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The alcyonacean soft coral Sinularia flexibilis Quoy and Gaimard produces a number of bioactive complementary (secondary) metabolites. The ability of three of these diterpenes — flexibilide, sinulariolide and dihydroflexibilide — to elicit differential discriminatory feeding behavior in Gambusia affinis was assessed in a feeding deterrence study. Terpene-impregnated fish flakes were offered to fish trained to feed on such food, and their responses (acceptance, rejection, avoidance, or no response) were assessed as indicative of feeding deterrence. Food treated with sinulariolide (a compound previously determined to be non-bioactive) was generally accepted at a 1% concentration. It was avoided and rejected, however, at a concentration of 10%, a concentration level generally restricted to polyp-rich branchlets. This indicated negative olfactory and palatability cues, respectively. Flexibilide-treated flakes were accepted to some extent by the fish at the 1% concentration, but strongly avoided at the 10% concentration, indicating effective feeding deterrence via olfaction. Dihydroflexibilide-impregnated flakes were strongly rejected even at low concentrations (1%) after tasting, indicating a negative palatibility cue. They were strongly avoided or rejected at higher concentrations (10%), indicating a negative olfactory cue as well. This response at higher concentrations indicates that sinulariolide and flexibilide become effective at concentrations between 1% and 10%. Such concentrations may be found in the polypary (polyp-bearing portion) of the soft coral colonies. Dihydroflexibilide elicited the strongest negative palatability response from these test fish. The feeding deterrence characteristics of the compounds determined here represent the potentials of individual compounds to elicit differential feeding responses in organisms like Gambusia which are capable of discriminating between different but closely related complementary (secondary) metabolites.

The structure and relative stereochemistry of three new eunicellin-based diterpenoids (2), (3) and (4) from a Cladiella sp. of soft coral have been determined by spectral evidence and confirmed by chemical interconversion.

Two new fatty acid methyl esters having an enone ether group were isolated from the root bark of Hibiscus rosa-sinensis along with three known cyclopropenoids. The new compounds, methyl ( E )-11-methoxy-9-oxo-10-nonadecenoate and ( E )-10-methoxy-8-oxo-9-octadecenoate, were chemically correlated to the corresponding cyclopropenoids. propenoids.

Denticulatolide, an ichthyotoxic cembranoid diterpene bearing acetoxy, α-methylene γ-lactone, and cyclic peroxide functions, has been isolated from the soft coral Lobophytum denticulatum. The structure (1) has been determined by spectral and chemical evidence and X-ray crystallographic method.

A novel reaction of ketone enolate with dimethylformamide (DMF) to give 1,5-diketone has been found. It is a dimerization of ketone enolates accompanying the incorporation of one-methyl one from DMF.

The most stable conformation of denticulatolide (1), an ichthyotoxic cembranolide, obtained as a major metabolite of the soft coral, Lobophytum denticulatum, was given by molecular mechanics calculations and it was confirmed by 1H NMR measurement. The geometry of 14-membered carbocycle of 1 was found to be different from that of derivative (2) especially around the juncture part of γ-lactone. The molecular mechanics calculation successfully reproduced the conformational changes between 1 and 2.

Three labdane type diterpene glycosides ( 1 , 2 and 3 ) with 6-deoxy-L-idose have been isolated from Aster spathulifolius Maxim. and their structures have been determined on the basis of chemical and spectral data.

The structures of lobohedleolide (1) and (7Z)-lobohedleolide (2), two new cembranolides containing the α,β-unsaturated carboxylic acid system isolated from the Japanese soft coral Lobophytum hedleyi Whitelegge, were elucidated from spectral and chemical evidence, and the absolute configuration of (1) was determined by X-ray analysis of its p-bromophenacyl ester (9). Lobohedleolide (1) showed growth inhibition of the in vitro Hella cells.

The chemical constituents of the volatile oils from Chrysanthemum indicum, C. yoshinaganthum and C. cuneifolium, three botanically related tetraploid species, are described. By spectroscopic methods, 42 compounds were identified, including 22 monoterpenoids, 17 sesquiterpenoids and 3 acetylenic compounds. The sesquiterpenoids estafiatin (C. yoshinaganthum) and valeranone (C. indicum) have been found for the first time in Chrysanthemum species.

A new eunicellin-based diterpene has been isolated from a Cladiella sp. (Octocorallia, Alcyonacea). The structure and relative stereochemistry of the metabolite (1) was determined on the basis of spectroscopic and chemical evidence, and confirmed by a single-crystal X-ray structure determination.

Two new cembranoid diterpenes, cembrenene (1) and mayol (2), have been isolated from Sinularia mayi Lűttschw, along with the first reported cembrene (3) from marine organism. The structures were determined from spectral data and chemical transformations.