1,721,052 research outputs found
4-[(4’-Methylphenyl)sulfonyl]-1-(triphenylphosphoranylidene)-2-butanone: a new versatile building block for substituted divinyl ketones in the synthesis of natural products
No full textReactivity and synthetic applications of a new synthon for substituted divinyl ketones, namely 4-[(4’-methylphenyl)sulfonyl]-1-(triphenylphosphoranylidene)-2-butanone, are reviewed. The title compound has been conveniently used in “tandem” reactions allowing for the construction of six-membered hetero- and carbocyclic rings, either in homogeneous-phase or solid-phase. Moreover, generation of its alpha-sulfonyl anion offered an easy access to multifunctionalized linear carbon frameworks. The compounds obtained through the use of 4-[(4’-methylphenyl)sulfonyl]-1-(triphenylphosphoranylidene)-2-butanone represented convenient precursors for the synthesis of several natural products, such as (±)-epibatidine, (-)-anabasine, (±)-pyrenophorin and carbacephams
Ethyl 5-[(4-Methylphenyl)sulfonyl]-3-oxopentanoate
No full textEthyl 5-[(4-methylphenyl)sulfonyl]-3-oxopentanoate proves to act as a synthetic equivalent of Nazarov’s reagent, which can be generated in situ under basic conditions and used in annulation reactions leading to functionalized mono- and bicyclic carbocycles
Experimental design methodology applied to optimize a microwave assisted synthesis of the fragrant compound Calone 1951® (comunicazione orale)
No full textHagemann's ester: a timeless building block for natural product synthesis
No full textThe potential of Hagemann’s ester as a building block in the synthesis of complex and biologically active natural products is the topic of this report. Hagemann’s ester chemical transformations allowed the development of diverse and creative applications frequently entailing a wide range of new and modern chemistry. The collected material, covering the development of its chemistry from the very beginning up to the present time, has been organized in sections where the papers listed are discussed in chronological order. Sections 1 and 2 are dedicated to a short introduction and to a description of the different preparations of Hagemann’s ester. The alkylation of the vinylogous beta-keto ester system, the most common operation on the starting ester, has been discussed in detail in Section 3. Synthetic applications involving chemical modifications of the ester functionality, namely removal, preservation and elaboration, have been considered in Sections 4–6, while syntheses featuring Hagemann’s ester fragmentation into linear carbon chains are collected in Section 7. Finally, Section 8 has been dedicated to the preparation and synthetic applications of optically active Hagemann’s ester derivatives. For the sake of clarity, the carbon-atom fragments of the different synthetic targets coming from Hagemann’s ester or its analogues are marked in red
O-Silyl triflate-promoted addition of diethyl phosphite to chiral aldonitrones. A rapid access to complex alpha-amino phosphonates and their N-hydroxy derivatives
No full textThe addition reaction of diethyl phosphite to O-silylated N-benzyl nitrones derived from chiral alpha-alkoxy and N-Boc
alpha-amino aldehydes has been studied as a stereoselective carbon-phosphorus bond forming process for the synthesis of
polyhydroxylated alpha-amino and alpha,beta-diamino phosphonates. Key intermediates are the corresponding N-hydroxy alpha-amino phosphonates
Sintesi di (±)-2-azetidinoni da beta-enamminochetoesteri
No full textIl nucleo 2-azetidinonico (beta-lattamico) rappresenta l'unità strutturale comune ad un gran numero di composti biologicamente attivi, tra cui penicilline e cefalosporine. L'importanza farmacologica degli antibiotici beta-lattamici e la crescente richiesta di farmaci aventi una più elevata stabilità chimica e metabolica rendono ancora particolarmente attraente lo sviluppo di nuove metodologie per l'ottenimento del nucleo beta-lattamico in maniera semplice e stereoselettiva.
Il nostro contributo in questo campo si è concretizzato nella sintesi diastereoselettiva di 3-(1-idrossietil)-2-azetidinoni protetti, strutturalmente correlati alla tienamicina, in forma racemica. Il passaggio chiave è rappresentato dalla reazione di ciclizzazione di opportuni beta-ammino esteri che si ottengono per elaborazione di beta-enamminochetoesteri, facilmente ottenuti per reazione del metil acetoacetato con alchil cianoformiati in presenza di quantità catalitiche di [Zn(acac)2
Tert-butil (R)-3-idrossi-4-pentenoato, un conveniente ¿building block¿ chirale per la sintesi di sostanze naturali
No full textLe interessanti proprietà biologiche di composti naturali a struttura aza-eterociclica rende ancora particolarmente attraente lo sviluppo di nuove metodologie sintetiche per l’ottenimento di nuclei azotati in maniera semplice e stereoselettiva.
Il nostro interesse in questo campo si è concretizzato nella sintesi enantioselettiva di (1S,5S,6R)-6-idrossi-tropinone e nella sintesi enantiodivergente del lattone di Geissman-Waiss, precursore di alcaloidi pirrolizidinici, utilizzando, come materiale di partenza, (R)-tert-butil-3-idrossi-4-pentenoato.
Intermedi chiave sono rappresentati da metil (R)-6-(tert-butossicarbonilammino)ossi-4-idrossi-2-esenoato e dalla malicaldeide tetrametilacetale, facilmente ottenibili, in forma enantiomericamente pura, da (R)-tert-butil-3-idrossi-4-pentenoato attraverso reazioni classiche della chimica organica
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