Concetta Imperatore

A mild and easy one-pot procedure for the synthesis of 2-deoxysugars from glycals

Abstract Glycals can be converted into the corresponding 2-deoxysugars in good yields by treatment with N-iodosuccinimide in CH3CN–H2O 95:5 and removal of the iodide group using Na2S2O4 in DMF/H2O at room temperature. This method is easy to apply, sufficiently mild to allow the survival of acid-sensitive groups such as silyl and trityl ethers and less harmful to the environment than metal-based reactions.

Meroterpenes from Marine Invertebrates: Structures, Occurrence, and Ecological Implications

Meroterpenes are widely distributed among marine organisms; they are particularly abundant within brown algae, but other important sources include microorganisms and invertebrates. In the present review the structures and bioactivities of meroterpenes from marine invertebrates, mainly sponges and tunicates, are summarized. More than 300 molecules, often complex and with unique skeletons originating from intra- and inter-molecular cyclizations, and/or rearrangements, are illustrated. The reported syntheses are mentioned. The issue of a potential microbial link to their biosynthesis is also shortly outlined.

Immunomodulating glycosphingolipids: an efficient synthesis of a 2′-deoxy-α-galactosyl-GSL

Abstract A new and efficient approach to the total synthesis of 2′-deoxy-α-galactosyl glycosphingolipids was accomplished. Commercially available 3,4,6-tri- O -acetylgalactal was used as the chiral starting material for both the sugar and phytosphingosine building blocks required for the synthesis of 1- O -(2-deoxy-α- d -galactopyranosyl)-2-docosanoylamino-1,3,4-octadecanetriol. The key step of the synthetic strategy was the stereoselective α-glycosidation of the azido precursor of sphingosine.

A biosynthetically significant new bacteriohopanoid present in large amounts in the Caribbean sponge Plakortis simplex

Abstract In addition to the previously reported bacteriohopanoids, the marine sponge Plakortis simplex was shown to contain large amounts of (32R,33S,34S)-32,35-anhydrobacteriohopanetetrol. The structure of this new bacteriohopanoid was determined by extensive NMR analysis, and further supports the hypothesized biosynthetic pathway to bacteriohopanoids. Altogether, the amounts of bacteriohopanoids in P. simplex is as high as 50% of sterols in weight, and these compounds could play a structural role in the sponge cell membranes.

Alkaloids from Marine Ascidians

About 300 alkaloid structures isolated from marine ascidians are discussed in term of their occurrence, structural type and reported pharmacological activity. Some major groups (e.g., the lamellarins and the ecteinascidins) are discussed in detail, highlighting their potential as therapeutic agents for the treatment of cancer or viral infections.

Glycolipids from Sponges. 20.(1) J-Coupling Analysis for Stereochemical Assignments in Furanosides: Structure Elucidation of Vesparioside B, a Glycosphingolipid from the Marine Sponge Spheciospongia vesparia

Reinvestigation of the glycosphingolipid composition of the marine sponge Spheciospongia vesparia revealed the presence of vesparioside B ( 2a), a new furanose-rich hexaglycosylated glycosphingolipid that is the most complex glycosphingolipid isolated from a marine sponge to date. The structure of the new compound was elucidated using extensive 2D NMR studies and chemical degradation. Particularly useful for structure elucidation of vesparioside B was a quantum mechanical computational study, showing that in furanosides a vicinal coupling constant <2.0 Hz (for H-1/H-2 or H-3/H-4) or <3.5 Hz (for H-2/H-3) is a proof of the trans orientation of the relevant protons. This general rule, combined with ROE data, allowed us to elucidate the relative stereochemistry (including anomeric configuration) of the three furanose five-membered rings.

Alkaloids from Marine Invertebrates as Important Leads for Anticancer Drugs Discovery and Development

The present review describes research on novel natural antitumor alkaloids isolated from marine invertebrates. The structure, origin, and confirmed cytotoxic activity of more than 130 novel alkaloids belonging to several structural families (indoles, pyrroles, pyrazines, quinolines, and pyridoacridines), together with some of their synthetic analogs, are illustrated. Recent discoveries concerning the current state of the potential and/or development of some of them as new drugs, as well as the current knowledge regarding their modes of action, are also summarized. A special emphasis is given to the role of marine invertebrate alkaloids as an important source of leads for anticancer drug discovery.

The new carotenoid pigment moraxanthin is associated with toxic microalgae.

The new pigment “moraxanthin” was found in natural samples from a fish mortality site in the Inland Bays of Delaware, USA. Pure cultures of the species, tentatively named Chattonella cf. verruculosa, and natural samples contained this pigment as a dominant carotenoid. The pigment, obtained from a 10 L culture of C. cf. verruculosa, was isolated and harvested by HPLC and its structure determined from MS and 1D- and 2D-NMR. The data identified this pigment as a new acylated form of vaucheriaxanthin called moraxanthin after the berry like algal cell. Its presence in pure cultures and in natural bloom samples indicates that moraxanthin is specific to C. cf. verruculosa and can be used as a marker of its presence when HPLC is used to analyze natural blooms samples.

The First 12-Methylhopanoid: 12-Methylbacteriohopanetetrol from the Marine Sponge Plakortis simplex

Abstract Large amounts of bacteriohopanoids have been isolated from the marine sponge Plakortis simplex . In addition to the common bacteriohopanetetrol, the new 12-methylbacteriohopanetetrol, with an unprecedented methylation at C-12, was isolated and characterized by an extensive NMR analysis. While bacteriohopanetetrol is most likely of dietary origin, the unusual methylation at C-12 could be carried out by the sponge.

Plaxyloside from the Marine Sponge Plakortis simplex: an Improved Strategy for NMR Structural Studies of Carbohydrate Chains

Plaxyloside, a glycolipid composed of a C35 linear polyisoprenoid alcohol aglycone and a linear carbohydrate chain made up of six β-xylopyranose units, has been isolated as its peracetate from the Caribbean sponge Plakortis simplex, and its structure determined on the basis of spectral and chemical data. Study of plaxyloside showed that: (a) carbohydrate chains with repetitive structures can be conveniently studied as their peracetates by NMR spectroscopy in C6D6, thanks to the peculiar conformational behavior of these derivatives, and (b) coupling constant analysis can be used to establish relative configurations in pyranose sugars even in the presence of conformational equilibria.