New sesquiterpenoids from the sponge axinella cannabina

The structures of three sesquiterpenoids, axisothiocyanate-2(4), axamide-1(5) and axamide-2(6), present in the marine sponge Axinella cannabina, have been determined on the basis of chemical and spectral evidences.     

Reactions of ketenes—IX Reactions between ketene acetals and diphenylketene

Monoalkylketene acetals and monoarylketene acetals react with diphenylketene to give acylketene acetals (VII). These compounds can further react with diphenylketene to give 2,4-pyronone 4-acetals (IX), which, by mild acid hydrolysis, yields 2,4-pyronones (X).

Reaction of methylketene diethylacetal with two equivalents of diphenylketene yields 3,3-di-phenyl-5-methyl-6-diphenylmethylentetrahydropyran-2,4-dione 4-diethylacetal (XIV) in addition to small quantities of the pyronone acetal IXb.     

Isolation,Structure Determination and Synthesis of New Acetylenic Steroids from the Sponge Calyx nicaaensis

Two acetylenic steroids, cholest-5-en-23-yn-3β-ol ( 5 ) and 26,27-dinorcholest-5-en-23-yn-3β-ol ( 3 ), and another unsaturated steroidalcohol, stigmasta-5,23-dien-3β-ol ( 7 ), were isolated from the sponge Calyx nicaaensis. The structures of these two acetylenic steroids were established by synthesis. Several attempts to synthesize the marine steroids alcohol calysterol ( 1 ), with a cyclopropene-containing side chain, starting from cholest-5-en-23-yn-3β-ol are also recorded. Addition of ethyl-diazo-acetate to the triple bond was performed, but the reduction to the methyl derivative yielded decomposition products.     

Synthetic oligosaccharides as tools to demonstrate cross-reactivity between polysaccharide antigens

Escherichia coli O148 is a nonencapsulated enterotoxigenic (ETEC) Gram negative bacterium that can cause diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome in humans. The surface-exposed O-specific polysaccharide (O-SP) of the lipopolysaccharide of this bacterium is considered both a virulence factor and a protective antigen. It is built up of the linear tetrasaccharide repeating unit [3)-α-L-Rhap-(1→2)-α-D-Glcp-(1→3)-α-D-GlcNAcp-(1→3)-α-L-Rhap-(1→] differing from that of the O-SP of Shigella dysenteriae type 1 (SD) only in that the latter contains a D-Galp residue in place of the glucose moiety of the former. The close similarity of the O-SPs of these bacteria indicated a possible cross-reactivity. To answer this question we synthesized several oligosaccharide fragments of E. coli O148 O-SP, up to a dodecasaccharide, as well as their bovine serum albumin or recombinant diphtheria toxin conjugates. Immunization of mice with these conjugates induced anti-O-SP-specific serum IgG antibody responses. The antisera reacted equally well with the LPSs of both bacteria, indicating cross-reactivity between the SD and E. coli O148 O-SPs that was further supported by Western-blot and dot-blot analyses, as well as by inhibition of binding between the antisera and the O-SPs of both bacteria.     

Bromocorodienol,a diterpenoid based on a novel bicyclicskeleton from the red alga sphaerococcuscoronopifolius

The structure of bromocorodienol (3) has been determined on the basis of physical and chemical evidence and its role in the metabolic pathway of geranylgeraniol in $\text{Sphaerococcus}$$\text{coronopifolius}$ is briefly discussed.     

Power utility maximization under partial information: Some convergence results

In this paper we consider the power utility maximization problem under partial information in a continuous semimartingale setting. Investors construct their strategies using the available information, which possibly may not even include the observation of the asset prices. Resorting to stochastic filtering, the problem is transformed into an equivalent one, which is formulated in terms of observable processes. The value process, related to the equivalent optimization problem, is then characterized as the unique bounded solution of a semimartingale backward stochastic differential equation (BSDE). This yields a unified characterization for the value process related to the power and exponential utility maximization problems, the latter arising as a particular case. The convergence of the corresponding optimal strategies is obtained by means of BSDEs. Finally, we study some particular cases where the value process admits an explicit expression.     

Axisonitrile-3, axisothiocyanate-3 and axamide-3. Sesquiterpenes with a novel spiro[4,5]decane skeleton from the sponge Axinella cannabina

Axisonitrile-3 from the marine sponge Axinella cannabina has been shown, on the basis of chemical and spectral data and by single-crystal 3-dimensional X-ray diffraction study, to be 1. Axisonitrile-3 was found to be a sesquiterpene isonitrile with a novel carbon skeleton (“spiroaxane”). From the same sponge, axisothiocyanate-3 (2) and axamide-3 (3), closely related to 1, have been also isolated and their structures determined.