Biomolecular-chemical screening: a novel screening approach for the discovery of biologically active secondary metabolites. III. New DNA-binding metabolites

Electroreductive Olefin-Ketone Coupling

A user-friendly approach is presented to sidestep the venerable Grignard addition to unactivated ketones to access tertiary alcohols by reversing the polarity of the disconnection. In this work a ketone instead acts as a nucleophile when adding to simple unactivated olefins to accomplish the same overall transformation. The scope of this coupling is broad as enabled using an electrochemical approach, and the reaction is scalable, chemoselective, and requires no precaution to exclude air or water. Multiple applications demonstrate the simplifying nature of the reaction on multistep synthesis, and mechanistic studies point to an intuitive mechanism reminiscent of other chemical reductants such as SmI₂ (which cannot accomplish the same reaction).

Cyclic enaminones. Part II: applications as versatile intermediates in alkaloid synthesis

Among many other strategies, the enaminone approach is an important strategy to construct and diversify the azacyclic core in various alkaloids syntheses. In this brief review we discuss the application of cyclic enaminones as building blocks, as well as potential intermediates in the total synthesis of selected alkaloids.

Chromophenazines from the terrestrial Streptomyces sp. Ank 315

The new chromophenazines A-F [9-methyl-5-(3'-methylbut-2'-enyl)-5H-benzo[a]phenazin-7-one (1a), 9-methyl-5-(3'-methylbut-2'-enyl)-7-oxo-5,7-dihydrobenzo[a]phenazine-1-carboxylic acid (1b), 5-(3'-methylbut-2'-enyl)-7-oxo-5,7-dihydrophenazine-1-carboxamide (2), 3-benzoyl-5-(3'-methylbut-2'-enyl)-5,10-dihydrophenazine-1-carboxylic acid (5a), 3,7-dibenzoyl-5-(3'-methylbut-2'-enyl)-5,10-dihydrophenazine-1-carboxylic acid (5b), and 3,7-dibenzoyl-5-(3'-methylbut-2'-enyl)-5,10-dihydrophenazine-1-carboxamide (5c)], together with phenazine-1-carboxylic acid, 1-phenazinecarboxamide, 1-phenazinol, tryptophol, and anthranilic acid, were isolated from Streptomyces sp. Ank 315. The structures of the new compounds were established on the basis of spectroscopic data, 1D NOE, 2D NMR, and ESIMS measurements and comparison with literature values.

Antimicrobial natural products: an update on future antibiotic drug candidates

Over the last decade, it has become clear that antimicrobial drugs are losing their effectiveness due to the evolution of pathogen resistance. There is therefore a continuing need to search for new antibiotics, especially as new drugs only rarely reach the market. Natural products are both fundamental sources of new chemical diversity and integral components of today's pharmaceutical compendium, and the aim of this review is to explore and highlight the diverse natural products that have potential to lead to more effective and less toxic antimicrobial drugs. Although more than 300 natural metabolites with antimicrobial activity have been reported in the period 2000-2008, this review will describe only those with potentially useful antimicrobial activity, viz. with MICs in the range 0.02-10 microg mL(-1). A total of 145 compounds from 13 structural classes are discussed, and over 100 references are cited.

2070-DTI, A Topoisomerase Inhibitor Produced byStreptomycessp. Strain No. 2070

A novel inhibitor of topoisomerase II designated as 2070-DTI was isolated from the culture filtrate of Streptomyces sp. strain No. 2070. The structure was determined to be that of the known soyasaponin I on the basis of spectroscopic methods (NMR and MS). 2070-DTI strongly inhibited the decatenation activity of human placenta topoisomerase II in a noncompetitive manner, and weakly inhibited or was inert towards the relaxation activities of various topoisomerase I's and DNA-related enzymes. 2070-DTI is an inhibitor belonging to the cleavable complex-nonforming type without DNA intercalation.

Development of a solid-phase ‘asymmetric resin-capture–release’ process: application of an ephedrine chiral resin in an approach to γ-butyrolactones

The potential of a solid-phase asymmetric resin-capture-release strategy for high-throughput synthesis has been evaluated. Fukuzawa's Sm(ii)-mediated, asymmetric approach to gamma-butyrolactones was selected to illustrate the feasibility of such a process. Alpha,beta-unsaturated esters immobilised on an ephedrine chiral resin have been applied in an asymmetric approach to gamma-butyrolactones. Lactone products are obtained in moderate isolated yields with selectivities up to 96% ee. In addition, we have shown that the ephedrine resin can be conveniently recovered and recycled although in some cases lower yields were obtained on reuse of the chiral resin. A short synthesis of a moderate DNA-binding microbial metabolite using asymmetric resin-capture-release is also described.

Application of an ephedrine chiral linker in a solid-phase, 'asymmetric catch-release' approach to gamma-butyrolactones

A Sm(II)-mediated, asymmetric, intermolecular ketyl-olefin addition employing alpha,beta-unsaturated esters linked to resin through an ephedrine 'chiral link' has been applied in a direct 'asymmetric catch-release' approach to gamma-butyrolactones.