Hideo Iio

Chemical defence by means of extrusive cortical granules in the heterotrich ciliate Climacostomum virens

The heterotrich ciliate Climacostomum virens has colourless cortical granules morphologically similar to pigmentocysts (extrusive pigment granules) in the two coloured heterotrichs, Blepharisma japonicum and Stentor coeruleus , in which toxic pigments in pigmentocysts are used for chemical defence against predators. We examined whether cortical granules in C. virens are also defensive organelles. We showed: 1) cortical granules in C. virens are toxin-containing extrusive organelles; 2) artificially-induced cortical-granules-deficient cells in C. virens are more vulnerable than normal cells to the raptorial ciliate Dileptus margaritifer , while they are indistinguishable from intact cells in their capacity to grow; 3) cortical granules contain the colourless resorcinolic toxin climacostol, 1,3-dihydroxy-5-[(Z)-2′-nonenyl]benzene, which was recently isolated from C . virens ; and 4) chemically-synthesized climacostol induces in D. margaritifer behavioural and pathological reactions which are essentially the same with those observed in the interaction with C. virens . We conclude that cortical granules of C. virens are extrusomes (extrusive organelles in protists) for chemical defence against predators and that they carry out the defence by discharging colourless toxins including climacostol. The function of chemical defence in extrusomes of heterotrich ciliates is, therefore, independent of pigmentation.

Defence function of pigment granules in Stentor coeruleus

Pigment granules in Stentor coeruleus are extrusive organelles containing the pigment, stentorin, which provides the blue-green colouration to this ciliate. We studied the defence function of these organelles by 1) observing the interaction between S. coeruleus and the predatory ciliate Dileptus margaritifer; 2) comparing normally-pigmented cells and artificially-bleached cells of S. coeruleus as prey for the predator; and 3) measuring the toxicity of chemically-synthesized stentorin to D. margaritifer, S. coeruleus, and 7 other ciliates. When a Dileptus attacked a Stentor, the Stentor released a mass of bluish material and the Dileptus retreated. Bleached cells of S. coeruleus were more vulnerable than normally pigmented cells to the predator. Stentorin was highly toxic to D. margaritifer (LD50, 0.6—1.0 μg/ml) in the dark, but much less toxic to S. coeruleus (LD50, 90 μg/ml). Under certain conditions, Dileptus was killed by normally pigmented Stentor, but not by bleached ones. We conclude that pigment granules of S. coeruleus function as organelles of defence against D. margaritifer and that the chemical basis of this defence is the pigment stentorin.

Total synthesis of (±)-ageline a, a physiologically active constituent ofAgelas sponges

Abstract The monocyclic diterpene moiety of ageline A ( 1 ) was convergently constructed by the palladium-mediated coupling of C 9 -terpenic chain as vinyl bromide 10 and C 11 -monocyclic segment as alkylzinc compound 16 , which was obtained through a stereoselective cyclization and associated transformations. The appendage of 9-methyladenine ring to the diterpene unit led to the total synthesis of (+)-ageline A.

Remarkable stereocontrol observed in the ring formation by intramolecular hosomi-sakurai reaction

Abstract The cyclization of 2-(3′,4′-dimethyl6′-trimethylsilyl-4′-hexenyl)-2-cyclohexenone with TiCl 4 , afforded stereospecifically 6α,7α-dimethyl-6β-vinyl-5βH-1-decalone derivative and the two-fold diastereoselection involved is reasoned in terms of orientation control and folding strain control.

Climacostol, a defense toxin of the heterotrich ciliate Climacostomum virens against predators

Abstract A toxic substance (climacostol) of the protozoan ciliate Climacostomum virens against the predatory ciliate Dileptus margaritifer was established as 1,3-dihydoxy-5-[(Z)-2′-nonenyl]benzene. The structure was rigorously confirmed by the total synthesis.

One-pot stereospecific construction of cis-clerodane skeleton by means of doubly stereocontrolled cyclization: Total synthesis of linaridial

Doubly stereocontrolled cyclization of the allylsilane derivative 1 followed by trapping of the enolate with ClCH2SMe gives in one-pot manner the decalone derivatve 5 in which all of the four contiguous diastereomeric centers of cis-clerodane skeleton have been secured. The total synthesis of linaridial 4 have been accomplished from 5.

Asymmetric synthesis of clerodane diterpenoids: total synthesis of (–)-methyl kolavenate

The asymmetric synthesis of (8R,9S,10R)-4,8,9-trimethyl-9-vinyl-Δ4-3-octalone, a versatile intermediate for the syntheses of both trans- and cis-neo-clerodane diterpenoids, has been achieved by extension of Enders asymmetric alkylation, and its utility is exemplified by the total synthesis of (–)-methyl kolavenate, the first example of a clerodane diterpenoid in optically active form.

A new synthesis of α-fluorovinylsulfones utilizing the Peterson olefination methodology

Abstract α-Fluoro-α-silyl-substituted sulfones 1 are readily prepared from fluoromethyl phenyl sulfone and the appropriate silyl chloride. The use of TBSCl improves both the stability and yield of 1 . Lithium derivatives 4 undergo a smooth Peterson olefination reaction with less-enolizable carbonyl compounds to give moderate to good yields of the expected α-fluorovinylsulfones 6 , in some cases with high E -stereoselectivity. One-pot reaction with 4 generated in situ from fluoromethyl phenyl sulfone in tetrahydrofuran (THF) also proceeds smoothly, particularly with aldehydes.

Unusual reaction of 2-trimethylsilylethylidenetriarylphosphoranes (seyferth-wittig reagent) with α-methylaldehydes: a novel method for highly cram-diastereoselective addition of vinyl anion equivalent

Abstract By the reaction of α-methylaldehydes with trimethylsilylethylidenetriarylphosphoranes the introduction of vinyl group is effected in highly Cram-selective manner.

Toxic and Phototoxic Properties of the Protozoan Pigments Blepharismin and Oxyblepharismin

Abstract— The toxic and phototoxic properties of blepharismin and oxyblepharismin that were purified from the pigments of a ciliated protozoan, Blepharisma japonicum, by thin‐layer chromatography, were investigated in detail. The toxicity was tested against the ciliated protozoan Dileptus margaritifer, which is relatively sensitive to blepharismin. Although oxyblepharismin has been believed to be neither toxic nor phototoxic, it was found that oxyblepharismin is toxic in the dark and is also phototoxic. This shows that oxyblepharismin can act as a photosensitizer. The toxicity and phototoxicity of these pigments were compared with those of hypericin, which is known to be a typical, strong photosensitizer from plants. It was concluded that blepharismin and oxyblepharismin have strong intrinsic toxicities in the dark compared with hypericin, but their phototoxicities are slightly weaker than that of hypericin. This strong intrinsic toxicity supports our proposal that blepharismin acts as a defensive device against predators in the dark as well as in the light. The decrease in the defensive ability and the increase in the resistance to photokilling of Blepharisma concomitant with its color change from red to blue‐purple in response to weak illumination can be explained by the decrease in toxicity and phototoxicity of the pigment itself and by the decrease in amount of the pigment.