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The Z isomer of the new constrained analog of the anticancer drug octreotide, where L,L-cystine is replaced by 4,5-dehydro-L,L-diaminosuberic acid, was prepared by solid-phase ring-closing metathesis. NMR study ascertained that this molecule is conformationally very close to the parent octreotide and remains unaffected by the enzymatic pool of the human serum for more than 30 h. © 2005 Bentham Science Publishers Ltd.

Cyclen derivs., as coordinating ligands, have recovered considerable interest for the development of diagnostic and therapeutic drugs, mimicking the binding site of metalloproteins. We demonstrate that the on-resin redn. of head-to-tail cyclotetrapeptides, anchored to a solid support by the side-chain of a trifunctional amino acid, is an efficient synthetic strategy. The proposed approach leads to the cyclen scaffold still bound to the resin, ready for further decorations.

The synthesis of a new biotin derivative, the (CO) reduced N-aminohexyl biotinamido derivative, designed to be serum biotinidase resistant, and its conjugation to the chelator DOTA through an amide bond at one of the four carboxymethyl chains are described. The 90Y-labeled conjugate was able to bind avidin at different Av/conjugate molar ratios with good results. The preclinical results indicate that this new biotin–DOTA conjugate is a good candidate for pretargeted diagnosis and therapy of tumors.

Glycopeptides of hMOG(30-50) containing a glucosyl moiety on the side-chains of Asn, Ser or Hyp at position 31 were synthesised. Antibody titres to hMOG(30-50) and to its glucoderivatives were measured by ELISA in sera of patients affected by different neurological diseases. Anti-hMOG(30-50) antibodies were detected only using the glycopeptide [Asn31(N-Glc)]hMOG(30-50).

Peptides with increased lipophilicity can cross cell membranes more easily and have longer half-life times. For these reasons, the synthesis of enantiomerically pure Fmoc-protected lipidic alpha-amino acids is a relevant goal. Schiff bases originating from the reaction between the two enantiomers of 2-hydroxypinan-3-one with Gly-OtBu were alkylated with a series of long alkyl halides. Diastereomeric excesses were determined by reversed-phase HPLC, under conditions carefully chosen for such lipophilic substrates.

A limited set of novel octreotide dicarba-analogues with non-native aromatic side chains in positions 7 and/or 10 were synthesized. Their affinity toward the ssts1-5 was determined. Derivative 4 exhibited a pan-somatostatin activity, except sst4, and derivative 8 exhibited high affinity and selectivity toward sst5. Actually, compound 8 has similar sst5 affinity (IC50 4.9 nM) to SRIF-28 and octreotide. Structure-activity relationships suggest that the Z geometry of the double-bond bridge is that preferred by the receptors. The NMR study on the conformations of these compounds in SDS(-d25) micelles solution shows that all these analogues have the pharmacophore beta-turn spanning Xaa7-D-Trp8-Lys9-Yaa10 residues. Notably, the correlation between conformation families and affinity data strongly indicates that the sst5 selectivity is favored by a helical conformation involving the C-terminus triad, while a pan-SRIF mimic activity is based mainly on a conformational equilibrium between extended and folded conformational states.

We describe synthesis, conformational studies, and binding to the five somatostatin receptors (sst 1-5) of a few analogues of the cyclic octapeptide octreotide (1), where the disulfide bridge was replaced by a dicarba group. These analogues were prepared by on-resin RCM of linear hepta-peptides containing two allylglycine residues; first- and second-generation Grubbs catalyst efficiencies were compared. The C=C bridge was hydrogenated via two different methods. Binding experiments showed that two analogues had good affinity and high selectivity for the sst5 receptor. Three-dimensional structures of the active analogues were determined by (1)H NMR spectroscopy. Conformation-affinity relationships confirmed the importance of D-Phe(2) orientation for sst2 affinity. Moreover, helical propensities well correlates with the peptide sst5 affinity. The presence of the bulky aromatic side chain of Tyr(Bzl)(10) favored the formation of a 3(10)-helix and enhanced the sst5 selectivity suppressing the sst2 affinity. Finally, a new pharmacophore model for the sst5 was developed.