Establishment of atropisomerism in 3-indolyl furanoids: a synthetic, experimental and theoretical perspective

A number of axially chiral 3-indolyl furanoids have been synthesized and the individual enantiomers are found to be configurationally stable and isolable at room temperature.

Dynamic kinetic resolution of biaryl atropisomers by chiral dialkylaminopyridine catalysts

Dynamic kinetic resolutions of atropisomers using chiral DMAPs with fluxional chirality.

Alkynylation of heterocyclic compounds using hypervalent iodine reagent

The alkynylation of various nitrogen- and/or sulphur-containing heterocyclic compounds using hypervalent iodine TMS-EBX by utilization of tertiary amines under mild conditions is described. The developed metal-free methodology furnishes the corresponding alkynylated heterocycles bearing quaternary carbon in high yields.

Enantioselective total synthesis and studies into the configurational stability of bismurrayaquinone A

Lost in rotation: the concise strategy of the first enantioselective total synthesis of bismurrayaquinone A utilized traceless stereochemical exchange to form an enantioenriched biphenyl core that was elaborated in a bidirectional manner to the natural product. Observed racemization on an unsuccessful initial route prompted studies into the configurational stability of bismurrayaquinone A and related biquinones.

Biarylic biscarbazole alkaloids: occurrence, stereochemistry, synthesis, and bioactivity

The structurally and pharmacologically intriguing but stereochemically initially disregarded small class of biarylic biscarbazole alkaloids is presented, starting with an introduction of the different structural patterns found in nature. For the construction of the biaryl bond, mainly biomimetic oxidative coupling reactions were used, as shown for the natural products bismurrayaquinone-A, bis-2-hydroxy-3-methylcarbazole, clausenamine-A, and murrastifoline-F. For most of these compounds, a resolution of the respective atropo-enantiomers succeeded either directly, by high-performance liquid chromatography by HPLC on a chiral phase, or via atropo-diastereomers, after derivatization with a chiral auxiliary. The absolute configurations of the pure enantiomers were assigned by comparison of experimental (CD) spectra with those quantum chemi-cally calculated, or, for atropo-diastereomeric derivatives, by means of ROESY investigations and X-ray crystallography. Ullmann-type coupling conditions were also found to be feasible for the construction of the 2,2'-biscarbazole core, necessitating a completely regioselective 2-bromination protocol. The first atroposelective synthesis of such a basic target structure was achieved by application of the "lactone methodology," giving rise to an atropisomeric ratio of 85 : 15. Some of the biscarbazole alkaloids and their derivatives were found to have interesting bioactivities, and for the first time, the natural atropo-enantiomeric ratio in the plants was determined for one of these compounds, murrastifoline-F.