17-Hydroxybrevianamide N and Its N1-Methyl Derivative, Quinazolinones from a Soft-Coral-Derived sp. Fungus: 13 Enantiomers as the True Natural Products.

Under the guidance of MS/MS-based molecular networking and HPLC-UV, two new alkaloid racemates, (±)-17-hydroxybrevianamide N () and (±)-N1-methyl-17-hydroxybrevianamide N (), featuring a rare -hydroxyphenylalanine residue and an imide subunit, were isolated from a soft-coral-derived sp. fungus. The true natural products (+)- and (+)- were further monitored and obtained from the freshly prepared EtOAc extracts, while (-)- and (-)- are artifacts generated during extraction and purification processes. Simultaneously, the structures including absolute configurations of (+)-13-, (-)-13-, (+)-13-, and (-)-13- were elucidated on the basis of comprehensive spectroscopic analysis, ECD calculations, and X-ray diffraction data. Interestingly, basic solution promotes the racemization of (+)- and (-)-, whereas acidic solution suppresses the transformation. The current research was concerned with the true natural products and their artifacts, providing critical insight into the isolation and identification of natural products.