Nuovi motivi azabiciclo [X.2.1] alcanici

Abbiamo intrapreso uno studio accurato avente come oggetto la reazione tra un reagente silossidienico a base pirrolica il N-(terzbutilossicarbonil)- 2-(terz-butildimetilsililossi)pirrolo (TBSOP, 1), e una serie di accettori chetonici di varia natura, simmetrici ed asimmetrici, enolizzabili e non, achirali prochirali e chirali prochirali enantiopur

Sintesi totale di amminoacidi a base ciclitolica: un approccio orientato alla diversità

Amminoacidi carbociclici con funzionalità multiple installate sulle varie posizioni anulari, come le strutture polioliche 1-8 di questo studio, rappresentano un insieme molecolare omogeneo e, allo stesso tempo, variato, in cui ciascuna entità può essere vista sotto diverse angolazioni

Sintesi di nuove strutture macrocicliche a ridotta libertà conformazionale

L'obiettivo della nostra ricerca consiste nella creazione di nuove strutture macrocicliche a ridotta libertà conformazionale che incorporino la sequenza consensus RGD per mezzo di una funzione γ-amminoacidica supportata da anelli ciclopentanici (Acpca), ossidrilati e non. Tali scaffold amminoacidici possono essere visti di fatto come mimetici dell’acido γ- amminobutanoico bloccato in una conformazione a W da un ponte α,γ-etilene o idrossietilene. La valutazione biologica in vitro dei ciclo-pseudopeptidi mediante test di binding verso i recettori αvβ3 e αvβ5 isolati, l’approfondito studio strutturale in soluzione via NMR e, infine, studi di docking eseguiti sulla struttura a raggi X del segmento extracellulare dell’integrina αvβ3 complessata con il composto di riferimento EMD121974 hanno completato il nostro studio

Direct-type vinylogous Mukaiyama-Michael addition reactions involving pyrrolinone donors

The direct Mukaiyama-Michael addition of vinylogous tetramate donors to a number of different Michael acceptors has been easily executed, by employing the TMSOTf/Et3N mixture as soft Lewis acid/base promoter agent. Richly functionalized, highly manipulable y-substituted pyrrolinone products were practically synthesized in acceptable to excellent yields, and with diastereoselectivities heavily relying upon the substituent at the nitrogen atom of the pyrrolinone donor

Further uses of pyrrole-based dienoxysilane synthons: a full aldol approach to azabicyclo[x.2.1]alkane systems

Two racemic 2-azabicyclo[2.2.1]heptane structures, 15 and 21, and two chiral non-racemic 6-azabicyclo[3.2.1]octane representatives, 28 and 36, have been synthesized starting from 1-(tert-butoxycarbonyl)-2-(tert-butyldimethylsilyloxy)pyrrole (TBSOP, 5) and suitable ketones, 9, 16, 22 and 29. 2-Azabicycle 15 was then elaborated to racemic cyclopentane amino acid 38, while 6-azabicycle 36 served to access the enantiomerically pure normorphan-type structure 40. For all substrates, a uniform synthetic scheme was implemented based on the combination of two diastereoselective aldol-type carbon-carbon bond-forming reactions, the efficiencies of which were secured by appropriate aldol-stabilizing steps. A mechanistic rationale accounting for the markedly diastereoselective character of the key Mukaiyama aldol reactions between TBSOP and the ketone acceptors has been postulated that involves hetero-Diels-Alder transition-state structures in which the preference for endo versus exo addition is governed by the electronic nature of the substituents in the ketone substrates

Synthesis and preclinical evaluation of a novel, selective 111-In-labelled aminoproline-RGD-peptide for non-invasive melanoma tumor imaging

In recent years, many efforts have been addressed to the development of new imaging techniques enabling early diagnosis and non-invasive monitoring of primary tumors and metastases. Among the integrin family, αVβ3 and α5β1 receptors have been characterized as prototypic markers of angiogenic tumor-associated endothelial cells and their overexpression in tumor cells has been correlated with the progression of various tumor types such as melanoma. Herein, we report the synthesis, characterization and preclinical evaluation of an 111-In-labelled DOTA conjugate embodying a cyclic aminoproline-RGDpeptide motif as a competent αVβ3 integrin ligand, to be used as a radiotracer in preclinical models of human melanoma. Practical and efficient chemical and radiochemical synthetic procedures were set up, the in vitro stability and hydrophilicity of a cold c(AmpRGD)-DOTA conjugate were demonstrated, the binding affinities toward isolated αVβ3/α5β1 receptors were assayed and inhibition of cell adhesion to vitronectin and fibronectin was tested in human melanoma and endothelial progenitor cell lines. The anti-angiogenic activity of the peptide conjugates was also tested and assessed in vitro by tubulogenesis assays. The in vivo biodistribution SPECT/CT studies in healthy mice revealed high renal uptake at earlier observation times (30 min to 4 h p.i.) and complete clearance from the kidney at 48 h p.i.; the displacement experiments in human melanoma xenografts confirmed the αVβ3/α5β1 integrin specificity of tumor uptake, suggesting the 111-In-labelled c(AmpRGD)-DOTA bioconjugate as a promising starting point in the search for new SPECTimaging small-molecular probes for non-invasive visualization of tumor angiogenesis, human melanoma and other αVβ3/α5β1-positive tumors

Design, Synthesis, and Biological Evaluation of Novel cRGD–Paclitaxel Conjugates for Integrin-Assisted Drug Delivery

The efficacy of taxane-based antitumor therapy is limited by several drawbacks which result in a poor therapeutic index. Thus, the development of approaches that favor selective delivery of taxane drugs (e.g., paclitaxel, PTX) to the disease area represents a truly challenging goal. On the basis of the strategic role of integrins in tumor cell survival and tumor progression, as well as on integrin expression in tumors, novel molecular conjugates were prepared where PTX is covalently attached to either cyclic AbaRGD (Azabicycloalkane-RGD) or AmproRGD (Aminoproline-RGD) integrin-recognizing matrices via structurally diverse connections. Receptor-binding assays indicated satisfactory-to-excellent α_Vβ₃ binding capabilities for most conjugates, while <i>in vitro</i> growth inhibition assays on a panel of human tumor cell lines revealed outstanding cell sensitivity values. Among the nine conjugate ensemble, derivative <b>21</b>, bearing a robust triazole ring connected to ethylene glycol units by an amide function and showing excellent cell sensitivity properties, was selected for <i>in vivo</i> studies in an ovarian carcinoma model xenografted in immunodeficient mice. Remarkable antitumor activity was attained, superior to that of PTX itself, which was associated with a marked induction of aberrant mitoses, consistent with the mechanism of action of spindle poisons. Overall, the novel cRGD-PTX conjugates disclosed here represent promising candidates for further advancement in the domain of targeted antitumor therapy