Carolyn A. Leverett

Synthesis of 2,4-disubstituted pyrroles by rearrangements of 2-furanyl carbamates.

2,4-Disubstituted pyrroles were synthesized by an oxidative rearrangement of a furanyl carbamate followed by sequential reaction of the resulting 5-methoxypyrrol-2(5H)-one with different alkyl lithiates. The final step of the procedure involves heating the ring opened 1-methoxy-5-oxopentylcarbamate with a primary amine.

Switching between Concerted and Stepwise Mechanisms for Dyotropic Rearrangements of β-Lactones Leading to Spirocyclic, Bridged γ-Butyrolactones

Quantum chemical computations (B3LYP/6-31+G(d,p)) were applied to examine the mechanisms of dyotropic rearrangements of spirolactones in order to assess whether these reactions are concerted. Mechanistic experiments, designed on the basis of the results of these calculations, support the conclusions derived from theory. In particular, Zn(II) salts or Brønsted acids induce stepwise dyotropic processes, whereas dyotropic rearrangements mediated by silyltriflates are concerted processes. Additional products isolated with Zn(II) salts support a stepwise process with a carbocationic intermediate. Furthermore, a facile Grob-type fragmentation emanating from both a tricyclic-β-lactone and a spiro-γ-lactone was identified.

Cycloaddition across the benzofuran ring as an approach to the morphine alkaloids.

The intramolecular Diels-Alder reaction of several amidofurans tethered onto a benzofuran ring was examined as a strategy for the synthesis of morphine. Bromo substitution on the furan ring did not provide sufficient activation to allow the cycloaddition to take place across the aromatic benzofuran. However, the presence of a large o-methylbenzyl group on the amido nitrogen atom causes the reactive s-trans conformation of the amidofuran to be highly populated, thereby facilitating its Diels-Alder cycloaddition across a tethered benzofuran.

Synthetic Approaches to the New Drugs Approved During 2015

New drugs introduced to the market every year represent privileged structures for particular biological targets. These new chemical entities (NCEs) provide insight into molecular recognition while serving as leads for designing future new drugs. This annual review describes the most likely process-scale synthetic approaches to 29 new chemical entities (NCEs) that were approved for the first time in 2015.