Morris Srebnik

Natural halogenated fatty acids: their analogues and derivatives.

A comprehensive survey has been made of all fatty acids containing halogen atoms covalently bonded to carbon and which are deemed as naturally occurring. Generally thought to be minor components produced by many different organisms, these interesting compounds now number more than 300. Recent research, especially in the marine area, indicates this number will increase in the future. Sources of halogenated fatty acids include microorganisms, algae, marine invertebrates, and higher plants and some animals. Their possible biological significance has also been discussed

Natural and synthetic small boron-containing molecules as potential inhibitors of bacterial and fungal quorum sensing.

Chemical communication is a phenomenon exhibited by many different organisms and nowadays is one of the most prominent research areas at the chemistry-microbiology interface.1–6 For more than 20 years, science has recognized the ability of different bacteria to coordinate phenotype expression using signaling substances, which is a crucial process for successful environment colonization in plants, other animal hosts, and also for human beings7–10

Natural occurrence of boron-containing compounds in plants, algae and microorganisms

Discovery of naturally-occurring boron compounds, all ionophoric polyketide macrodiolide antibiotics with a single boron atom critical for activity, established at least one biochemical role of boron. This review focuses primarily on presence and distribution of boron-containing compounds in vascular plants, marine algal species, and microorganisms.

Lipid compounds of freshwater sponges: family Spongillidae, class Demospongiae

More than 100 novel, unusual and rare fatty acids, lipids and sterols have been isolated from freshwater sponges. The structures, biogenesis, synthesis and bioactivity of some lipid compounds of freshwater sponge species are reviewed.

Boron triflouride etherate on alimina - a modified Lewis acid reagent. : An improved synthesis of cannabidiol

Abstract Boron trifluoride etherate on alumina catalyses the condensation of resorcinols an monomethyl resorcinols with several monoterpenoid allylic alcohols: in contrast to parallel reactions with boron trifluoride etherate in solution the products obtained do not undergo further cyclisations.

Synthesis and evaluation of thiazolidinedione and dioxazaborocane analogues as inhibitors of AI-2 quorum sensing in Vibrio harveyi.

Two focused libraries based on two types of compounds, that is, thiazolidinediones and dioxazaborocanes were designed. Structural resemblances can be found between thiazolidinediones and well-known furanone type quorum sensing (QS) inhibitors such as N-acylaminofuranones, and/or acyl-homoserine lactone signaling molecules, while dioxazaborocanes structurally resemble previously reported oxazaborolidine derivatives which antagonized autoinducer 2 (AI-2) binding to its receptor. Because of this, we hypothesized that these compounds could affect AI-2 QS in Vibrio harveyi. Although all compounds blocked QS, the thiazolidinediones were the most active AI-2 QS inhibitors, with EC(50) values in the low micromolar range. Their mechanism of inhibition was elucidated by measuring the effect on bioluminescence in a series of V. harveyi QS mutants and by DNA-binding assays with purified LuxR protein. The active compounds neither affected bioluminescence as such nor the production of AI-2. Instead, our results indicate that the thiazolidinediones blocked AI-2 QS in V. harveyi by decreasing the DNA-binding ability of LuxR. In addition, several dioxazaborocanes were found to block AI-2 QS by targeting LuxPQ.

Control of hydroboration of 1-alkynylphosphonates, followed by Suzuki coupling provides regio- and stereospecific synthesis of di-substituted 1-alkenylphosphonates

Abstract Hydroboration of 1-alkynylphosphonates can be controlled to place boron on either C1 or C2 of the triple bond by control of reaction conditions. Initial hydroboration occurs on C1 (kinetic product), which can be isomerized to place boron on C2 (thermodynamic product) by extended heating or by use of large amounts of catalyst. Suzuki reaction of the hydroboration products with aryliodides provides a regio- and stereospecific route to disubstituted vinylphosphonates

Recent Advances in the Medicinal Chemistry of α-Aminoboronic Acids, Amine-Carboxyboranes and Their Derivatives

This article describes recent developments in the synthesis and biological activity of alpha-aminoboronic acids, amine-carboxyboranes and their derivatives as potential therapeutic agents. alpha-Amino acid analogues are of considerable interest as inhibitors of enzymes involved in amino acid and peptide metabolism. In particular, alpha-amino alkylphosphonic acids and alpha-amino alkylboronic acids, in which the carboxyl group of amino acids is replaced by a phosphonic acid or boronic acid function, respectively, constitute a unique class of amino acid mimics from which a number of potent enzyme inhibitors have been synthesized. The inhibitory activity mainly stems from the fact that the tetrahedral phosphonic moiety or the tetrahedral adduct of electrophilic boronic acid is a good mimic of the putative tetrahedral transition state or intermediate encountered in the enzymatic hydrolysis or formation of peptides. Since the peptide hydrolysis and formation invariably involves the tetrahedral high energy species in the course of the reaction, these amino acid mimics serve as a general key element for inhibitors of a broad spectrum of proteases and peptide ligases. Serine protease inhibitors provide promising compounds having a P site binding moiety and a boronic acid chelating moiety. The compounds have been shown to have high inhibitory activity.

Novel addition reactions of titanacycle phosphonates by tuning of Ti(O-i-Pr)4/2i-PrMgClElectronic supplementary information (ESI): further experimental details. See http://www.rsc.org/suppdata/cc/b2/b209149f/

Di- or tri-substituted vinylphosphonates, 2-5, can be obtained in a highly regio- and stereoselective manner from 1-alkynylphosphonates, by manipulation of Ti(O-i-Pr)4/2i-PrMgCl.

The Metastatic Stage-dependent Mucosal Expression of Sialic Acid is a Potential Marker for Targeting Colon Cancer with Cationic Polymers

PurposeLocoregional recurrence is the most common complication after adenocarcinoma resection in the colon, despite adjuvant chemotherapy. Therapy efficacy could be improved if designed to target malignant cells by incorporating specific recognition factors in the drugs or the drug vehicles. The aim of this study was to elucidate whether the overexpression of sialic acid (SA) on colonic malignant tissues could be utilized for drug targeting by cationic polymers.Materials and MethodsCell lines (IEC-6, SW-480 and SW-620) and colon polyps and normal adjacent tissues harvested from dimethylhydrazine (DMH) induced rats were used as in vitro and in vivo models of different metastatic stages of colon cancer. SA expression was identified by fluorescent wheat germ agglutinin (WGA), and verified by pretreatment with neuraminidase. The role of mucus in the mucosal binding experiments was explored by pretreatment with dithiothreitol (DTT). The binding of FITC labeled cationic polymers of various degrees of cationization to normal and malignant colonic cells and tissue was measured.ResultsSA was overexpressed on malignant colonic cells and tissues, and its expression correlated to the metastatic stage in vitro. The binding of the cationic copolymers to the cell lines and tissues correlated with the charge density of the polymer and with the metastatic stage of the cell line. The interaction between the malignant colonic cells and tissues with the polymers was SA dependent and increased after mucus removal.ConclusionCationic polymers could be used as a targeting tool to colonic malignant epithelium, to be implemented in drug delivery and diagnosis.