Gotowa bibliografia na temat „Tridachiapyrone”

Organom etallic π-complexes are defined as the synthetic equivalents of cationic synthons for use in organic synthesis. W hen complexes of this type are employed, activation and stereocontrol effects (which arise from properties of the metal), and regiocontrol effects and functional group locations (resulting from substitution pattern), are separated from one another. The consequences of this distinction for synthesis design are discussed by using two examples, an approach for the synthesis of tridachiapyrones based on a ‘linear’ synthetic sequence, and an alternative method for double alkylations employing an ‘iterative’ strategy. Access to resolved compounds for enantiom er synthesis is described.

Une étude synthétique combinée à des travaux en méthodologie ont été développés, incluant : - La synthèse de la tridachiapyrone B, produit naturel de la famille des polypropionates à motif α’-méthoxy-γ-pyronepyrone, avec une stratégie basée sur deux étapes de désymétrisation clés dont une réalisée avec une diènone prochirale. - Une étude méthodologique menée sur les complexes ate de l’étain démontrant pour la première fois la réactivité et la sélectivité de ces espèces pour transférer des groupements allyles substitués sur des électrophiles peu réactifs tels que cétones et énones - Une étude méthodologique de la réaction de Mannich organocatalysée appliquée à des aldéhydes encombrés et chiraux afin d’atteindre le coeur de la lyconadine A et des composés spirocycles
Three studies combining natural product synthesis and methodologies were carried out, including: - Synthetic studies toward tridachiapyrone B, a polypropionate containing α-méthoxy-γ-pyrone ring, were developed, the strategy involving two desymmetrization steps, one of them being with a prochiral dienone. - A methodology demonstrating for the first time the reactivity and selectivity of tin ate complexes has been designed for the allylation reactions of ketones and enones, as unreactive electrophiles. - Organocatalytic Mannich reactions have been investigated and applied to hindered and chiral aldehydes for the construction of the core of lyconadin A and various spirocyclic systems

Since the middle of the 20th century, significant interest has evolved from the scientific community towards the polypropionate family of marine natural products. A number of these compounds have been shown to possess significant biological activity, and this property, as well as their structural complexity, has driven numerous efforts towards their synthesis. The first chapter provides an introduction into the world of polypropionates, with a discussion on synthetic studies into a number of members of the tridachiapyrone family. Fundamental synthetic concepts utilised in this thesis towards the preparation of polyketides are also described, with a focus on their application towards the synthesis of 9,10-deoxytridachione, anti tridachiahydropyrone and syn tridachiahydropyrone. Chapter 2 describes the work undertaken towards the total synthesis of 9,10-deoxytridachione. The novel tandem conjugate addition-Dieckmann condensation of complex enones developed previously in the Perkins group was used to generate anti methylated cyclohexenones as key synthetic intermediates. The conversion of the cyclohexenones into the corresponding cyclohexadienes via allylic alcohols was attempted, utilising a Grignard-mediated reaction to achieve the selective 1,2-reduction. Studies into the Grignard-mediated reduction were also undertaken on seven additional cyclohexenones, in order to investigate the utility and scope of the reaction. The extension of the methodology previously developed for the synthesis of cyclohexenones is the subject of Chapter 3. This section describes investigations into the synthesis of stereochemically-diverse cyclohexenones from complex enones. The conjugate addition-Dieckmann condensation strategy was extended successfully towards the synthesis of a syn methylated cyclohexenone, which allowed the synthesis of the proposed true structure of tridachiahydropyrone to be pursued. The methodology developed in Chapter 3 was utilised in Chapter 4 to synthesise a model system of syn tridachiahydropyrone. A comparative analysis of the NMR data of the syn model, an anti model and anti tridachiahydropyrone with the natural product indicated that the true structure of tridachiahydropyrone may indeed have syn stereochemistry. The synthesis of syn tridachiahydropyrone was attempted, and to this end a suitable cyclohexanone was successfully synthesised. However, the subsequent methylation-elimination cascade failed to furnish the desired syn methylated cyclohexenone, producing only an anti methylated cyclohexanone. The stereochemistry of the methylation was deduced using high and low variable temperature NMR coupled with selective irradiation NOESY.