Tengerensine (1), isolated as a racemate and constituted from a pair of bis-benzopyrroloisoquinoline enantiomers, and tengechlorenine (2), purified as a scalemic mixture and constituted from a pair of chlorinated phenanthroindolizidine enantiomers, were isolated from the leaves of Ficus fistulosa var. tengerensis, along with three other known alkaloids. The structures of 1 and 2 were determined by spectroscopic data interpretation and X-ray diffraction analysis. The enantiomers of 1 were separated by chiral-phase HPLC, and the absolute configurations of (+)-1 and (-)-1 were established via experimental and calculated ECD data. Compound 1 is notable in being a rare unsymmetrical cyclobutane adduct and is the first example of a dimeric benzopyrroloisoquinoline alkaloid, while compound 2 represents the first naturally occurring halogenated phenanthroindolizidine alkaloid. Compound (+)-1 displayed a selective in vitro cytotoxic effect against MDA-MB-468 cells (IC 7.4 μM), while compound 2 showed pronounced in vitro cytotoxic activity against all three breast cancer cell lines tested (MDA-MB-468, MDA-MB-231, and MCF7; IC values of 0.038-0.91 μM).

Diterpene pyrones (DTPs) are a group of well-known, mainly fungal, natural products, first isolated in 1966.

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Two new diterpene pyrones, asperginols A (1) and B (2), and four known analogues (3–6) were isolated from the endophytic fungus Aspergillus sp. HAB10R12. The structures and absolute configurations of these compounds were elucidated based on the analysis of their NMR, MS, and X-ray diffraction data. The revision of the absolute configurations at C-10, C-11, and C-14 of the known diterpene pyrones (3–6) and the determination of the configuration at the polyene side chain for compounds (4–6) were made using chemical methods and vibrational circular dichroism analysis. This group of diterpene pyrone compounds showed unique structural features including a 7/6/6 tricyclic diterpene moiety with an unusual trans–syn–trans stereochemical arrangement. Compound 6 showed moderate activity against the HT-29 colon cancer cell line.

Investigation of the oxidation of the stilbene succinamide dimer 72 (FeCl3/CH2Cl2) appears, on the basis of spectroscopic evidence, to have produced the bridged macrocyclic indoline 73.

Ternatin and related cyclic peptides inhibit the elongation phase of protein synthesis by targeting the eukaryotic elongation factor-1α (eEF1A), a potential therapeutic vulnerability in cancer and viral infections. The cyclic peptide natural product “A3” appears to be related to ternatin, but its complete structure is unknown and only 4 of its 11 stereocenters have been assigned. Hence, A3 could be any one of 128 possible stereoisomers. Guided by the stereochemistry of ternatin and more potent structural variants, we synthesized two A3 epimers, “SR-A3” and “SS-A3”. We found that synthetic SR-A3 is indistinguishable from naturally derived A3 and potently inhibits cancer cell proliferation. Relative to SS-A3 and previously characterized ternatin variants, SR-A3 exhibits a dramatically enhanced duration of action. This increase in cellular residence time is conferred, stereospecifically, by a single β-hydroxy group attached to N-methyl leucine. SR-A3 thus exemplifies a mechanism for enhancing the pharmacological potency of cyclic peptide natural products via side-chain hydroxylation.

<p>A stereoselective synthesis of the <i>trans</i>-<i>syn</i>-<i>trans </i>perhydrobenzo[<i>f</i>]chromene skeleton is presented. The target compound <b>3 </b>was achieved in six steps starting from the (<i>S</i>)-(+)-Wieland-Miescher ketone. Key steps include the sp² alkylation at the a-carbon of an unsaturated ketone, Birch-type reductive alkylation, and an acid-catalyzed cyclization. </p>

Svalbardines A and B (1 and 2) and annularin K (3) were isolated from cultures of Poaceicola sp. E1PB, an endophyte isolated from the petals of Papaver dahlianum from Svalbard, Norway. Svalbardine A (1) is a pyrano­[3,2-c]­chromen-4-one, a new analogue of citromycetin. Svalbardine B (2) displays an unprecedented carbon skeleton based on a 5′-benzyl-spiro[chroman-3,7′-isochromene]-4,8′-dione core. Annularin K (3) is a hydroxylated derivative of annularin D. The structure of these new polyketides, along with those of known compounds 4–6, was established by spectrometric analysis, including extensive ESI-CID-MS n processing in the case of svalbardine B (2).