*3.1. General Experimental Procedures*

Optical rotations were measured on Perkin-Elmer 343 digital polarimeter (Perkin Elmer, Waltham, MA, USA). UV-spectra were registered on a Shimadzu UV-1601PC spectrophotometer (Shimadzu Corporation, Kyoto, Japan). ECD spectra were obtained on a Chirascan plus instrument (Applied Photophysics Ltd., Leatherhead, UK). 1H-NMR (500.13 MHz, 700.13 MHz) and 13C-NMR (125.75 MHz, 176.04 MHz) spectra were recorded in CDCl3 on Bruker Avance III HD 500 and Bruker Avance III 700 spectrometers (Bruker BioSpin, Bremen, Germany). The 1H- and 13C-NMR chemical shifts were referenced to the solvent peaks at δ<sup>H</sup> 7.26 and δ<sup>C</sup> 77.0 for CDCl3. HRESIMS analyses were performed using a Bruker Impact II Q-TOF mass spectrometer (Bruker). The operating parameters for ESI were as follows: a capillary voltage of 3.5 kV, nebulization witH-Nitrogen at 0.8 bar, dry gas flow of 7 L/min at a temperature of 200 ◦C. The mass spectra were recorded within *m/z* mass range of 100–1500. The instrument was operated using the otofControl (ver. 4.1, Bruker Daltonics) and data were analyzed using the DataAnalysis Software (ver. 4.4, Bruker Daltonics). Column chromatography was performed on Sephadex LH-20 (25–100 μm, Pharmacia Fine Chemicals AB, Uppsala, Sweden), silica gel (KSK, 50–160 mesh, Sorbfil, Krasnodar, Russia) and YMC ODS-A (12 nm, S-75 um, YMC Co., Ishikawa, Japan). HPLC were carried out using an Agilent 1100 Series chromatograph equipped with a differential refractometer (Agilent Technologies, Santa Clara, CA, USA). The reversed-phase columns YMC-Pack ODS-A (YMC Co., Ishikawa, Japan, 10 mm × 250 mm, 5 μm and 4.6 mm × 250 mm, 5 μm) and Discovery HS F5-5 (SUPELCO Analytical, Bellfonte, PA, USA, 10 mm

× 250 mm, 5 μm) were used for HPLC. Yields are based on dry weight (212.1 g) of the sponge sample.

#### *3.2. Animal Material*

The *Stelletta* sp. sponge sample (wet weight 1.3 kg) was collected by SCUBA diving at the depth of 7–12 m near Cham Island (15◦54.3- N, 108◦31.9- E) in the Vietnamese waters of the South China Sea during the 038-th cruise of R/V "Academik Oparin" in May 2010. The species was identified and described [14] by Dr. Boris B. Grebnev from G. B. Elyakov Pacific Institute of Bioorganic Chemistry, FEB RAS (PIBOC, Vladivostok, Russia). A voucher specimen (PIBOC O38-301) has been deposited at the collection of marine invertebrates in PIBOC.
