Synthetic studies on an ABC-ring model of Tubiferal A, a triterpenoid isolated from the fruit bodies of the Tubifera dimorphotheca myxomycete, are described. The stereogenic centers at the angular positions were constructed through the stereoselective addition of a C-ring allylborane followed by an Eschenmoser–Claisen rearrangement reaction prior to the formation of the AB-ring system by a double intramolecular alkylation reaction of a dichloro nitrile intermediate.
<p>H-D exchange at the formyl residue of the natural product malonganenone B was investigated. Models of the system were synthesised and displayed the same exchange. Kinetic studies, performed using NMR spectroscopy, found the exchange was first order with respect to base whilst displaying acid inhibition, in opposition to existing research. Cyclic species, including an N-heterocyclic carbene precursor, were formed that, in conjunction with the previous findings, suggested a carbene-based mechanism was in operation. Further synthetic studies were performed to demonstrate the existence of a carbene. With use of silver oxide, a fulvalene dimer and an organopalladium complex of this carbene were obtained, which provide further support towards a carbene-based mechanism being involved in the H-D exchange of malonganenone B.</p>
<p>H-D exchange at the formyl residue of the natural product malonganenone B was investigated. Models of the system were synthesised and displayed the same exchange. Kinetic studies, performed using NMR spectroscopy, found the exchange was first order with respect to base whilst displaying acid inhibition, in opposition to existing research. Cyclic species, including an N-heterocyclic carbene precursor, were formed that, in conjunction with the previous findings, suggested a carbene-based mechanism was in operation. Further synthetic studies were performed to demonstrate the existence of a carbene. With use of silver oxide, a fulvalene dimer and an organopalladium complex of this carbene were obtained, which provide further support towards a carbene-based mechanism being involved in the H-D exchange of malonganenone B.</p>
Daphniphyllum alkaloids have a complex molecular structure; thus, their synthesis can be challenging. A new method for the construction of the [7-5-5] tricyclic core of Daphniphyllum alkaloids was developed. The bicyclo[5.3.0]decane skeleton was constructed via the divinylcyclopropane rearrangement of a cyclopentenone derivative with a vinylcyclopropyl group at the β-position. After introducing a 2-iodoethyl group via a regioselective Michael addition with phenyl vinyl selenone, the [7-5-5] tricyclic system was formed by the intramolecular alkylation reaction of a cyclopentadienyl anion species.
The bicyclo[2.2.2]diazaoctane alkaloids are a vast group of natural products which have been the focus of attention from the scientific community for several decades. This interest stems from their broad range of biological activities, their diverse biosynthetic origins, and their topologically complex structures, which combined make them enticing targets for chemical synthesis. In this article, full details of our synthetic studies into the chemical feasibility of a proposed network of biosynthetic pathways towards the brevianamide family of bicyclo[2.2.2]diazaoctane alkaloids are disclosed. Insights into issues of reactivity and selectivity in the biosynthesis of these structures have aided the development of a unified biomimetic synthetic strategy, which has resulted in the total synthesis of all known bicyclo[2.2.2]diazaoctane brevianamides and the anticipation of an as-yet-undiscovered congener.
Synthetic studies towards isomeric pyrazolopyrimidines as potential ATP synthesis inhibitors of Mycobacterium tuberculosis. Structural correction of reported N-(6-(2-(dimethylamino)ethoxy)-5-fluoropyridin-3-yl)-2-(4-fluorophenyl)-5-(trifluoromethyl)pyrazolo[1,5-α]pyrimidin-7-amine
