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Synthesis of Peptides with α,β‐Dehydroamino Acids, V. Coupling experiments with C‐Terminal Dehydrophenylalanine and Dehydroalanine Residues
Author(s) -
Makowski Maciej,
Rzeszotarska Barbara,
Kubica Zbigniew,
Pietrzyński Grzegorz,
Hetper Jacek
Publication year - 1986
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.198619860603
Subject(s) - tripeptide , chemistry , dehydroalanine , peptide , carbodiimide , stereochemistry , dipeptide , acylation , yield (engineering) , residue (chemistry) , adduct , glycine , amino acid , peptide synthesis , organic chemistry , biochemistry , catalysis , materials science , metallurgy
N ‐Protected model dipeptides of C‐terminal ( Z )‐ΔPhe and ΔAla couple with glycine esters after activation with either diphenyl phosphorazidate (DPPA), N ‐cyclohexyl‐ N′ ‐[2‐( N ‐methylmorpholinio)ethyl]carbodiimide p ‐toluenesulfonate (WSC), N,N′ ‐dicyclohexylcarbodiimide + 1‐hydroxybenzotriazole (DCC + HOBt), or the mixed anhydride (MA) with isobutyl chlorocarbonate to give in good or mostly moderate yields the ( Z )‐ΔPhe‐containing tripeptides 1 – 9 and ΔAla‐containing tripeptides 11 – 19 , respectively. In the MA and DPPA methods, further acylation products 20a – d are formed to a great extent, expecially during the ΔAla peptide syntheses. ( E )‐TFA‐Gly‐ΔPhe and Gly‐OtBu, irrespective of the activation method, afford mixtures of ( Z )‐ and ( E )‐tripeptides 1 and 10 with small amounts of the ( E )‐isomer 10 . Addition products to the ΔAla double bond were isolated. They are azidotripeptides 21a – 1 formed if the DPPA method is used. An adduct 22 from tripeptide and HOBt arises from the WSC + HOBt method. In the MA method, loss of the ΔAla residue is observed and X‐Gly‐Gly‐OY 23a and b are obtained. The previously N‐deprotected tripeptides 1 and 11 were condensed with Boc‐Gly‐OSu to yield the tetrapeptides 24 and 25 .