Chevalinulins A (1) and B (2), two indole diketopiperazine alkaloids containing an unprecedented spiro­[bicyclo[2.2.2]­octane-diketopiperazine] skeleton, together with a known analogue neoechinulin B (3), were isolated from the deep-sea cold-seep-derived fungus Aspergillus chevalieri CS-122. Their structures were determined by spectroscopic analysis, single-crystal X-ray diffraction, specific rotation (SR), and NMR calculations. Compounds 1 and 2 exhibited significant in vivo proangiogenic activity in transgenic zebrafish.

Determination of the stereochemistry of organic molecules still represents one of the major obstacles in the structure elucidation procedure in drug discovery. Although the application of residual dipolar couplings (RDCs) has revolutionized this field, residual chemical shift anisotropies (RCSAs) which contain valuable structural information for nonprotonated carbons have only been scarcely employed so far. In this study, we present a simple but highly effective solution to extract RCSAs of the analytes in a liquid crystalline phase formed by AAKLVFF oligopeptides. This method does not require any special instruments, devices, or correction during postacquisition data analysis and thus can be easily applied in any chemistry laboratory. To illustrate the potential of this method, the relative configurations of four known natural products (1−4) belonging to different structural classes were confirmed. Moreover, we unambiguously elucidated the stereochemistry of spiroepicoccin A (5), a rare thiodiketopiperazine marine natural product whose configuration could not be assigned based on conventional NMR methods.

A new cytochalasin dimer, verruculoid A (1), three new cytochalasin derivatives, including 12-nor-cytochalasin F (2), 22-methoxycytochalasin B6 (3), and 19-hydroxycytochalasin B (4), and 20-deoxycytochalasin B (5), a synthetic product obtained as a natural product for the first time, together with four known analogues (6–9), were isolated and identified from the culture extract of Curvularia verruculosa CS-129, an endozoic fungus obtained from the inner fresh tissue of the deep-sea squat lobster Shinkaia crosnieri, which was collected from the cold seep area of the South China Sea. Structurally, verruculoid A (1) represents the first cytochalasin homodimer containing a thioether bridge, while 12-nor-cytochalasin F (2) is the first 12-nor-cytochalasin derivative. Their structures were elucidated by detailed interpretation of the NMR spectroscopic and mass spectrometric data. X-ray crystallographic analysis and ECD calculations confirmed their structures and absolute configurations. Compound 1 displayed activity against the human pathogenic bacterium Escherichia coli (MIC = 2 μg/mL), while compounds 4, 8, and 9 showed cytotoxicity against three tumor cell lines (HCT-116, HepG-2, and MCF-7) with IC50 values from 5.2 to 12 μM. The structure–activity relationship was briefly discussed.