Determination of the Absolute Configuration of Super-Carbon-Chain Compounds by a Combined Chemical, Spectroscopic, and Computational Approach: Gibbosols†A and B.

Marine dinoflagellates produce remarkable organic molecules, particularly those with polyoxygenated long-carbon-chain backbones, namely super-carbon-chain compounds (SCCCs), characterized by the presence of numerous stereogenic carbon centers on acyclic polyol carbon chains. Even today, it is a challenge to determine the absolute configurations of these compounds. In this work, the planar structures and absolute configurations of two highly flexible SCCCs, featuring either a C69 - or C71 -linear carbon backbone, gibbosols A and B, respectively, each containing thirty-seven stereogenic carbon centers, were unambiguously established by a combined chemical, spectroscopic, and computational approach. The discovery of gibbosols A and B with two hydrophilic acyclic polyol chains represents an unprecedented class of SCCCs. A reasonable convergent strategy for the biosynthesis of these SCCCs was proposed.

Two new biflavonones from Coreopsis tinctoria.

Two new biflavonone compounds, sikokianin D (1) and sikokianin E (2), were isolated from the capitulum of Coreopsis tinctoria. The structures of these compounds were elucidated by spectroscopic techniques including NMR, HRESIMS and circular dichroism (CD).

Phomopsols A and B from the Mangrove Endophytic Fungus Phomopsis sp. xy21: Structures, Neuroprotective Effects, and Biogenetic Relationships.

A polyketide-derived alkaloid featuring a unique 3,4-dihydro-2H-indeno[1,2-b]pyridine 1-oxide motif, named phomopsol A (1), and a highly oxidized polyketide containing a new 3,5-dihydro-2H-2,5-methanobenzo[e][1,4]dioxepine moiety, named phomopsol B (2), were isolated from the Thai mangrove endophytic fungus Phomopsis sp. xy21, together with the related biosynthetic polyketide 3. The structures of 1-3 were unambiguously established by single-crystal X-ray diffraction analysis (Cu Kα), and their neuroprotective effects in PC12 cells were evaluated. The biosynthetic origins of 1-3 are proposed.

A new caffeic acid tetramer from the Dracocephalum moldavica L.

A new caffeic acid tetramer compound, named (+) methyl rabdosiin (4), together with seven known caffeic acid multimers (1-3, 5-8) and one caffeic acid monomer (9), were isolated from the aerial parts of Dracocephalum moldavica L. The structures of these compounds were assigned on the basis of 1D and 2D NMR spectroscopic and mass spectrometry analyses. The protective effects of compounds 2-4 against hydrogen peroxide (H2O2)-induced apoptosis were evaluated in primary cardiomyocytes of SD neonatal rats in vitro by the MTT method. Three compounds exhibited potent protective activities at 12.5 µg/mL.