The absolute stereochemistry of grenadamide

Evaluating Marine Cyanobacteria as a Source for CNS Receptor Ligands

Natural products have a long history as a source of psychoactive agents and pharmacological tools for understanding the brain and its circuitry. In the last two decades, marine cyanobacteria have become a standard source of natural product ligands with cytotoxic properties. The study of cyanobacterial metabolites as CNS modulatory agents has remained largely untapped, despite the need for new molecules to treat and understand CNS disorders. We have generated a library of 301 fractions from 37 field collected cyanobacterial samples and screened these fractions against a panel of CNS receptors using radiolabeled ligand competitive-binding assays. Herein we present an analysis of the screening data collected to date, which show that cyanobacteria are prolific producers of compounds which bind to important CNS receptors, including those for 5-HT, DA, monoamine transporters, adrenergic, sigma, and cannabinoid receptors. In addition to the analysis of our screening efforts, we will also present the isolation of five compounds from the same cyanobacterial collection to illustrate how pre-fractionation followed by radioligand screening can lead to rapid identification of selective CNS agents. The systematic screening of natural products sources, specifically filamentous marine cyanobacteria, will yield a number of lead compounds for further development as pharmacological tools and therapeutics.

Cannabinomimetric Lipids: From Natural Extract to Artificial Synthesis

Endocannabinoid system is related with various physiological and cognitive processes including fertility, pregnancy, during pre- and postnatal development, pain-sensation, mood, appetite, and memory. In the latest decades, an important milestone concerning the endocannabinoid system was the discovery of the existence of the cannabinoid receptors CB1 and CB2. Anandamide was the first reported endogenous metabolite, which adjusted the release of some neurotransmitters through binding to the CB1 or CB2 receptors. Then a series of cannabinomimetric lipids were extracted from marine organisms, which possessed similar structure with anandamide. This review will provide a short account about cannabinomimetric lipids for their extraction and synthesis.

Synthesis and biological evaluation of steroidal derivatives bearing a small ring as vitamin D receptor agonists

A novel series of 3-ketolithocholic acid derivatives as well as estrone derivatives bearing a small ring for the conformational fixation of the side chain were synthesized by using a catalytic [2+2] cycloaddition and a ring-contraction rearrangement. The steroidal derivatives were evaluated for transcriptional activation of vitamin D receptor by luciferase reporter assays. Among them, two estrone derivatives showed a higher efficacy of the transactivation of vitamin D receptor than 3-ketolithocholic acid, and the small ring moieties were found to be important for the efficacy.

Marine natural products

This review covers the literature published in 2011 for marine natural products, with 870 citations (558 for the period January to December 2011) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1152 for 2011), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Enantio- and diastereocontrolled conversion of chiral epoxides to trans-cyclopropane carboxylates: application to the synthesis of cascarillic acid, grenadamide and L-(-)-CCG-II

An efficient high yielding improved method for the enantio- and diastereoselective cyclopropanation of chiral epoxides using triethylphosphonoacetate and base (Wadsworth-Emmons cyclopropanation) is reported. The utility of this protocol is illustrated by concise and practical synthesis of cascarillic acid, grenadamide and L-(-)-CCG-II, a cyclopropane containing natural products.

Lyngbyoic acid, a "tagged" fatty acid from a marine cyanobacterium, disrupts quorum sensing in Pseudomonas aeruginosa

Quorum sensing (QS) is a mechanism of bacterial gene regulation in response to increases in population density. Perhaps most studied are QS pathways mediated by acylhomoserine lactones (AHLs) in Gram-negative bacteria. Production of small molecule QS signals, their accumulation within a diffusion-limited environment and their binding to a LuxR-type receptor trigger QS-controlled gene regulatory cascades. In Pseudomonas aeruginosa, for example, binding of AHLs to their cognate receptors (LasR, RhlR) controls production of virulence factors, pigments, antibiotics and other behaviors important for its interactions with eukaryotic hosts and other bacteria. We have previously shown that marine cyanobacteria produce QS-inhibitory molecules, including 8-epi-malyngamide C (1), malyngamide C (2) and malyngolide (3). Here we isolated a new small cyclopropane-containing fatty acid, lyngbyoic acid (4), as a major metabolite of the marine cyanobacterium, Lyngbya cf. majuscula, collected at various sites in Florida. We screened 4 against four reporters based on different AHL receptors (LuxR, AhyR, TraR and LasR) and found that 4 most strongly affected LasR. We also show that 4 reduces pyocyanin and elastase (LasB) both on the protein and transcript level in wild-type P. aeruginosa, and that 4 directly inhibits LasB enzymatic activity. Conversely, dodecanoic acid (9) increased pyocyanin and LasB, demonstrating that the fused cyclopropane "tag" is functionally relevant and potentially confers resistance to β-oxidation. Global transcriptional effects of 4 in some ways replicate the gene expression changes of P. aeruginosa during chronic lung infections of cystic fibrosis patients, with reduced lasR signaling, increased biofilm and expression of the virulence locus HSI-I. Compound 4 may therefore prove to be a useful tool in the study of P. aeruginosa adaption during such chronic infections.

A new short synthesis of 10R-tuberculostearic acid and its enantiomer

Tuberculostearic acid (10R-methyloctadecanoic acid) and its 10S-enantiomer were synthesised by a chiral pool strategy, in four steps from citronellyl bromide.

Marine natural products

This review covers the literature published in 2004 for marine natural products, with 693 citations (491 for the period January to December 2004) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, coelenterates, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (716 for 2004), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies (8), and syntheses (80), including those that lead to the revision of structures or stereochemistries, have been included.

The first total synthesis of natural grenadamide

A concise, high yielding route to the naturally occurring enantiomer of grenadamide utilizing a 3,6-disubstituted 1,2-dioxine starting material is presented. The route allows for ease in synthesizing grenadamide derivatives varying at cyclopropyl carbons 2 and 3, with access to both enantiomers. Evidence for phosphorus-assisted deprotonation of 1,2-dioxines is also discussed.

A novel strategy for the asymmetric synthesis of chiral cyclopropane carboxaldehydes

A new way of combining chiral auxiliaries and substrate-directable reactions for asymmetric synthesis is described that employs a three-step sequence of aldol-cyclopropanation-retro-aldol reactions for the stereoselective synthesis of enantiopure cyclopropane carboxaldehydes.