All the peptides were synthesized manually on 2-chlorotrityl chloride resin by employing standard Fmoc/tBu solid-phase peptide synthesis protocol. Fmoc-L-amino acid or Fmoc-D-amino acid building blocks were coupled to the resin using the HBTU, HOBt, and DIPEA in DMF. Fmoc protecting groups were removed by treatment with 20% (v/v) piperidine in DMF after each coupling. After the complete extension of the desired peptide sequence, the side chain-protected peptides were detached from the resin by treating the peptidyl resin with a mixture of TFE/acetic acid/DCM [2:1:7 (v/v/v)]. The crude-protected peptides were separated by filtration from the resin and precipitated with chilled diethyl ether. The crude masses of protected peptides were dried under vacuum and cyclized using HOAt and DIC in an anhydrous DMF/DCM [1:4 (v/v)] mixture. Following the head-to-tail cyclization, the protecting groups were removed with a cocktail of TFA/water/TIS [95:2.5:2.5 (v/v/v)], and the crude peptide was precipitated with ice-cooled diethyl ether. After multiple ether washes, the obtained crude mass was redissolved in acetonitrile/water (1:1 v/v with 0.5% TFA), and the solution was lyophilized to obtain the crude peptide.