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.

The chemoenzymatic synthesis of the tert-butyl (S)-6-chloro-5-hydroxy-3-ketohexanoate is described. Our approach relies on a highly regio- and enantioselective reduction of a beta,delta-diketohexanoate ester catalysed by NADP(H)-dependent alcohol dehydrogenase of Lactobacillus brevis (LBADH). A detailed description of the scale-up of the enzymatic synthesis of the hydroxyketo ester is given which includes a scale-up of the substrate synthesis as well, i.e. the preparation of diketo ester on a 100 g scale. Furthermore, studies directed towards improving the co-catalyst [NADP(H)] consumption of the enzymatic key step by kinetic studies and application of a biphasic reaction medium were performed.

Herein we report on the synthesis of dimeric orsellinates by the Ullmann reaction as well as by biomimetic oxidative phenolic coupling. The Ullmann reaction gives the 5,5Ј-and 3,3Ј-coupled dimeric orsellinates 9 and 10 regioselectively. Oxidative phenolic coupling reaction of methyl 2-hydroxy-4-methoxy-6-methylbenzoate (2) affords the regioisomeric dimeric orsellinates 11 (3,3Ј), 12 (5,5Ј) and 13 (3,5Ј) simultaneously, which can be separated easily by column chromatography. The atropisomers of the 5,5Ј-and 3,3Ј-coupled dimers 9 and 10 were partially resolved using chiral column chromatography. Additionally, the enantiomers of 3,3Ј-