Total Synthesis of Aurofusarin: Studies on the Atropisomeric Stability of Bis‐Naphthoquinones

Abstract

An efficient annulation involving pyrone addition to a quinone and Dieckmann condensation was developed for rapid assembly of a γ-naphthopyrone monomeric precursor to the bis-naphthoquinone natural product aurofusarin. Dimerization was achieved through Pd -catalyzed dehydrogenative coupling. Further studies employing asymmetric nucleophilic epoxidation indicate that the atropisomers of aurofusarin and derivatives are not configurationally stable at ambient temperature.

Asymmetric Synthesis of Gonytolide A: Strategic Use of an Aryl Halide Blocking Group for Oxidative Coupling

“…In addition, no interconversion of 1 and 16 was observed after thermolysis of either compound in refluxing toluene for 24 h. The rotational barrier for interconversion of atropisomers was calculated to be 47.5 kcal/mol using the B3LYP/6-31G(d) level of theory. 5 Although the rotational barrier is high, the Pappo group 11a and others 39 have demonstrated that BINOL can undergo racemization under oxidative conditions. This prompted us to examine single electron transfer (SET) conditions with either atrop -gonytolide A ( 16 ) or its brominated precursor bromo- atrop -gonytolide A ( 27 ) (Table 3).…”

Diversity in Fungal Intermolecular Phenol Coupling of Polyketides: Regioselective Laccase‐Based Systems

“…If any one of the four involved enzymes were knocked out, no dimer formation was observed . The stereoselectivity of the coupling reaction is difficult to determine because aurofusarin does not form stable atropisomers due to its quinone moieties …”

Stereoselective Synthesis of Optically Pure 2-Amino-2′-hydroxy-1,1′-binaphthyls

“…The basic factors that determine the observed stereoselectivity were investigated. Rotation around the biaryl bond, a consequence of BINOL-to-metal charge transfer, results in a rapid loss of optical purity in 3,3′-unsubstituted BINOLs. ,,, Similarly, ( R a )-NOBIN- 2 underwent complete racemization within 5 h in the presence of FeCl 3 (10 mol %, Figure A, black circles); this phenomenon was utilized by Kočovsky for the kinetic resolution of 2 by a stoichiometric amount of chiral copper amine complexes . Furthermore, a rapid atropoisomerization process took place when NOBINs 6a and 7a were treated in two separate vials under the reaction conditions, leading to the formation of thermodynamic mixtures with similar diatereoisomeric ratios ( 6a : 7a , 1.5:1, Figure B, red and blue circles).…”