**1. Introduction**

Biologically active trisulfated steroids are characteristic secondary metabolites found in some marine sponges. These polar steroids comprise several structural subgroups in the sponges. The first compound, bearing a common 2β,3α,6α-trisulfoxy steroid nucleus, halistanol sulfate, was isolated in 1981 from the Okinawan sponge *Halichondria* cf. *moorei* [1] (Figure S1). The subgroup also includes sokotrasterol sulfate from the sponge *Halichondria* sp. [2], halistanol sulfates A-J and polasterol B, found in the sponges *Epipolasis* sp. [3,4], *Pseudoaxinissa digitata* [5], and *Halichondria* sp. [6], ophirapsranol trisulfate from *Topsentia ophiraphidites*[7], four sterols isolated from the sponges *Trachyopsis halichondroides* and *Cymbastela coralliophila* [8], amaranzoles A-F from *Phorbas amaranthus* [9,10], and topsentinol K trisulfate from the sponge *Topsentia* sp. [11]. Another subgroup of these metabolites consists of ibisterol sulfates and lembesterol A from the sponges *Topsentia* sp. [12], *Xestospongia* sp. [13], and *Petrosia strongilata* [14]. In their steroid nuclei, 2β,3α,6α-trisulfoxy functionality is combined with a C-9(11)-double bond and a methyl group at C-14. One more subgroup includes topsentiasterol sulfates A–E from the sponge *Topsentia* sp. [15], Sch 575867 from the deep-water sponge belonging to the family Astroscleridae [16], spheciosterol sulfates from the sponge *Spheciospongia* sp. [17], as well as chloro- and iodotopsentiasterol sulfates D, isolated from the sponge *Topsentia* sp. in our laboratory [18]. These compounds contain a common Δ9(11)-unsaturated, 4β-hydroxy-14α-methyl, 2β,3α,6α-trisulfated steroid nucleus.

In addition to unusual structural features, trisulfated steroids possess promising biological properties [19]. In fact, a broad range of activities has been described to trisulfate steroids such as antibacterial [1,15,20], antifungal [15,16,21], antiviral (including anti-HIV and anti-HSV effects) [5,12,13,22,23], antiparasitic [21], and antiplatelet activities [24]. In addition, the inhibition of different enzymes [6,11,18], promotion of angiogenesis [25], and antitumor activity against various tumor cell lines [7,15,17,26] have been described. Thus, the search for new trisulfated steroids from sponges, including the analyses of their chemical structures and physiological properties, continues to be a promising area of research. Hopefully, this may lead to the development of a new generation of drugs for a broad spectrum of diseases.

In the course of our ongoing interest in new biologically active secondary metabolites of marine invertebrates, *Halichondria vansoesti* sponge, collected in Vietnamese waters during the 49th scientific cruise aboard the R/V 'Academic Oparin', was investigated. As a result, ten trisulfated steroids **1**–**10** were isolated (Figure 1). Using NMR spectroscopy, including 1H, 13C, HSQC, COSY, HMBC, and NOESY, as well as high-resolution mass spectrometry and chemical transformations, **1**–**4** and **8**–**10** were identified as new, unusual analogues of topsentiasterol sulfates and halistanol sulfates. Compounds **5**–**7** were previously known as chlorotopsentiasterol sulfate D, iodotopsentiasterol sulfates D [18], and topsentiasterol sulfate D, respectively [15]. Herein, we report the isolation, structural elucidation, proposed biosynthetic pathways, and the study of the biological activities of the isolated compounds.

**Figure 1.** The structures of **1**−**10**.
