Passage
Solid-phase peptide synthesis is normally carried out on a resin bathed multiple times in dimethylformamide (DMF) -a toxic, polar, aprotic solvent-which poses an environmental problem because a large amount of toxic solvent waste is created. Cyclic carbonates such as propylene carbonate (PC) and ethylene carbonate (EC) are nontoxic, polar, aprotic solvents that could be used as an alternative to DMF.Compounds 1 and 2 are modified L-amino acids. They were coupled to form Compound 3, a dipeptide, which was then deprotected to yield Compound 4 (Figure 1) .
Figure 1 Synthesis of Compound 4To determine the effect that solvent type and temperature have on the synthesis of this peptide, the nontoxic solvents PC and EC as well as the toxic solvent DMF were each used in separate syntheses of Compound 4 at different temperatures. The reaction solvent was also used to rinse the resin. Table 1 shows the results of these syntheses.Table 1 Results from the Synthesis of Compound 4
The successful synthesis of Compound 4 using nontoxic solvents encouraged researchers to pursue the synthesis of a larger, biologically active peptide. Bradykinin, a vasodilator containing nine amino acids (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) , was synthesized using the same solid-state peptide synthesis protocol used to synthesize Compound 4. Separate syntheses were done using either DMF or PC, and the purity of bradykinin from each synthesis was analyzed by high-performance liquid chromatography (HPLC) (Figure 2) .In each chromatogram, peak 1 has the same retention time as commercially obtained bradykinin, and the other peaks correspond to impurities. In chromatogram A, the impurity has a similar retention time to the product peak whereas the impurity peaks in chromatogram B have distinct retention times compared to the product peak.
Figure 2 HPLC of synthetic bradykinin: (A) synthesis in DMF; (B) synthesis in PC
Adapted from S. B. Lawrenson et al., "The greening of peptide synthesis." Green Chem. ©2017 The Royal Society of Chemistry.
-A peptide bond is formed in bradykinin synthesis when the amino group of arginine reacts with:

Question

Passage
Solid-phase peptide synthesis is normally carried out on a resin bathed multiple times in dimethylformamide (DMF) -a toxic, polar, aprotic solvent-which poses an environmental problem because a large amount of toxic solvent waste is created. Cyclic carbonates such as propylene carbonate (PC) and ethylene carbonate (EC) are nontoxic, polar, aprotic solvents that could be used as an alternative to DMF.Compounds 1 and 2 are modified L-amino acids. They were coupled to form Compound 3, a dipeptide, which was then deprotected to yield Compound 4 (Figure 1) .

Figure 1 Synthesis of Compound 4To determine the effect that solvent type and temperature have on the synthesis of this peptide, the nontoxic solvents PC and EC as well as the toxic solvent DMF were each used in separate syntheses of Compound 4 at different temperatures. The reaction solvent was also used to rinse the resin. Table 1 shows the results of these syntheses.Table 1 Results from the Synthesis of Compound 4

The successful synthesis of Compound 4 using nontoxic solvents encouraged researchers to pursue the synthesis of a larger, biologically active peptide. Bradykinin, a vasodilator containing nine amino acids (Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg) , was synthesized using the same solid-state peptide synthesis protocol used to synthesize Compound 4. Separate syntheses were done using either DMF or PC, and the purity of bradykinin from each synthesis was analyzed by high-performance liquid chromatography (HPLC) (Figure 2) .In each chromatogram, peak 1 has the same retention time as commercially obtained bradykinin, and the other peaks correspond to impurities. In chromatogram A, the impurity has a similar retention time to the product peak whereas the impurity peaks in chromatogram B have distinct retention times compared to the product peak.

Figure 2 HPLC of synthetic bradykinin: (A) synthesis in DMF; (B) synthesis in PC
Adapted from S. B. Lawrenson et al., "The greening of peptide synthesis." Green Chem. ©2017 The Royal Society of Chemistry.
-A peptide bond is formed in bradykinin synthesis when the amino group of arginine reacts with:

Quizplus · Accepted Answer

11ecba2d_1298_7a55_a3bf_d13ea9ac8bc2_MD0008_00 Amino acids are made up of an amino group, a carboxyl group, and a side chain, all bonded to the same carbon atom (known as the α-carbon). Peptides contain two or more amino acids bonded together. The amino group of one amino acid reacts with the carboxyl group of another amino acid to form a peptide bond. The passage shows that the amino acid arginine (Arg, R) is located at both the N- and C-termini of bradykinin. The amino group of the arginine at the C-terminal end reacts with the carboxyl group of the adjacent amino acid, phenylalanine (Phe, F), to form a peptide bond. (Choice A) Anhydride groups do not react with amines to form peptide bonds, nor is this functional group present in any of the 20 common amino acids. (Choice C) An amide is formed during peptide bond formation rather than reacting with an amino group to form a peptide bond. (Choice D) Although some amino acids contain hydroxyl groups in their side chains, this functional group does not react with an amine to form a peptide bond. Educational objective: Peptides contain two or more amino acids bonded together. The amino group of one amino acid reacts with the carboxyl group of another amino acid to form a peptide bond.

Passage Solid-Phase Peptide Synthesis Is Normally Carried Out on a Resin