ABSTRACT
The synthesis of the novel pentagastrin seco-CBI conjugate 3, which is based on the highly cytotoxic antitumor antibiotic (+)-duocarmycin SA (1), is reported. A key step in the synthesis is the palladium-catalyzed carbonylation of aryl bromide 7 to give the benzyl ester 16, which is transformed into the new seco-CBI derivative 21 bearing a carboxylic acid ester moiety. Subsequent transformation of 21 into an activated ester followed by the introduction of beta-alanine and tetragastrin led to the new pentagastrin drug 3 that contains a peptide moiety for targeting cancer cells expressing CCK-B/gastrin receptors.
Subject(s)
Antineoplastic Agents/chemical synthesis , Indoles/chemistry , Indoles/chemical synthesis , Pentagastrin/analogs & derivatives , Pentagastrin/chemistry , Antineoplastic Agents/chemistry , Catalysis , Cell Proliferation/drug effects , Drug Delivery Systems , Duocarmycins , Esters/chemistry , Molecular Structure , Palladium/chemistry , Pentagastrin/chemical synthesis , Pyrroles/chemistry , Receptor, Cholecystokinin B/biosynthesis , Receptor, Cholecystokinin B/drug effectsABSTRACT
Cleavage and kinetic studies have been carried out using commercially obtained H-Tyr(tBu)-5-(4'-aminomethyl-3',5'-dimethoxyphenoxy)valeric acid-TentaGelS (H-Tyr(tBu)-4-ADPV-TentaGelS) and H-Tyr (tBu)-4-ADPV-Ala-aminomethyl-resin (H-Tyr(tBu)-4-ADPV-AM-resin) prepared from commercially available resin and loaded with commercially available Fmoc-4-ADPV-OH amide anchor. Cleavage with pure trifluoroacetic acid (TFA) gave the intermediate H-Tyr-4-ADPV-NH2, which was then degraded to H-Tyr-NH2, and cleavage with TFA/dichloromethane (1:9) yielded H-Tyr-4-ADPV-NH2 which could be isolated in preparative amounts. Cleavage reactions with 15N-labelled H-Ala-4-ADPV-(15N)-Gly-AM-resin yielded the intermediate H-Ala-4-ADPV-NH2, which contained no 15N as demonstrated by 1H-NMR. The analysis of the commercial Fmoc-4-ADPV-OH amide anchor showed the presence of Fmoc-4-ADPV-4-ADPV-OH as an impurity in high amounts. This dimeric anchor molecule is the cause of formation of the anchor-linked peptide intermediate obtained during the cleavage from the resin. The particularly high acid-lability of the amide bond between the two ADPV moieties was utilized to synthesize sidechain and C-terminally 4-ADPV protected pentagastrin on a double-anchor resin, and to cleave it using 5% trifluoroacetic acid in dichloromethane. This method may offer a new way for the synthesis of protected peptide amides with improved solubility to be used in fragment condensation.
Subject(s)
Peptides/chemistry , Peptides/chemical synthesis , Amides/chemical synthesis , Amides/chemistry , Amino Acid Sequence , Binding Sites , Dimerization , Fluorenes , Indicators and Reagents , Kinetics , Methods , Molecular Structure , Pentagastrin/chemical synthesis , Pentagastrin/chemistry , Resins, Synthetic , Solubility , ValeratesABSTRACT
Frequency-domain fluorescence spectroscopy was employed to examine the decays of tryptophan in Boc-Trp-Met-Asp-Phe-NH2 (donor) and (Formula: see text) (donor-acceptor pair). The efficiency of energy transfer in the thiopeptide amounted to 60%. The measured dispersion of fluorescence decay times was used to recover the donor-acceptor distance distribution. The parameters of the Gaussian distance distribution obtained for this peptide (r, the mean distance (9 A); hw, the halfwidth (25 A)) indicate the lack of a distinct favorable conformation.
Subject(s)
Pentagastrin/analogs & derivatives , Sulfhydryl Compounds , Energy Transfer , Pentagastrin/chemical synthesis , Protein Conformation , Spectrometry, Fluorescence/methods , Sulfhydryl Compounds/chemical synthesis , TryptophanABSTRACT
The large-scale synthesis of the pentapeptide Boc-beta-Ala Trp-Met-Asp-Phe-NH2 is described and a convenient procedure for purification of the crude peptide will be reported.
Subject(s)
Pentagastrin/chemical synthesis , Chemical Phenomena , Chemistry , Chromatography, Paper , Pentagastrin/analysisABSTRACT
Nine new pentagastrin analogs containing a free or protected alpha-aminooxy acid at the N-terminus were synthesized stepwise. Analogs containing leucyl, norleucyl, norvalyl, L- and D-2-aminodecanoyl residues instead of methionyl residue were also prepared. The peptides were synthesized by the active ester method with subsequent removal of the protecting groups. The purification of the end products was performed by crystallization or column chromatography on silica gel.
Subject(s)
Pentagastrin/analogs & derivatives , Amino Acid Sequence , Chromatography, Gel , Methods , Pentagastrin/chemical synthesisABSTRACT
Twenty-seven new pentagastrin analogs containing free or protected aminooxy acids at the N-terminus and D-2-aminooxy-3-phenyl-propionic acid, L-(4-chlorophenyl)glycine, L- and D-phenylglycine, or L- or D-cyclohexyglycine instead of the C-terminal L-phenylalanine and analogs extended by aminooxyacetic acid at the C-terminus, were synthesized stepwise. The end products were purified by chromatography on DEAE-cellulose or silica gel.
