Abstract
Two new steroids, crellasterones A (1) and B (2), together with the previously reported compound chalinasterol (3) and several nucleosides (4–7), were isolated from the sponge Crella incrustans, collected in New Caledonia. The structures of the new compounds were established by extensive NMR and mass spectroscopic analysis and revealed unprecedented marine natural products with a ring-contracted A-norsterone nucleus and 2-hydroxycyclopentenone chromophore. The absolute configurations were derived from electronic circular dichroism (ECD) measurements in conjunction with high-level density functional theory (DFT) calculations.
Highlights
Sterols [1] are among the most studied groups of natural products, with interest commencing in the 19th century, running through to the 1969 Nobel Prize in Chemistry for Sir Derek Barton, and continuing to the present day
Norselic acid A [12] is an anti-infective steroid isolated from the Antarctic sponge Crella sp. that possesses antibiotic activity against methicillin-resistant Staphylococcus aureus (MRSA), methicillin-sensitive S. aureus (MSSA), vancomycin-resistant Enterococcus faecium (VRE), and Candida albicans [12]
The frozen sponge was exhaustively extracted with ethanol to afford an extract that was successively partitioned with n‐hexane/aqueous ethanol, ethyl acetate/aqueous ethanol and n‐
Summary
Sterols [1] are among the most studied groups of natural products, with interest commencing in the 19th century, running through to the 1969 Nobel Prize in Chemistry for Sir Derek Barton, and continuing to the present day. Sponges from the genus Crella have not been widely studied, with only a few natural products isolated, including crellastatins A–M, [8,9,10] shishicrellastatins A and B [11], norselic acids A–E [12] and benzylthiocrellidone [13]. Crellastatins B–M exhibit in vitro antitumor activity against NSCLC cell lines with IC50 values of 1–10 μg/mL [9,10]. Norselic acid A [12] is an anti-infective steroid isolated from the Antarctic sponge Crella sp. Structures of compounds isolated from Crella incrustans (1–7) in the current study and Scheme 1. Structures of compounds isolated from Crella incrustans (1–7) in the current study and related compounds (8–9)
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