Further applications of pentachlorophenyl active esters in the synthesis of peptides

Peptides Synthesis: Coupling of Pentachlorophenyl-active Ester Hydrochlorides of Di-and Tripeptides with N-Carbobenzoxy Amino Acids through Mixed Anhydride Method

“…We recently reported that pentachlorophenyl active esters of N-carbobenzoxy amino acids couple in satisfactory yields with amino acids and peptides C-protected by dicyclohexylamine, which can be conveniently removed by mild acid treatment at the end of the synthesis (6,7). It was observed that there was a definite increase in yields when N-protected pentachlorophenyl active esters of amino acids were coupled with di-or tripeptides instead of single amino acids C-protected by dicyclohexylamine.…”

Non‐covalent interactions in the protonation of diastereoisomeric dipeptides in aqueous solution

“…value (12), [ allow a better understanding of the effect of the lengthening of the side-chain on stereoselectivity by using the above approach. EXPERIMENTAL PROCEDURES Synthesis of L,o-ulunyl-phenylulanine (L,D-Ala-Phe) This peptide was synthesized by partially modifying the procedure reported for the L,Ldiastereoisomer (9). A suspension of Dphenylalanine (0.0 12 mol) and dicyclohexylamine (0.012mol) in methylene chloride was slowly added to a solution of N-carbobenzoxy-L-alanine (Z-L-alanine) pentachlorophenyl ester (10) (0.0102 mol) containing a catalytic amount (200 mg) of 2-hydroxypyridine in methylene chloride.…”

Peptides synthesis: Coupling of pentachlorophenyl active esters of N-carbobenzoxy amino acids and peptides to the pentachlorophenyl active ester hydrochlorides of amino acids

“…We recently reported that N-carbobenzoxy amino acid or peptide pentachlorophenyl esters couple in good yields with amino acids which are C-protected by salt formation with dicyclohexylamine (8). The salt protection from the resulting peptides was removed by mild acid treatment, thereby avoiding the alkaline treatment.…”

“…We now wish to report an interesting reaction sequence which we have found to be very reward-ing as a complementary approach to the method previously described (8). Using the new approach, we have been able to couple pentachlorophenyl active esters of amino acids or peptides with pentachlorophenyl active ester hydrochlorides of amino acids in satisfactory yields.…”