Interconversion of the Pallambins through Photoinduced Rearrangement

A new photoinduced interconversion of four naturally occurring 19-<i>nor</i>-7,8-secolabdane diterpenoids was discovered and analyzed. The photochemical mechanism, intramolecular diradical rearrangement reaction, was investigated by time-lapse monitoring of the end product formations with HPLC and UV, as well as detailed theoretical calculations

Pallambins A and B, Unprecedented Hexacyclic 19-<i>nor</i>-Secolabdane Diterpenoids from the Chinese Liverwort <i>Pallavicinia ambigua</i>

Pallambins A (<b>1</b>) and B (<b>2</b>), two novel 19-<i>nor</i>-7,8-secolabdane diterpenoids with unprecedented tetracyclo[4.4.0^3,5.0^2,8]decane skeletons, along with a pair of structurally related isomers, pallambins C (<b>3</b>) and D (<b>4</b>), were isolated from the Chinese liverwort <i>Pallavicinia ambigua</i>. Their structures with absolute configurations were determined by means of NMR, X-ray diffraction, and CD analyses. Their preliminary cytotoxicity to human cancer cells was also tested

Pallambins A and B, Unprecedented Hexacyclic 19-<i>nor</i>-Secolabdane Diterpenoids from the Chinese Liverwort <i>Pallavicinia ambigua</i>

Pallambins A (<b>1</b>) and B (<b>2</b>), two novel 19-<i>nor</i>-7,8-secolabdane diterpenoids with unprecedented tetracyclo[4.4.0^3,5.0^2,8]decane skeletons, along with a pair of structurally related isomers, pallambins C (<b>3</b>) and D (<b>4</b>), were isolated from the Chinese liverwort <i>Pallavicinia ambigua</i>. Their structures with absolute configurations were determined by means of NMR, X-ray diffraction, and CD analyses. Their preliminary cytotoxicity to human cancer cells was also tested

Heptaketides from an Endolichenic Fungus <i>Biatriospora</i> sp. and Their Antifungal Activity

Twelve new heptaketides, biatriosporins A–L (<b>1</b>–<b>12</b>), biatriosporin M (<b>13</b>) (a ramulosin derivative), and 19 known compounds (<b>14</b>–<b>32</b>) were isolated from the endolichenic fungus <i>Biatriospora</i> sp. (8331C). The structures of these compounds were determined by analyzing MS and NMR data. The absolute configurations of compounds <b>1</b>, <b>2</b>, <b>7</b>, and <b>9</b> were determined by single-crystal X-ray diffraction analysis, whereas compound <b>10</b> was deduced with Mosher’s method. Four of the compounds were active in an antifungal assay. The most potent compound, compound <b>4</b>, also sensitized clinically derived azole-resistant <i>Candida albicans</i> strains to fluconazole (FLC). A mechanistic investigation revealed that <b>4</b> inhibited the function of efflux pumps and reduced the transcriptional expression of the efflux-pump-related genes <i>CDR1</i> and <i>CDR2</i>

Two new cadinane-type sesquiterpenes from the Chinese liverwort <i>Frullania serrata</i>

<div><p>Two new cadinane-type sesquiterpenes, frullanic acid (<b>1</b>) and frullanic acid methyl ester (<b>2</b>), together with four known bibenzyls, brittonin B (<b>3</b>), 3,3′-dimethoxy-4,5-methylenedioxybibenzyl (<b>4</b>), 3,4,5,3′,4′-penlamethoxybibenzyl (<b>5</b>) and ( ± )-3-(4′-methoxybenzyl)-5,6-dimethoxyphtbalide (<b>6</b>), were isolated from the Chinese liverwort <i>Frullania serrata</i>. The structures of the new metabolites were elucidated by analysing the spectroscopic data (1D NMR, 2D NMR, HR-ESI-MS and IR). The absolute configurations of compounds <b>1</b> and <b>2</b> were determined by comparing the experimental and calculated electronic circular dichroism spectra predicted by using time-dependent density functional theory as well as the CD exciton chirality method.</p></div

Notolutesins A–J, Dolabrane-Type Diterpenoids from the Chinese Liverwort <i>Notoscyphus lutescens</i>

Ten new dolabrane-type diterpenoids, notolutesins A–J (<b>1</b>–<b>10</b>), were isolated from the Chinese liverwort <i>Notoscyphus lutescens</i>, along with four known compounds. The structures of the new compounds were established on the basis of extensive spectroscopic data, and that of <b>1</b> was confirmed by single-crystal X-ray crystallography. The absolute configuration of <b>1</b> was determined by comparing its experimental and calculated electronic circular dichroism spectra. All of the isolates were evaluated for their cytotoxicity against a small panel of human cancer cell lines, and compound <b>1</b> exhibited an IC₅₀ value of 6.2 μM against the PC3 human prostate cancer cell line

Notolutesins A–J, Dolabrane-Type Diterpenoids from the Chinese Liverwort <i>Notoscyphus lutescens</i>

Ten new dolabrane-type diterpenoids, notolutesins A–J (<b>1</b>–<b>10</b>), were isolated from the Chinese liverwort <i>Notoscyphus lutescens</i>, along with four known compounds. The structures of the new compounds were established on the basis of extensive spectroscopic data, and that of <b>1</b> was confirmed by single-crystal X-ray crystallography. The absolute configuration of <b>1</b> was determined by comparing its experimental and calculated electronic circular dichroism spectra. All of the isolates were evaluated for their cytotoxicity against a small panel of human cancer cell lines, and compound <b>1</b> exhibited an IC₅₀ value of 6.2 μM against the PC3 human prostate cancer cell line