Studies of Australian Soft Corals. XLII. Structure Determination of New Briaran Derivatives From Briareum steckei (Coelenterata, Octocorallia, Gorgonacea)

Abstract

The structure and relative stereochemistry of four new metabolites from Briareum steckei has been deduced from 2D-n.m.r. experiments at high field, and confirmed by a single-crystal X-ray determination of a minor metabolite. The new compounds are non-halogenated briaran derivatives: (1R*,2S*,3R*,5Z,7S*,8(17)Z,l0R*, llR *,12S*,14S*)- 3,14-diacetoxy- 11,12-epoxy- 18-oxobriara-5,8(17)-dien-2-yl butanoate (3), its 3-deacetoxy derivative (4), (1R*,2R*,4R*,5Z,7S*,8(17)Z,10R*, 11R *,12S*,14S*)-4,14-diacetoxy-11,12-epoxy-18-oxobriara-5,8(17)-dien-2-yl butanoate (5) and the related 2-propanoate (6). Single-crystal X-ray determinations were performed on (5) and (6).

Excavatolides U−Z, New Briarane Diterpenes from the Gorgonian Briareum excavatum

“…25 Suitable colorless prisms of 1 were obtained from a solution in EtOAc. The crystal (0.48 × 0.68 × 0.72 mm) belongs to the monoclinic system, space group P212121 with a ) 11.169(1) Å, b ) 15.072(2) Å, c ) 20.123(2) Å, V ) 3387.5(6) Å 3 , Z ) 4, Dcalcd ) 1.276 g/cm 3 , λ (Mo KR) ) 0.71069 Å. Intensity data were measured on Rigaku AFC6S diffractometer up to 2θ of 25.0°.…”

“…In the past decade, a large number of highly oxygenated diterpenoids, such as briaranes and asbestinins, have been discovered from the gorgonian corals of the genus Briareum (family Briareidae, order Gorgonacea, phylum Cnidaria), 1 which is placed taxonomically within the order Alcyonacea or Gorgonacea, [2][3][4] and has been reported under the synonym Solenopodium. 5 In the course of our search for new bioactive substances for potential biomedical uses from the Formosan marine invertebrates, the briarane-type diterpenes continue to be the target of our investigations because of the interesting biological activities (e.g., toxic, [6][7][8] cytotoxic, 4,9-15 antiinflammatory, [16][17][18] antiviral, 9,16 insecticidal, 19,20 antifouling, 21 immunodulatory, 22 and antibacterial 23 ) associated with the compounds of this type.…”

“…Previous investigations on the chemical constituents on B. excavatum (Nutting) have resulted in the isolation of 20 diterpenes, excavatolides A-T, possessing the briarane carbon skeleton. 14,15,24 Our continuing investigation of the secondary metabolites of B. excavatum has led to the isolation and structure elucidation of six new briarane diterpenes, excavatolides U-Z (1)(2)(3)(4)(5)(6). The structures and relative stereochemistry of compounds 1-6 were established by the use of a series of 2D NMR experiments ( 1 H-1 H COSY, HMQC, HMBC, and NOESY) and chemical transformations.…”

Marine natural products

“…The absolute configuration of manoalide (275), which is an antiinflammatory agent from Luflariella ~a r i a b i l i s , ~~~ has been determined by total synthesis of a derivative from 2-deoxy-~-An additional synthesis of manoalide (275), which involves the intermediacy of seco-manoalide (276), has been outlined. 226 The total synthesis of dysideapalaunic acid (277), which is an unreported( !) aldose reductase inhibitor from a Palauan species of Dysidea, has established the absolute c~nfiguration.~~' The structure of suvanine, which is an acetyl cholinesterase inhibitor from a species of Coscinoderma found in both Fiji and Palau, has been revised from (278)228 to (279).…”

Briarenolides K and L, New Anti-Inflammatory Briarane Diterpenoids from an Octocoral Briareum sp. (Briareidae)

“…The octocorals belonging to the genus Briareum (phylum Cnidaria, class Anthozoa, subclass Octocorallia, order Gorgonacea, suborder Scleraxonia, family Briareidae) have been proven to be the most important source of briarane analogues [ 1 , 2 , 3 , 4 , 5 ]. The genus Briareum is distributed widely in the Indo-Pacific Ocean and the Caribbean Sea and is placed taxonomically within the orders Gorgonacea and Alcyonacea [ 8 , 9 , 10 , 11 ]. Previous chemical investigations of octocorals belonging to the genus Briareum , collected off the waters of Taiwan, at the intersection of the Kuroshio current and the South China Sea surface current, have yielded numbers of briarane analogues [ 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ].…”