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. 2019 Apr 26;17(5):250.
doi: 10.3390/md17050250.

Structures and Absolute Configurations of Diketopiperazine Alkaloids Chrysopiperazines A⁻C from the Gorgonian-Derived Penicillium chrysogenum Fungus

Wei-Feng Xu  1   2 , Ning Mao  3   4 , Xiao-Jia Xue  5   6 , Yue-Xuan Qi  7   8 , Mei-Yan Wei  9   10   11 , Chang-Yun Wang  12   13 , Chang-Lun Shao  14   15
Affiliations

Structures and Absolute Configurations of Diketopiperazine Alkaloids Chrysopiperazines A⁻C from the Gorgonian-Derived Penicillium chrysogenum Fungus

Wei-Feng Xu et al. Mar Drugs. .

Abstract

Three new diketopiperazine alkaloids, including two oxepine-containing diketopiperazines, chrysopiperazines A and B (1 and 2), and one quinazoline-containing diketopiperazine, chrysopiperazine C (5), together with three known analogues (3, 4, and 6), were isolated from the gorgonian-derived Penicillium chrysogenum fungus. The relative and absolute configurations of C-3 and C-15 in 1 and 2, C-3 and C-14 in 5 were established by NOE modified Marfey's analysis and electronic circular dichroism (ECD) calculations. Particularly, the absolute configurations of C-19 in 1 and 3, which was very challenging to be identified due to the flexible conformation in a short aliphatic chain, were successfully determined by the vibrational circular dichroism (VCD) method, supplying with a reliable and optional method to define the absolute configurations. Additionally, this is the first report on oxepine-containing diketopiperazines from the genus Penicillium.

Keywords: Penicillium chrysogenum; VCD method; absolute configurations; diketopiperazine alkaloids; oxepine‐containing.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Chemical structures of 1–6.
Figure 2
Figure 2
Key 1H− 1H COSY (bold) and HMBC (arrows) correlations of 1, 2, and 5.
Figure 3
Figure 3
Key NOE correlations of 1, 2, and 5.
Figure 4
Figure 4
Experimental and calculated VCD/IR spectra of 1.
See this image and copyright information in PMC

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