substituted analogues depending on the synthetic approach. † Electronic supplementary information (ESI) available: 1 H, 13 C, 2D-HSQC, and 2D-HMBC NMR spectra, SEC traces and MALDI-ToF spectra. An additional scheme of plausible configurations. See

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Section: Resultssupporting

confidence: 60%