Synth�se du N-ac�tyl-L-s�ryl-L-tyrosyl-L-s�ryl-L-m�thionyl-?-L-glutamate de benzyle et de peptides apparent�s

Dendritic Poly-[N-(2-Hydroxyethyl)-L-Glutamine] as Potential Drug Carrier

Dendritic poly-[ N-(2-hydroxyethyl)-L-glutamine] (PHEG) with different molecular weights were synthesized by aminolysis of dendritic poly-(γ-benzyl-L-glutamate) (PBG), which was obtained by polymerization of the corresponding N-carboxyanhydride (NCA) with poly(amido amine) (PAMAM, starburst®) of the fourth generation as initiator. Dynamic light scattering (DLS) was used to determine the size of the polymeric carriers and to compare the dendritic polymer to the linear analogue. The body distribution and blood clearance of 125 I-radiolabelled linear and dendritic PHEG with similar molecular weight were investigated in female BALB/c mice.

[N6-dipeptide derivatives of the N12-ribosyl-indolo[2,3-a]carbazole]

N6-derivatives of N12-ribosyl-indolo[2,3-a]pirrolo[3,4-c]carbazole-5,7-dione are synthesized as potential antitumor agents, in which an atom of N6-pyrrole part of heterocycle is included into the dipeptide residual of the general formula >N6-(CH2)n-CO-Ala/βAla-OMe (n = 2 or 3). These compounds are derived by reacting of 13-methyl-12-(2,3,4-three-O-acetyl-β-D-ribopyranosyl)indolo[2,3-a]furano[3,4-c] carbazole-5,7-dione with dipeptides, having an unreplaced N-amino end-group, in DMF at 130°C, wherein the nitrogen atom of peptide amino group replaces oxygen O6 in furan ring of heterocycle and is embedded in imide nitrogen atom of pyrrole N6. The ability of the obtained compounds to inhibit growth of SKOV3 human ovarian carcinoma cells was studied, only derivative with radical >N6-(CH2)3-CO-L-Ala-OMe showed cytotoxic activity with an inhibitory concentration of IC50 = 8 μM.

Concise total synthesis of the thiazolyl peptide antibiotic GE2270 A

The potent antibiotic thiazolylpeptide GE2270 A was synthesized starting from N-tert-butyloxycarbonyl protected valine in a longest linear sequence of 20 steps and with an overall yield of 4.8 %. Key strategy was the assembly of the 2,3,6-trisubstituted pyridine core by consecutive cross-coupling reactions starting from 2,6-dibromo-3-iodopyridine. The complete Southern fragment was installed by Negishi cross-coupling of 3-zincated 2,6-dibromopyridine at the terminal 2-iodothiazole of a trithiazole (87 %). The substituent at C-6 representing the Northern part of the molecule was introduced in form of the truncated tert-butyl 2-bromothiazole-4-carboxylate after metalation to a zinc reagent by another Negishi cross-coupling (48 %). Decisive step of the whole sequence was the macrocyclization to a 29-membered macrolactam, which was conducted as an intramolecular Stille cross-coupling occurring at C-2 of the pyridine core and providing the desired product in 75 % yield. The required stannane was obtained by amide bond formation (87 %) between a complex dithiazole fragment representing the Eastern part of GE2270 A and a 3,6-disubstituted 2-bromopyridine. Final steps included attachment of a serine-proline amide dipeptide to the Northern part of the molecule (65 %), formation of the oxazoline ring and silyl ether deprotection (55 % overall).

Design and synthesis of all diastereomers of cyclic pseudo-dipeptides as mimics of cyclic CXCR4 pentapeptide antagonists

The four diastereomers of 2,5-bis[(3-guanidino)propyl]-1-[3-(4-hydroxyphenyl)propionyl]-7-(2-naphthylacetyl)-1,4,7-triazacycloundec-9-en-3-one (-) and of 2,5-bis[(3-guanidino)propyl]-1-(4-hydroxyphenylacetyl)-7-(2-naphthylacetyl)-1,4,7-triazacycloundec-9-en-3-one (-) were synthesized by a divergent methodology from l- and D-glutamic acids. The 11-membered ring core was made by ring closing metathesis of linear bis(allylamines), and the guanidyl functions were introduced by a simultaneous double Mitsunobu reaction using bis(Boc)guanidine. These compounds were designed to mimic cyclic pentapeptide FC131 (c[Gly-D-Tyr-Arg-Arg-Nal]).

Poly-L-glutamic acid derivatives as vectors for gene therapy

This paper describes the synthesis and evaluation of biodegradable derivatives of poly-L-glutamic acid as suitable vectors for gene therapy. When mixed with DNA the new polymers self assemble and form polyelectrolyte complexes. The formation of the complexes and determination of their stability towards disruption by serum albumin was monitored by Ethidium bromide (EtBr) fluorescence spectroscopy. All polymers were able to form complexes and their size, determined by photon correlation spectroscopy, was between 84.5+/-2 nm and 96. 7+/-1.6 nm, depending on the type of polymer and the charge ratio. All complexes were stable towards serum albumin. The results from the biodegradability tests, using tritosomes, show that the polymers are biodegradable and the rate of degradation is influenced by the number of charged groups in the side chains. Haemolysis and red blood cell (RBC) agglutination were assessed and compared to poly(L-lysine) (pLL) and polyethyleneimine (pEI). RBC agglutination was monitored with optical microscopy. Results show that the new polymers are less toxic than pLL and pEI. Preliminary transfection studies show that the polymers are suitable vectors for gene delivery.

L-Glutamic acid and L-lysine as useful building blocks for the preparation of bifunctional DTPA-like ligands

Bisalkylation of suitably protected L-glutamic acid and L-lysine derivatives with tert-butyl N-(2-bromoethyl)iminodiacetate 2, followed by deprotection of the omega functional group affords N, N-bis[2-[bis[2-(1, 1-dimethylethoxy)-2-oxoethyl]amino]ethyl]-L-glutamic acid 1-(1, 1-dimethylethyl) ester 4 and N2,N2-bis[2-[bis[2-(1, 1-dimethylethoxy)-2-oxoethyl]amino]ethyl]-L-lysine 1,1-dimethylethyl ester 7. Such compounds feature a carboxylic or an amino group, respectively, which are available for conjugation with a suitable partner via formation of an amide bond. The conjugates, which can be prepared in this way, contain a chelating subunit in which all five acetic residues of DTPA are available for the complexation of metal ions. Direct bisalkylation of glycine with 2 promptly gives N, N-bis[2-[bis[2-(1,1-dimethylethoxy)-2-oxoethyl]amino]ethyl]glycine 11. The latter allows to achieve conjugates in which the central acetic group of DTPA is selectively converted into an acetamide.

Novel constrained CCK-B dipeptoid antagonists derived from pipecolic acid

A new series of 4-substituted pipecolic acid derivatives was prepared and incorporated into dipeptoids. The resulting products behave as moderately potent CCK-B antagonists but their constrained structure and its comparison with structurally related compounds yield valuable information about the conformational requirements for optimal recognition of the CCK-B receptor by antagonists.