Synthesis of peptides with α,β‐dehydroamino acids, V. coupling experiments with C‐terminal dehydrophenylalanine and dehydroalanine residues

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 activati…

SYNTHESIS OFt-BUTOXYCARBONYL AND BENZYLOXYCARBONYL AMINO ACID AMIDES

Synthesis of peptides with α,β‐dehydroamino acids, I. synthesis of N‐benzyloxycarbonyl and N‐trifluoroacetyl dipeptides of dehydroalanine and dehydrophenylalanine

Condensation of amides of N-(benzyloxycarbonyl)- and N-(trifluoroacetyl)amino acid with pyruvic and phenylpyruvic acid yields, in the presence of p-toluenesulfonic acid as a catalyst, N-(benzyloxycarbonyl)- and N-(trifluoroacetyl)dehydro dipeptides with C-terminal Δ Ala and ΔPhe, respectively (Table 2 and 3). Synthese von Peptiden mit α,β-Dehydroaminosauren, I. - Synthese von N-(Benzyloxycarbonyl)-und N-(Trifluoracetyl) dipeptiden von Dehydroalanin und Dehydrophenylalanin Die Kondensation von Nα-(Benzyloxycarbonyl)- und Nα-(Trifluoracetyl)aminosaureamiden mit Brenztrauben- und Phenylbrenztraubensaure in Gegenwart von p-Toluolsulfonsaure als Katalysator fuhrt zu N-(Benzyloxycarbonyl)- und N-…

Synthesis of Peptides with α,β-Dehydroamino Acids, II. Synthesis oftert-Butyloxycarbonyldipeptides of Dehydroalanine and Dehydrophenylalanine

Condensation of amides of Boc-amino acids3) with pyruvic acid leads to Boc-dipeptides 1 – 3 of dehydroalanine and 1-Boc-5-alkyl-2-methyl-4-oxo-2-imidazolidinecarboxylic acids 8 – 10. The amides, however, do not condense with phenylpyruvic acid. Boc-dipeptides of dehydroalanine (1 – 3) and dehydrophenylalanine (4 – 7) are synthesized using (Boc)2O and dehydrodipeptides with a free unmasked N-terminal amino group. Synthese von Peptiden mit α,β-Dehydroaminosauren, II1). – Synthese von tert-Butyloxycarbonyldipeptiden von Dehydroalanin und Dehydrophenylalanin2) Die Kondensation von Boc-Aminosaureamiden3) mit Brenztraubensaure fuhrt zu Boc-Dipeptiden 1 – 3 des Dehydroalanins und 1-Boc-5-alkyl-2-m…

Synthesis of peptides with α,β‐dehydroamino acids, III. Debenzyloxycarbonylation and detrifluoroacetylation of dehydroalanine and dehydrophenylalanine peptides

The removal of amino protecting groups from a series of twelve model Z-3) or TFA-dipeptides of dehydroalanine and (Z)-dehydrophenylalanine was investigated. During this deprotection, peptides with Δ Ala are prone to side reactions to a higher extent than those with Δ Phe. Therefore it is interesting to note that from the Δ Ala peptides, the Z group can be split off in preparative manner with HCO2NH4 in the presence of Pd C (Table 4). Synthese von Peptiden mit α,β-Dehydroaminosauren, III.– Debenzyloxycarbonylierung und Detrifluoracetylierung von Dehydroalanin- und Dehydrophenylalanin-Peptiden An einer Serie von zwolf Z-3) oder TFA-Modellpeptiden mit Dehydroalanin und (Z)-Dehydrophenylalanin …