Asteriscane-Type Sesquiterpenoids from the Soft Coral Sinularia capillosa

Abstract

Chemical examination of the soft coral Sinularia capillosa collected from the South China Sea resulted in the isolation of 14 new asteriscane-type sesquiterpenoids, namely, capillosananes A-N (1-14), four new seco-asteriscanes, capillosananes O-R (15-18), and (-)-sinularone A and sinularone A. Their structures were determined on the basis of extensive spectroscopic analyses, while the absolute configurations were determined by CD and ECD calculation, Mosher's method, and chemical conversion. This is the first report of asteriscane-type sesquiterpenoids from soft corals, and capillosananes Q (17) and R (18) represent new seco-asteriscane skeletons. Capillosanane A exhibited potent antifouling activity against Balanus amphitrite, with an IC₅₀ value of 9.70 μM, while capillosananes B and I and (-)-sinularone A inhibited inflammation-related TNF-α in vitro.

Chemical constituents of the soft corals Sinularia vanderlandi and Sinularia gravis from the coast of Madagascar

“…72 In addition, there is a full agreement of the 13 C NMR data of (−)-(R)-nephthenol (7) from S. gravis with those from a sample isolated from the soft coral Litophyton arboreum 42 (Table S7 †). (−)-(R)-Nephthenol (7) has been isolated first from Nephthea sp. 37 and later also from Lithophyton arboreum, 42,43 Lobophytum pauciflorum, 43 Sarcophyton decaryi, 38,44 and Sinularia erecta.…”

Cembranoids from a Chinese Collection of the Soft Coral Lobophytum crassum

“…In addition, the coupling pattern of H-7 (δ H 3.58 d, J = 10.8 Hz) indicated its axial orientation (one large coupling due to dihedral angles of approximately 180° and 90° with the H 2 -6 protons), while the NOE correlations of H-7/H 3 -19, H-7/H-10a, and H 3 -19/H-10a suggested the same orientation of H-7, H 3 -19, and H-10a. Furthermore, the absolute configuration of the 7,8-diol was determined by an in situ dimolybdenum CD method [ 31 , 32 ], based on which the sign of the induced CD (ICD) bands at 310, 350, and 400 nm reflected the O-C-C-O torsion angle. After addition of dimolybdenum tetraacteate [Mo 2 (OAc) 4 ] into a DMSO solution of 3 , a metal complex was generated immediately and the ICD spectrum was acquired.…”

Gold(I)/Copper(II)‐Cocatalyzed Tandem Cyclization/Semipinacol Reaction: Construction of 6‐Aza/Oxa‐Spiro[4.5]decane Skeletons and Formal Synthesis of (±)‐Halichlorine

“…Especially with the rapid development of certain disciplines such as chemical biology and pharmaceutical chemistry, and the appearance of modern techniques,2 there has been significant growth in the demand for bioactive natural products and their derivatives. Aza/oxa ‐spirocyclic skeletons, as key structural moieties, broadly exist in a number of bioactive natural products, such as capillosanane Q, capillosanane I,3 cephalotaxin,4 pinnaic acid,5 and halichlorine6, 7 (Figure 1). Because of the special bioactivity and structural complexity of these molecules, particularly their potential for future drug discovery, strategies toward the syntheses of the relevant aza/oxa ‐spirocyclic skeletons have attracted the attention of organic chemists.…”

“…As shown in Table 1, in the initial tests using common p-acids, such as AuCl and PtCl 2 , only the use of AuCl could afford the desired spirocyclic product 2 a in a very low yield of 9 %, and most of 1 a was recovered. [16] Fortunately, when [PPh 3 AuCl]/AgOTf (1:1) was used as the catalyst, 2 a could be obtained in a slightly higher yield of 15 %. Based on this information and our previous experience with the semipinacol type vinylogous a-ketol rearrangements, [17] we assumed that the presence of another Lewis/Brønsted acid might better promote the reaction by coordinating to the carbonyl group ultimately leading to a better outcome.…”

“…Following this speculation, we observed that the addition of p-TsOH (10 mol %) into the reaction system clearly improved the yield of 2 a, and the use of p-TsOH/[PPh 3 AuCl]/ AgBF 4 (1:1:1) gave a yield of 28 % in CH 2 Cl 2 . Additionally, the reactivity difference between AuCl and [PPh 3 AuCl]/AgOTf (1:1) further prompted the evaluation of the corresponding ligand effect. [18] Accordingly, it was found that changing the ligand to BINAP could further increase the yield of 2 a to 47 %.…”