The synthesis and reactivity of nitrile oxides and nitroso carbonyls is well known since a long time, but their use in synthetic applications and in the pharmaceutical field is still quite limited. The aim of this PhD project was to expand the scope of these highly reactive compounds by their application in the synthesis of a small library of isoxazole-based fluorophores and by the use of their reactivity in peptide stapling. For what is concerning the synthesis of nitrile oxide- or nitroso carbonyl-stapled peptides, we explored the synthesis of some unnatural amino acids that could take part in pericyclic reactions. The nitrile oxide stapling required the synthesis of some dipolarophilic amino acids: some alkynyl, alkenyl and nitrile derivatives have been obtained starting from some different natural amino acids. On the other side, for the synthesis of nitrile oxide amino acids, we explored both the formation of oxime and nitro derivatives precursors. The synthesis of a nitroso carbonyl derivative was achieved by the formation of a hydroxamic acid precursor, while as coupling partners for the hetero Diels Alder cycloaddition we attempted the insertion of the cyclopentadienyl moiety on the side chain of some amino acids. The insertion of the obtained amino acids into a peptide sequence was attempted, but the obtained results are still inconclusive. The synthesis of the fluorophores was carried out relying on a fluorescent probe that have been already synthetized by Quadrelli research group. The purpose was in fact the tuning of the optical properties of the fluorophore. We attempted to enhance the fluorescence quantum yield and to shift the absorption and emission wavelengths by the insertion of some different functionalized arylic group on the fluorophore scaffold or by the formation of a more conjugated structure. At the end we obtained a small library of fluorophores with three different structures: two of them are based on an isoxazole core, while the other relies on an enamino ketone boron complex. The optical properties of the fluorescent molecules have been evaluated and the most promising one was inserted in a fluorescent probe for proteasome labelling.
La sintesi e la reattività di nitrilossidi e nitroso carbonili è ben nota in letteratura da molto tempo, ma la loro applicazione sintetica nel campo farmaceutico è ancora abbastanza limitata. Lo scopo di questo progetto di ricerca è stato quello di espandere l’applicazione di questi composti molto reattivi attraverso il loro impiego nella sintesi di una piccola raccolta di fluorofori con struttura isossazolica e mediante l’uso della loro reattività nel campo degli stapled peptides. Per quanto riguarda la sintesi di nitrilossidi- o nitroso carbonili-stapled peptides, abbiamo esplorato la sintesi di alcuni aminoacidi non-naturali che potessero prendere parte a reazioni pericicliche. Lo stapling attraverso nitrilossidi ha richiesto la sintesi di alcuni amino acidi dipolarofili: alcuni derivati alchnilici, alchinilici e nitrilici sono stati ottenuti a partire da diversi amino acidi naturali. D’altra parte, per la sintesi di aminoacidi recanti un gruppo nitrilossido, abbiamo esplorato la sintesi di suoi precursori recanti nitro-gruppi o ossime. La sintesi di un derivato nitroso carbonilico è stata ottenuta attraverso la formazione del realtivo acido idrossamico come precursore, mentre come coupling partner per la cicloaddizione di Diels Alder abbiamo tentato inserire una struttura ciclopentadienilica sulla catena laterale di alcuni amino acidi. Si è dunque tentato l’inserimento degli amino acidi ottenuti in una catena peptidica, ma i risultati sono stati inconcludenti. La sintesi dei composti fluorescenti si è basata su una sonda fluorescente che era già stata sintetizzata dal gruppo di ricerca del prof. Quadrelli. Il nostro scopo era infatti quello di modulare le proprietà ottiche dei fluorofori. Attraverso l’inserimento di alcuni gruppi arilici e la modifica della struttura del fluoroforo abbiamo provato ad aumentarne la resa quantica di fluorescenza e a spostarne lo spettro di assorbimento ed emissione a più basse frequenze. Alla fine è stato ottenuto una piccola raccolta di fluorofori con 3 strutture differenti: due son basate su una struttura isossazolica, mentre la terza si basa su un complesso boro-enaminochetone. Le proprietà ottiche delle molecole sono state misurate e valutate ed il fluoroforo più promettente è stato inserito in una sonda fluorescente per testarne le proprietà in saggi biologici sul proteasoma.
Synthesis of Fluorophores and Stapled Peptides by Pericyclic Reactions
MOIOLA, MATTIA
2021-06-15
Abstract
The synthesis and reactivity of nitrile oxides and nitroso carbonyls is well known since a long time, but their use in synthetic applications and in the pharmaceutical field is still quite limited. The aim of this PhD project was to expand the scope of these highly reactive compounds by their application in the synthesis of a small library of isoxazole-based fluorophores and by the use of their reactivity in peptide stapling. For what is concerning the synthesis of nitrile oxide- or nitroso carbonyl-stapled peptides, we explored the synthesis of some unnatural amino acids that could take part in pericyclic reactions. The nitrile oxide stapling required the synthesis of some dipolarophilic amino acids: some alkynyl, alkenyl and nitrile derivatives have been obtained starting from some different natural amino acids. On the other side, for the synthesis of nitrile oxide amino acids, we explored both the formation of oxime and nitro derivatives precursors. The synthesis of a nitroso carbonyl derivative was achieved by the formation of a hydroxamic acid precursor, while as coupling partners for the hetero Diels Alder cycloaddition we attempted the insertion of the cyclopentadienyl moiety on the side chain of some amino acids. The insertion of the obtained amino acids into a peptide sequence was attempted, but the obtained results are still inconclusive. The synthesis of the fluorophores was carried out relying on a fluorescent probe that have been already synthetized by Quadrelli research group. The purpose was in fact the tuning of the optical properties of the fluorophore. We attempted to enhance the fluorescence quantum yield and to shift the absorption and emission wavelengths by the insertion of some different functionalized arylic group on the fluorophore scaffold or by the formation of a more conjugated structure. At the end we obtained a small library of fluorophores with three different structures: two of them are based on an isoxazole core, while the other relies on an enamino ketone boron complex. The optical properties of the fluorescent molecules have been evaluated and the most promising one was inserted in a fluorescent probe for proteasome labelling.File | Dimensione | Formato | |
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