Synthesis, Biosynthesis, and Absolute Configuration of Vioxanthin

Abstract

Seeing double: The biosynthesis (path a) of the biarylic compound vioxanthin (1) by regio‐ and stereoselective intermolecular oxidative phenol coupling is explored in Penicillium citreoviride and the first enantioselective total synthesis of 1 is described (path b). The absolute configuration of (P,R,R)‐1 and its stereoisomer (M,R,R)‐1 was elucidated by combining synthetic methods and feeding experiments with 13C‐labeled substrates.

Unusual dimeric tetrahydroxanthone derivatives from Aspergillus lentulus and the determination of their axial chiralities

“…The CD Exciton Chirality method has been applied to some axially chiral determinations before, such as those of binaphthyl, biarylic dihydronaphthopyranone3031, and bis(naphtho- γ -pyrone)32. However, a very few exceptions were reported due to their complicated chromophores and non-negligible intense magnetic transition dipole moments3334.…”

Studies on a biomimetic oxidative dimerization approach to the hibarimicins

“…Enzymatic 6 and chemical 7 phenolic oxidative couplings have been described; with chemical methods frequently showing modest to undesired regiocontrol. 8 We started our investigations by examining the oxidative dimerization of electron rich phenol 1 .…”

Naphthopyranones – isolation, bioactivity, biosynthesis and synthesis

“…48 Vioxanthin 26 isolated from the later source was labelled 'Tf-26Vx' and shown to be highly active against Grampositive bacteria (MIC range of 0.045-1.56 mg mL À1 ) and strictly anaerobic Gram-negative bacteria. 51 Application of the exciton chirality method, or comparison of CD spectra to that of vioxanthin 26, has routinely been used to deduce the axial chirality of dimeric naphthopyranones. 38 The CD spectrum of 26 shows a strong positive Cotton effect to longer wavelength and a strong negative one to shorter wavelength that corresponds to 'positive exciton chirality', 50 which in the case of 26 corresponds to a P-conguration at the stereogenic axis according to the Prelog-Helmchen rules.…”