Influence of heterochirality on the structure, dynamics, biological properties of cyclic(PFPF) tetrapeptides obtained by solvent-free ball mill mechanosynthesis

Cyclic tetrapeptides c(Pro-Phe-Pro-Phe) obtained by the mechanosynthetic method using a ball mill were isolated in a pure stereochemical form as a homochiral system (all L-amino acids, sample A) and as a heterochiral system with D configuration at one of the stereogenic centers of Phe (sample B). The structure and stereochemistry of both samples were determined by X-ray diffraction studies of single crystals. In DMSO and acetonitrile, sample A exists as an equimolar mixture of two conformers, while only one is monitored for sample B. The conformational space and energetic preferences for possible conformers were calculated using DFT methods. The distinctly different conformational flexibility of the two samples was experimentally proven by Variable Temperature (VT) and 2D EXSY NMR measurements. Both samples were docked to histone deacetylase HDAC8. Cytotoxic studies proved that none of the tested cyclic peptide is toxic.


Figure S2 .
Figure S2.Flash chromatogram of the crude mixture after the reaction of ball grinding•for 3 hours of Pro-Phe-Pro-Phe•HCl with TBTU and DIPEA and washing with water.

Figure S5 .
Figure S5.A crystal packing diagram of (a) c(Pro-Phe-Pro-Phe) (sample A) and (b) c(Pro-Phe-Pro-D-Phe) (sample B).The views along the b-axis are shown above, while the views along the a-axis are shown below.

Figure S11 .
Figure S11.NMR HSQC 1 H-15 N (a) and HSQC 1 H-13 C (b) spectra of cPFPF-A, CD3CN (Homochiral).Prefix S means form of peptide A with 2-fold symmetry and prefix U means unsymmetrical form of A.

Figure S15 .
Figure S15.600 MHz 1 H NMR spectra of N-H region of sample A (left) and sample B (right) dissolved in chloroform-d.

Figure S16 .
Figure S16.Crystal structure of histone deacetylase 8 in complex with trapoxin A.

Table S7 .
Relative conformers energies with population at 298 K for sample A after DFT calculations at the B3LYP/6-311+G(d,p)/PCM(H2O) level of theory.

Table S8 .
Relative conformers energies with population at 298 K for sample B after DFT calculations at the B3LYP/6 311+G(d,p)/PCM(H2O) level of theory.