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Brønsted acids, such as phosphoric acids derived from chiral 1,1′‐bi‐2‐naphthol (BINOL), are important catalysts in the formation of carbon–carbon and carbon–heteroatom bonds, for example. The catalytic activity of these Brønsted acids is strongly linked to their acidity, and as such, the evaluation of compounds to determine pKa values provides insight into their catalytic activity. Herein, a 19F{1H} NMR methodology is detailed to determine the pKa of a fluorinated binaphthyl‐derived phosphinic acid, rac‐1, in acetonitrile and in the presence of a fluorinated sulfonamide reference compound (2–4). The approach was tested initially using 2 and 3, with the ΔpKa (0.08) in strong agreement with previously reported values (6.6 for 2 and 6.68/6.73 for 3). Sigmoidal curves of normalised chemical shift change (Δδ) against equivalents of the base phosphazene P1‐tBu added overlapped for 2 and 3, but in the case of rac‐1 and either 2, 3 or 4, there was significant separation. A variety of different approaches for determining the ΔpKa were compared. Values of pKa determined when the normalised Δδ was 90% were optimal for 2 and 3, whereas a normalised Δδ of 75% was optimal for 4, resulting in the pKa of rac‐1 being determined to be 8.47–8.71. [ABSTRACT FROM AUTHOR]

An ω‐transaminase‐triggered intramolecular aza‐Michael reaction has been employed for the preparation of cyclic β‐enaminones in good yield and excellent enantio‐ and diastereoselectivity, starting from easily accessible prochiral ketoynones and commercially available enzymes. The powerful thermodynamic driving force associated with the spontaneous aza‐Michael reaction effectively displaces the transaminase reaction equilibrium towards product formation, using only two equivalents of isopropylamine. To demonstrate the potential of this methodology, this biocatalytic aza‐Michael step was combined with annulation chemistry, affording unique stereo‐defined fused alkaloid architectures. [ABSTRACT FROM AUTHOR]

An alcohol dehydrogenase‐mediated asymmetric reduction and subsequent intramolecular oxa‐Michael reaction has been developed for the preparation of tetrahydropyrans (or oxanes) and tetrahydrofurans, in excellent conversion, yield and high enantiomeric and diastereomeric excess. To highlight the utility of the methodology, we report the synthesis of an analogue of the fungal antioxidant brocaketone A. Also described is the preparation of the (–)‐(R,R)‐enantiomer of the natural product, (+)‐(S,S)‐(cis‐6‐methyltetrahydropyran‐2‐yl)acetic acid. [ABSTRACT FROM AUTHOR]