gamma-Pyrones from Gonystylus keithii, as new inhibitors of parathyroid hormone (PTH)-induced Ca release from neonatal mouse calvaria

Andrastin-type meroterpenoids, α-pyrone polyketides, and sesquicarane derivatives from Penicillium sp., a fungus isolated from Pinus koraiensis seed

The genus Penicillium has provided us with the household antibiotic penicillin and the well-known lipid-lowering agent mevastatin. The strain Penicillium sp. SZ-1 was found to grow vigorously in an intact Pinus koraiensis seed, it is inferred that the strain may develop unique mechanisms associated with the biosynthesis of rare metabolites. Further fermentation of the strain on solid rice medium yielded thirteen undescribed compounds, including three andrastin-type meroterpenoids (1-3), two α-pyrone polyketides (4 and 5), and eight sesquicarane derivatives (6-13), along with seven known compounds (14-20). Their structures were determined by detailed analysis of the spectroscopic and spectrometric data (NMR and HRESIMS), in addition to comparisons of the experimental and calculated ECD data for absolute configurational assignments. The hemiacetal moiety in compounds 1 and 2 and the 3α-hydroxy group in compound 3 were rarely found in the andrastin-type meroterpenoid family. The sesquicaranes belong to a small group of sesquiterpenoid that are rarely reported. Bioassay study showed that compound 1 exhibited inhibitory effects against Staphylococcus aureus ATCC 29213 and Escherichia coli ATCC 25922 with MIC values of 64 and 32 μg/mL, respectively. In addition, compounds 1 and 3 displayed weak DPPH radical scavenging activities. The andrastins and sesquicaranes in this study enriched the structural diversity of these classes of terpenoids. Of note, this study is the first report on the metabolites of a fungus isolated from P. koraiensis seed.

Iromycins: A New Family of Pyridone Metabolites from Streptomyces sp. II. Convergent Total Synthesis

The total synthesis of iromycin A (1a), a microbial metabolite combining a novel structure with an interesting biological activity as a NO synthase inhibitor, was accomplished using a flexible and highly convergent approach. Thus, the ring fragment was prepared as 6-bromomethylpyrone 27 by acylation of the respective beta-ketoester 13 and subsequent lactonization of the thus-obtained beta,delta-diketoester 11, followed by bromination of the 6-methyl group. In addition, the unsaturated side chain was efficiently prepared as terminal alkyne 34 which was then carboaluminated to furnish the alkenyldimethylalane 35. The assembly of these two fragments was thoroughly studied using nickel, palladium, and copper catalysts yet only succeeded in the absence of any transition metal after formation of the respective lithium alkenyltrialkylalanate. Treatment of the coupled product 41 with liquid ammonia then completed the total synthesis which furnished an 18% overall yield over the nine steps of the longest linear sequence.

Verticipyrone, a New NADH-fumarate Reductase Inhibitor, Produced by Verticillium sp. FKI-1083

A new NADH-fumarate reductase inhibitor, verticipyrone, was isolated from the cultured broth of a fungus, Verticillium sp. FKI-1083. The structure was established as (E)-2-methoxy-3,5-dimethyl-6-(3-methyl-2-undecenyl)-4H-pyran-4-one. Verticipyrone exhibited an IC50 value of 0.88 nM against NADH-fumarate reductase of Ascaris suum. Verticipyrone inhibited both Ascaris and bovine heart complex I, and its synthetic analogue, 8,9-dihydro-8-hydroxyverticipyrone, showed good selectivity against Ascaris complex I.