Sorrentanone

In our screening of microorganisms for new natural products, the fungus Penicillium notatum delivered further members of the sorbicillin family, namely, the sohirnones A [3, 1-(2,4-dihydroxy-5-methylphenyl)hex-4-en-1-one], B [4a, 1-(2,4,5-trihydroxy-3,6-dimethylphenyl)hexa-2,4-dien-1-one], and C [5, 1-(2,4,5-trihydroxy-3,6-dimethylphenyl)hex-4-en-1-one]. A stable tautomer of oxosorbicillinol (7) was characterized as 6, and the recently described 7-deacetoxyyanuthone (8) was reisolated. The additionally isolated rezishanones A-D (12-13c) are the first natural Diels-Alder products of sorbicillinol (1) with dienophiles not related with 1. The monomers and dimers showed weak antibacterial activity, but were inactive against fungi and algae. The structures were determined by spectroscopic methods and by comparison of the NMR data with those of the structurally related 2',3'-dihydrosorbicillin (2) and, in the case of 4a, by transformation into the known sorrentanone (4b).

The sorbicillinoids are a large family of fungal natural products, many of which possess highly challenging molecular architectures. Depending on their individual structures they exhibit strong biological activities ranging from radical scavenging and anti-infective properties to cytotoxicity. Despite the resulting strong biomedical potential of these natural products and the interest of synthetic chemists owing to their fascinating structures, many sorbicillinoids are currently not synthetically accessible, thus hampering in-depth biological characterization and structural diversification. By using recombinant oxidoreductase SorbC and readily accessible sorbicillin-type synthetic precursors, we have developed enantioselective, one-pot chemo-enzymatic routes to a broad range of sorbicillinoids, thereby establishing total syntheses of oxosorbicillinol, sorrentanone, rezishanones B and C, sorbicatechol A, bisvertinolone, and (+)-epoxysorbicillinol.