An Annulation toward Fused Bicyclolactones

Abstract

We have now determined that the mutant designated P86A in this paper is, in actuality, P56A. We attribute this error to a visual mistracking along the DNA sequence, such that primers were constructed to alter the proline at position 56. P56 lies on a surface-exposed loop in the substrate-binding domain, ca. 18 Å away from the bound trifluoroethanol; the corresponding position is either deleted or a proline in the mesophilic and psychrophilic alcohol dehydrogenases, respectively. A comparison of the properties of P86A and P56A will be published at a later date.

The Lewis Acidic Ruthenium‐Complex‐Catalyzed Addition of β‐Diketones to Alcohols and Styrenes Is in Fact Brønsted Acid Catalyzed

“…More recently, the same group has developed a new route to fused lactones, the synthesis of which are based on a cascade addition of b-ketoesters to a cyclic diene followed by an in situ lactonization; the reactions are catalyzed by a combination of Lewis acid and Brønsted acid, GaA C H T U N G T R E N N U N G (OTf) 3 /HOTf. [7] Most of the recent studies of the catalytic addition of b-dicarbonyl compounds to olefins or polyenes are based on palladium, coinage metals, such as silver and gold, and gallium; however, the catalytic activities of other transition metals for this reaction have scarcely been investigated. Reported here is our work on the ruthenium-catalyzed addition of bdiketones to alcohols and styrenes.…”

Reduction of Carbonyl to Methylene: Organosilane-Ga(OTf)3 as an Efficient Reductant System

“…In contrast, we have shown that gallium (III) trifluoromethanesulfonate [Ga(OTf) 3 , gallium triflate], acts as an effective but mild and water tolerant Lewis acid catalyst for many organic synthetic transformations such as Friedel-Crafts alkylations, dehydration of oximes to the corresponding nitriles, Beckman rearrangement, etc. [44][45][46][47][48][49][50][51][52]. We also found that gallium triflate offers the optimum acidity required for ketonic Strecker reaction [53] and the synthesis of various heterocycles such as dihydrobenzimidazolines, benzothiazolines, benzoxazinones etc.…”

Gold-Catalyzed Addition of β-Ketoesters to Alkenes: Influence of Electronic and Steric Effects in the Reaction Outcome

“…However, optimized reaction conditions were accomplished using Bi(OTf) 3 /TfOH as an alternative catalytic system due to the fact that extensive decomposition of starting material was observed using gold catalysts. Some other studies were carried out trying to expand the hydroalkylation of olefins with β-ketoesters mediated by auric cations; however, they were clearly unsuccessful [ 50 ]; furthermore, in some conditions, the gold catalysts exhibited an unusual oxophilic behavior [ 51 ].…”