The synthesis and evaluation of chiral phosphines 11, 15a, 19a, 24a, and 28a as nucleophilic catalysts for anhydride activation and kinetic resolution of alcohols is described. The relative reactivity follows the order 11a > 11b > 15a > 1 in the monocyclic series, and 24a > 19a > 28ain the bicyclic series, with an overall rate advantage of ca. 2 orders of magnitude for the bicyclic phospholanes over the monocyclic analogues. The increased reactivity of the bicyclic phospholanes for the acylation of alcohols is attributed to conformational effects and ground-state destabilization in a highly associative mechanism. Kinetic resolution data demonstrate promising enantioselectivities for 24a.

The development of new RNA‐binding ligands is attracting increasing interest in fundamental science and the pharmaceutical industry. The goal of this study was to improve the RNA binding properties of triplex‐forming peptide nucleic acids (PNAs) by further increasing the pKa of 2‐aminopyridine (M). Protonation of M was the key for enabling triplex formation at physiological pH in earlier studies. Substitution on M by an electron‐donating 4‐methoxy substituent resulted in slight destabilization of the PNA–dsRNA triplex, contrary to the expected stabilization due to more favorable protonation. To explain this unexpected result, the first NMR structural studies were performed on an M‐modified PNA–dsRNA triplex which, combined with computational modeling identified unfavorable steric and electrostatic repulsion between the 4‐methoxy group of M and the oxygen of the carbonyl group connecting the adjacent nucleobase to PNA backbone. The structural studies also provided insights into hydrogen‐bonding interactions that might be responsible for the high affinity and unusual RNA‐binding preference of PNAs.

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An efficient, convergent synthesis of the core bicyclo[4.3.1]decane ring system of welwitindolinones is described. Key steps in the synthesis include an intramolecular palladium-catalyzed enolate arylation reaction to create the desired bicyclic skeleton and a Curtius rearrangement to install the bridgehead isocyanate unit. [reaction: see text]