Palytoxin (1, C129H223N3054, Figure 1) is one of the most potent and complex marine toxins.' Though first isolated from the zoanthid Palythoa toxica, its biogenetic origin was questioned because of marked seasonal and regional variations,2 but the question was never pursued. Sporadic occurrence of palytoxin in an alga,3 crabs," and a herbivorous fish5 also suggested that the toxin might be produced by a microorganism and transmitted to the marine food chain, as is the case with ciguatera, where the epiphytic dinoflagellate Gambierdiscus toxicus produces ciguatoxins and maitotoxin that are isolated from fish.6 Ostreopsis siamensis drew our attention because of its close taxonomical relationship to G. toxicus and the potency of its toxins, named ostre~cins.~ In this Communication, we report the major ostreocin as a palytoxin analog. 0. siamensis (SOA1 strain) was collected at Aka Island, Okinawa, Japan, and grown for 30 days under the same culture conditions as G. toxic~s.'~ Cells harvested by filtration were extracted three times with MeOWH20 (1 : 1) at room temperature and then with MeOH/H20/HOAc (50:50:0.2) under reflux. Purification of ostreocins from the combined extracts was carried out by solvent partition and column chromatography.8 Ostreocins were resolved into five constituents. Purification was monitored by mouse assay following characteristic W maxima. The major constituent, ostreocin D, accounted for 70% of total toxicity. From 936 L of culture, 3.8 mg of ostreocin D was recovered. (2) Moore, R. E.; Helfrich, P.; Patterson, G. M. L. Oceanus 1982, 25, 54-62. (3) Maeda, M.; Kodama, R.; Tanaka, T.; Yoshizumi, H.; Nomoto, K.; Takemoto, T.; Fujita, M. 27th Symposium on the Chemistry of Natural Products; Tanaka, O., Ed.; Symposium papers, Hiroshima, Japan, 1985; Yamawaki Publishing: Hiroshima, 1985; pp 616-623. (4) (a) Yasumoto, T.; Yasumura, D.; Ohizumi, Y.; Takahashi, M.; Alcala, A. C.; Alcala, L. C.(8) The algal extracts were suspended in CHzCl2 and extracted with MeOWH20 (1:l). The aqueous phase, after being concentrated, was extracted with 1-BuOH. The 1-BuOH extract was successively chromatographed on the following columns with solvents as indicated: Toyopearl HW60-fine, MeOWH20 (3:2), Inertsil C8, H20, H20iPrOH (4:1,3:Z); CM Toyopearl 650M. 1% HOAC. The eluates were monitored by mouse assay. Resolution of ostreocins into five constituents and final purification of ostreocin D were achieved on Develosil TMS-5 with H20/CH3CN (3: 1) containing 0.1% HOAc. Eluates were monitored with a Hitachi C-6500 J3D Chromatosystem at 235 and 263 nm. All columns were washed with 10 mM aqueous EDTA-2Na before use. 47, 1029-1033. 0002-7863/95/15 17-5389$09.00/0 on Figure 1. Planar structure of palytoxin (1) and ostreocin D (3,26bisdesmethyldeoxypalytoxin). Bold lines denote connectivities elucidated by DQF-COSY, TOCSY, HSQC, and HMBC data. W chromophores are bracketed.12 Palytoxin, Rl = RZ = Me. Ostreocin D, R1 = Rz = H; O H -H (position not located). Ostreocin D (OST-D) was a colorless amorphous solid: positive to ninhyd...

(+)-Catechin and (-)-epicatechin are known to be biologically effective antioxidants present in the human diet, particularly in wine and tea. We studied the metabolism of these compounds to elucidate the truly active structures in biological fluids by their oral administration to rats. Without any treatment with beta-glucuronidase and sulfatase, a pair of metabolites were detected at much higher concentrations in the plasma, bile, and urine than the originally ingested compounds. Each major metabolite found in the plasma at the highest concentration was excreted in both the bile and urine, and was purified from urine. Their chemical structures were established to be (+)-catechin 5-O-beta-glucuronide and (-)-epicatechin 5-O-beta-glucuronide by MS and NMR analyses. These glucuronide conjugates exhibited high antioxidative activities as superoxide anion radical scavengers like their parent compounds. It is concluded that (+)-catechin 5-O-beta-glucuronide and (-)-epicatechin 5-O-beta-glucuronide are the biologically active in vivo structures of the ingested polyphenolic antioxidants.

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All eight possible A-ring diastereomers of 2-methyl-1, 25-dihydroxyvitamin D(3) (2) and 2-methyl-20-epi-1, 25-dihydroxyvitamin D(3) (3) were convergently synthesized. The A-ring enyne synthons 19 were synthesized starting with methyl (S)-(+)- or (R)-(-)-3-hydroxy-2-methylpropionate (8). This was converted to the alcohol 14 as a 1:1 epimeric mixture in several steps. After having been separated by column chromatography, each isomer led to the requisite A-ring enyne synthons 19 again as 1:1 mixtures at C-1. Coupling of the resulting A-ring enynes 20a-h with the CD-ring portions 5a,b in the presence of a Pd catalyst afforded the 2-methyl analogues 2a-h and 3a-h in good yield. In this way, all possible A-ring diastereomers were synthesized. The synthesized analogues were biologically evaluated both in vitro and in vivo. The potency was highly dependent on the stereochemistry of each isomer. In particular, the alpha alpha beta-isomer 2g exhibited 4-fold higher potency than 1 alpha,25-dihydroxyvitamin D(3) (1) both in bovine thymus VDR binding and in elevation of rat serum calcium concentration and was twice as potent as the parent compound in HL-60 cell differentiation. Furthermore, its 20-epimer, that is, 20-epi-alpha alpha beta 3g, exhibited exceptionally high activities: 12-fold higher in VDR binding affinity, 7-fold higher in calcium mobilization, and 590-fold higher in HL-60 cell differentiation, as compared to 1 alpha,25-dihydroxyvitamin D(3) (1). Accordingly, the double modification of 2-methyl substitution and 20-epimerization resulted in unique activity profiles. Conformational analysis of the A-ring by (1)H NMR and an X-ray crystallographic analysis of the alpha alpha beta-isomer 2g are also described.

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Two new malyngamides, M and N (1, 2), were isolated along with malyngamide I acetate (3) from the Hawaiian red alga Gracilaria coronopifolia. Our results suggest that malyngamide N (2) is a revised structure of deacetoxystylocheilamide (5). The absolute configuration of malyngamide I acetate was deduced to be 3 using the reversed octant rule.

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Alchivemycin A, a novel polycyclic polyketide, was isolated from the culture extract of a plant-derived actinomycete Streptomyces sp. The structure and relative configuration were elucidated by spectroscopic analysis and X-ray crystallography, and the absolute configuration was determined by a (1)H NMR anisotropy method using MPA ester derivatization. The new compound contains an unprecedented heterocyclic ring system, 2H-tetrahydro-4,6-dioxo-1,2-oxazine. Alchivemycin A showed potent antimicrobial activity against Micrococcus luteus and inhibitory effects on tumor cell invasion.