In the last decades, studies on Titanium derivatives have focused mainly on the replacement of cyclopentadienyl rings with various ligands, finding an excellent method of modulating their chemical and physical properties. We wanted to direct here our research, paying attention to the functionalization of these compounds through bio-orthogonal reactions. Bio-orthogonal chemistry consists of a series of reactions that can take place within biological systems without interfering with their normal functioning: selectivity, efficiency and compatibility with the aqueous environment are, therefore, the three peculiar characteristics of this field of research. Until now, the patented bioorthogonal reactions are of different types, but, in particular, we will focus on the study of two of these: the click-chemistry reaction Strain Promoted [3 + 2] Azide-Alkyne Cycloadditions (SPAAC) and Tetrazine Ligation, which fall under the Diers-Alder (iEDDA) inverse-electron demand reactions. The SPAACs were performed without the aid of a metal catalyst - such as Copper (I) - activating the Titanocene with a highly tensioned cyclic alkyne: this is a linker placed on the upper Cp ring elaborated by our research group some years ago. This functionality has shown an excellent affinity in the binding with tetrazines and variously substituted azides. Another type of linker used, especially related to tetrazines, exploits the reactivity of norbornene. The aim of the present study was therefore to synthesize appropriate linkers in order to activate these Titanium coordination complexes to promote bio-orthogonal reactions. Thus, the Titanocene obtained were subsequently conjugated to tetrazine and to different biomolecules - alendronic acid, folic acid and biotin - with the aim of increasing target selectivity in antitumoral chemotherapy. The most relevant results have been obtained in the conjugation with folic acid, whose chemical-physical and biological characteristics have been studied in the present work. Reactions with alendronic acid and biotin have provided less appreciable results and will be subject to further optimization in the future.
Negli ultimi due decenni, gli studi sui derivati del Titanio si sono focalizzati prevalentemente sulla sostituzione degli anelli ciclopentadienilici con svariati leganti, trovando un ottimo metodo di modulazione delle loro proprietà chimico-fisiche. È qui che abbiamo voluto indirizzare la nostra ricerca, ponendo particolare attenzione sulla funzionalizzazione di tali composti tramite reazioni bioortogonali. La chimica bioortogonale racchiude una serie di reazioni che possono avvenire allinterno di sistemi biologici senza interferirne con il loro normale funzionamento: selettività, efficienza e compatibilità con lambiente acquoso sono, dunque, le tre caratteristiche peculiari di questo settore di ricerca. Sino ad ora, le reazioni bioortogonali brevettate sono di diverse tipologie, ma, in particolare, approfondiremo lo studio di due di queste: la reazione di click-chemistry del tipo Strain Promoted [3 + 2] Azide-Alkyne Cycloadditions (SPAAC) e di Tetrazine Ligation, che rientrano nelle reazioni di inverse-electron demand Diels-Alder (iEDDA). Le SPAAC sono state eseguite senza lausilio di un catalizzatore metallico - come ad esempio il Rame(I) - attivando il Titanocene con un alchino ciclico altamente tensionato: si tratta un linker situato su uno dei due anelli Cp elaborato dal nostro gruppo di ricerca alcuni anni fa. Questa funzionalità si è dimostrata estremamente affine al legame con tetrazine ed azidi variamente sostituite. Un altro tipo di linker utilizzato, affine in special modo alle tetrazine, sfrutta la reattività del norbornene. La finalità del presente studio, dunque, è stata quella di sintetizzare opportuni linkers in modo da attivare questi complessi di coordinazione al Titanio nei confronti di reazioni bioortogonali. I Titanoceni così ottenuti sono stati successivamente coniugati a tetrazine e a diverse biomolecole - acido alendronico, acido folico e biotina - con lo scopo di aumentarne la selettività di bersaglio in vista di un impiego in chemioterapia antitumorale. I risultati più rilevanti sono stati ottenuti nella coniugazione con lacido folico, le cui caratteristiche chimico-fisiche e biologiche sono state approfondite nel presente studio. Le reazioni con acido alendronico e biotina hanno fornito risultati meno apprezzabili e saranno oggetto di ulteriori ottimizzazioni in futuro.
Sintesi e caratterizzazione di linkers impiegati nella funzionalizzazione di Titanoceni tramite reazioni bioortogonali
SALOMONI, VITTORIA
2018/2019
Abstract
In the last decades, studies on Titanium derivatives have focused mainly on the replacement of cyclopentadienyl rings with various ligands, finding an excellent method of modulating their chemical and physical properties. We wanted to direct here our research, paying attention to the functionalization of these compounds through bio-orthogonal reactions. Bio-orthogonal chemistry consists of a series of reactions that can take place within biological systems without interfering with their normal functioning: selectivity, efficiency and compatibility with the aqueous environment are, therefore, the three peculiar characteristics of this field of research. Until now, the patented bioorthogonal reactions are of different types, but, in particular, we will focus on the study of two of these: the click-chemistry reaction Strain Promoted [3 + 2] Azide-Alkyne Cycloadditions (SPAAC) and Tetrazine Ligation, which fall under the Diers-Alder (iEDDA) inverse-electron demand reactions. The SPAACs were performed without the aid of a metal catalyst - such as Copper (I) - activating the Titanocene with a highly tensioned cyclic alkyne: this is a linker placed on the upper Cp ring elaborated by our research group some years ago. This functionality has shown an excellent affinity in the binding with tetrazines and variously substituted azides. Another type of linker used, especially related to tetrazines, exploits the reactivity of norbornene. The aim of the present study was therefore to synthesize appropriate linkers in order to activate these Titanium coordination complexes to promote bio-orthogonal reactions. Thus, the Titanocene obtained were subsequently conjugated to tetrazine and to different biomolecules - alendronic acid, folic acid and biotin - with the aim of increasing target selectivity in antitumoral chemotherapy. The most relevant results have been obtained in the conjugation with folic acid, whose chemical-physical and biological characteristics have been studied in the present work. Reactions with alendronic acid and biotin have provided less appreciable results and will be subject to further optimization in the future.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/22048