The reaction of an aromatic heterocycle with a proton is called a protonation. One of articles about this theory is 《Linear and cyclic peptides derived from p-aminobenzoic acid》. Authors are Langenbeck, Wolfgang; Weisbrod, Dieter.The article about the compound:cis-4-Aminocyclohexane carboxylic acidcas:3685-23-2,SMILESS:N[C@H]1CC[C@H](CC1)C(O)=O).Recommanded Product: cis-4-Aminocyclohexane carboxylic acid. Through the article, more information about this compound (cas:3685-23-2) is conveyed.
cf. CA 62, 13226b. The linear peptides N-carbobenzoxyglycyl-p-aminobenzoylglycyl-p-aminobenzoic acid (I), N-carbobenzoxy-ε-aminocaproyl-p-aminobenzoyl-ε-aminocaproic acid ethyl ester (II), and ε-aminocaproyl-p-aminobenzoyl-ε-aminocaproic acid (III) were obtained, using activated esters (method a) or the carbodiimide procedure (method b). The preparation of the cyclic peptides cyclo(ε-aminocapropyl-p-aminobenzoyl-ε-aminocaproyl-p-aminobenzoyl) (IV) and cyclo(11-aminoundecanoyl-p-aminobenzoyl) (V) was performed by cyclization of the corresponding linear peptides in diethyl phosphite with tetraethyl pyrophosphite as condensing agent. The formation of IV resulted probably from dimerization of the starting material. Because of the very small solubility of IV in all common solvents, it was impossible to determine the mol. weight p-Aminobenzoyl-ε-aminocaproic acid-HBr was prepared by hydrolysis of the N-carbobenzoxy compound To 4.1 g. N-carbobenzoxyglycyl-p-aminobenzoylglycine p-nitrophenyl ester in a mixture of 30 ml. tetrahydrofuran and 20 ml. Me2NCHO, a solution of 1.2 g. p-aminobenzoic acid and 0.35 g. NaOH in 10 ml. H2O was added. The mixture was refluxed 4 hrs. to yield 7.4% I, m. 297° (decomposition). For preparation of I using the mixed anhydride method, 3.3 g. N-carbobenzoxyglycyl-p-aminobenzoic acid, in 50 ml. tetrahydrofuran and 1.4 ml. Me3N, was treated with 1.31 ml. chlorocarbonic acid iso-Bu ester at -10°. To the reaction mixture, 2.75 g. glycyl-p-aminobenzoic acid-HBr in 20 ml. N NaOH was added and the mixture stirred 3 hrs. at 20° and 1 hr. at 40° to give 40% I. (Method a): To 3.8 g. carbobenzoxy-ε-aminocaproyl-p-aminobenzoic acid (VI) in 0.81 ml. pyridine and 50 ml. tetrahydrofuran, 1.35 ml. chlorocarbonic acid iso-Bu ester in 10 ml. tetrahydrofuran was added dropwise at -10° during 10 min., and stirring continued for 50 min. in the cold. ε-Aminocaproic acid ethyl ester-HCl (2 g.) in 10 ml. tetrahydrofuran and 0.81 ml. pyridine were added and the mixture was stirred 4 hrs. at 20° to give 28.8% II, m. 134°. (Method b) VI (3.8 g.) was dissolved in 50 ml. tetrahydrofuran, 2 g. ε-aminocaproic acid ethyl ester-HCl in 0.81 ml. pyridine and 2.1 g. dicyclohexylcarbodiimide in 5 ml. tetrahydrofuran added, and the mixture kept 24 hrs. at 20° to give 66.7% II. II (5.3 g.) was treated for 30 min. at 20° with 10 ml. HBr-HOAc to give 80.5% ε-aminocapropyl-p-aminobenzoyl-ε-aminocaproic acid ethyl ester-HBr (VII), m. 177-9°. VII (2.4 g.) was refluxed for 2 hrs. with 75 ml. Ba(OH)2 solution to give 7.2% III, m. 233° (decomposition). For cyclization, 1.324 g. ε-aminocaproyl-p-aminobenzoic acid-HBr (VIII) was dissolved in 1 l. diethyl phosphite, then 0.4 ml. pyridine and 4.85 ml. tetraethyl pyrophosphite added. The reaction mixture was stirred for 4 hrs. at 140° under N. Diethyl phosphite was distilled in vacuo, and the residue heated for 1 hr. with 100 ml. H2O and 1 l. MeOH. A white precipitate of linear oligopeptides with high mol. weight was filtered off, and 900 ml. H2O added to the filtrate, whereby further linear oligomers were precipitated, and removed by filtration. The filtrate was passed through an ion exchanger (Wofatit KPS 200, anionic, Wofatit L 150, cationic) and concentrated to 50 ml. in vacuo to give 22.6% IV, m. ∼380° (decomposition). Cyclization of VIII in the presence of tetraethyl pyrophosphite and 1.4 g. imidazole gave 23.2% IV. 11-Aminoundecanoyl-p-aminobenzoic acid-HBr (IX) [prepared in 94% yield from N-carbobenzoxy-11-aminoundecanoyl-p-aminobenzoic acid by hydrolysis with HBr-AcOH, m. 236-8° (decomposition)] (1.604 g.) in l. diethyl phosphite in the cold was treated with 0.4 ml. pyridine and 4.85 ml. tetraethyl pyrophosphite to give 23.6% V, m. 218-20°. Cyclization of IX with equivalent amounts of tetraethyl pyrophosphite and imidazole gave 21.7% IV. N-Carbobenzoxy-p-aminobenzoyl-ε-aminocaproic acid (3.8 g.) was hydrolyzed for 30 min. at 20° with 15 ml. HBr-AcOH to give 57.4% p-aminobenzoyl-ε-aminocaproic acid-HBr, m. 160°. N-Carbobenzoxy-11-aminoundecanoyl-p-aminobenzoic acid was hydrolyzed with HBr-AcOH to give 64.6% raw 11-aminoundecanoyl-p-aminobenzoic acid, m. 204-7°. p-Aminobenzoic acid was dissolved in AcOH and hydrogenated with PtO2 at 20° and atm. pressure. After 1/3 of the theoretical amount of H was absorbed, addnl. PtO2 was added. This procedure was repeated several times. When 80% of the theoretical amount of H was absorbed, the hydrogenation was stopped, and the reaction mixture worked up to give 20.9% cis-hexahydro-p-aminobenzoic acid.
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Reference:
Synthesis and Crystal Structure of a Chiral C3-Symmetric Oxygen Tripodal Ligand and Its Applications to Asymmetric Catalysis,
Chiral lanthanide(III) complexes of sulphur–nitrogen–oxygen ligand derived from aminothiourea and sodium D-camphor-β-sulfonate