Pestalotiopsin C, stereochemistry of a new caryophyllene from a fungus of Trichoderma sp. and its tautomerization characteristics in solution

A new pestalotiopsin C (1) with three known compounds (2–4) are obtained from the fermentation broth of fungus of Trichoderma KK19L1 sp. Pestalotiopsin C (1) has two atropisomers with mole ratio of 1.2/1 in chloroform at room temperature. Its structure was well established by 1D and 2D NMR, and further confirmed by X-ray diffraction. Its absolute configuration (AC) was determined by comparing its experimental electronic circular dichroism (ECD) and optical rotation (OR) value with the calculated ECD and OR data using quantum methods. The bioactivity of compound 1 was tested against five cell-lines HL-60, SMMC-7721, A-549, MCF-7, SW480, respectively.