One-Pot Access to Functionalised Malamides via Organocatalytic Enantioselective Formation of Spirocyclic β-Lactone-Oxindoles and Double Ring-Opening

Malamides (diamide derivatives of malic acid) are prevalent in nature and of significant biological interest, yet only limited synthetic methods to access functionalised enantiopure derivatives have been established to date. Herein, an effective synthetic method to generate this molecular class is developed through in situ formation of spirocyclic β-lactone-oxindoles (employing a known enantioselective isothiourea-catalysed formal [2+2] cycloaddition of C(1)-ammonium enolates and isatin derivatives) followed by a subsequent dual ring-opening protocol (of the β-lactone and oxindole) with amine nucleophiles. The application of this protocol is demonstrated across twelve examples to give densely functionalised malamide derivatives with high enantio- and diastereo-selectivity (up to >95:5 dr and >99:1 er).

Convenient synthesis of N-alkyl-3,1-benzoxazin-2-ones from carbamate protected anthranil aldehydes and ketones via one-step alkylation/alkoxy rearrangement

A practical and step-economical protocol was developed to prepare N-alkyl-3,1-benzoxazin-2-one derivatives from anthranil aldehydes and ketones via one-step alkylation/alkoxy rearrangement, where three new chemical bonds and one ring were constructed in a single step. Control studies revealed a stepwise mechanism and that the alkoxy rearrangement was an intermolecular process.

Electrochemical Rearrangement of 3-Hydroxyoxindoles into Benzoxazinones

We report an unexpected rearrangement of 3-hydroxyoxindoles into benzoxazinones using electrochemistry. Our reaction employs mild and environmentally friendly conditions, and the benzoxazinone products are obtained in moderate to excellent yields. Mechanistic experiments suggest that a peroxide intermediate is likely involved.

Crystal structure of isopropyl 2-hy-droxy-2-phenyl-acetate: a pharmacopoeia reference standard

The title compound, C11H14O3, is used as a pharmacopoeia reference standard for determining impurities in the drug Pregabalin, used for the treatment of epilepsy and diabetic neuropathic pain. The mol-ecule is far from being planar, with the dihedral angle between the planes of the aromatic ring and the carboxyl fragment (O-C=O) being 76.1 (6)°. The isopropyl substituent is located in a synperiplanar position relative to the C=O bond and is turned so that the C-O-C-H torsion angle is -43.7°. In the crystal, bifurcated O-H⋯(O,O) hydrogen bonds, enclosing R12(5) ring motifs, lead to the formation of chains propagating along the c-axis direction. Inversion-related chains are linked by the C-H⋯O hydrogen bonds, forming undulating layers lying parallel to the bc plane.

Preparation of O-Methyl Substituted 2-Oxofuro- and 2-Oxopyrrolidinoindolines by Reductive Lactonization of Oxindol-3-Ylacetic Acids

A practical procedure for the preparation of O-methyl substituted 3a,8-dialkyl-2-oxofuroindolines is described. Reductive lactonization of the corresponding oxindol-3-ylacetic acids provides a route for the formation of this class of compounds. Further transformation of 2-oxofuroindolines into 2-oxopyrrolidinoindolines, and then to pyrrolidinoindolines demonstrates their versatility as key intermediates in natural products synthesis. The results of single-crystal X-ray crystallographic analyses are given for five of the studied compounds.