The Structure of a Novel Cembranoid Diterpene from a Philippine Collection of the Soft Coral Sinularia flexibilis

Abstract

A new optically active diterpene lactone, sinulariolone [1], has been isolated as the major secondary metabolite in a Philippine collection of Sinularia flexihilis. The compound has a tricyclic structure and is more highly oxygenated than previously reported diterpenes from this species. The structure of 1 was elucidated by spectroscopy and its relative stereochemistry confirmed by single-crystal X-ray crystallography.

Oxygenated Cembranoids from the Cultured and Wild-Type Soft Corals Sinularia flexibilis

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In previous studies a series of novel secondary metabolites, including cembranes, [1][2][3][4][5][6][7][8][9][10][11][12] eunicellin-based compounds, 13) and other metabolites, [14][15][16][17] have been isolated from the soft coral Sinularia flexibilis (Quoy and Gaimard). Some of these were found to exhibit cytotoxic activity against the growth of various cancer cell lines.

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Dendronpholides A−R, Cembranoid Diterpenes from the Chinese Soft Coral Dendronephthya sp.

“…These findings suggested that the methoxy group was linked to C-13. This assignment was confirmed by the HMBC relationship between the methoxy protons and C- 13 and,in turn,d,J ) 10.5 Hz) to the carbons at δ C 60. 2 (MeO),, and 30.…”

Cembrane Diterpenes Chemistry and Biological Properties

“…Four new cembranoid diterpenes, 11,12-epoxy-1(E),3(E),7(E)-cembratrien-15-ol (117), 3,4:11,12-diepoxy-15-methoxy-1(E),7(E)-cembradiene (118), 1(E),3(E),7(E),11(E)-cembratetraene-14,15-diol (119), and 3,14-epoxy-1(E),7(E),11(E)-cembratriene-4,15-diol (120), have been isolated from the soft coral Sinularia gibberosa [42]. A series of analogs were isolated from the soft coral Sinularia flexibilis (121) [43], Sinularia gibberosa (122) [44], Sarcophyton decaryi (123,124) [45,46], Nephthea brassica (125) [47], Lobopbytum pauciflorum (126)(127) [20,48], Sarcophyton mililatensis (130) [49]. Three novel cembrane diterpenoids, decaryiols B-D (130-132), characterized by a bicyclic skeleton of the decaryiol-type, have been isolated from the Indonesian soft coral Lobophytum sp., meanwhile, a analogue, namely decaryiol (133), have been isolated from the soft coral Sarcophyton decaryi [50].…”

“…Chromatographic investigation of the octocoral Sinularia flexibilis afforded eight new diterpenes, sinuladiterpenes A-H (406-413), Compound 407 exhibited in vitro cytotoxic activity against human colon adenocarcinoma (WiDr) cell line with ED 50 8.37 μg/ml [69,121]. Moreover, a series of analogs were also isolated from Sinularia flexibilis, including sinulaflexiolides B-D, J, and K (414-418) [43], flexilarins D-J (419-425) [70], sinulariolone (426) [122], sandensolide monoacetate (427) and flexibolide (428) [123], and sinulariolide (429) [124]. Sinulaflexiolides D (416) showed selective inhibitory activity against the gastric gland carcinoma cell line BGC-823 at 8.5 μM.…”