Investigation of tetrasubstituted heterocycles reveals hydantoins as a promising scaffold for development of novel antimicrobials with membranolytic properties

Mimics of antimicrobial peptides (AMPs) have been proposed as a promising class of antimicrobial agents. We report the analysis of five tetrasubstituted, cationic, amphipathic heterocycles as potential AMP mimics. The analysis showed that the heterocyclic scaffold had a strong influence on the haemolytic activity of the compounds, and the hydantoin scaffold was identified as a promising template for drug lead development. Subsequently, a total of 20 hydantoin derivatives were studied for their antimicrobial potency and haemolytic activity. We found 19 of these derivatives to have very low haemolytic toxicity and identified three lead structures, 2dA, 6cG, and 6dG with very promising broad-spectrum antimicrobial activity. Lead structure 6dG displayed minimum inhibitory concentration (MIC) values as low as 1 μg/mL against Gram-positive bacteria and 4-16 μg/mL against Gram-negative bacteria. Initial mode of action (MoA) studies performed on the amine derivative 6cG, utilizing a luciferase-based biosensor assay, suggested a strong membrane disrupting effect on the outer and inner membrane of Escherichia coli. Our findings show that the physical properties and structural arrangement induced by the heterocyclic scaffolds are important factors in the design of AMP mimics.

Recent approaches towards one-carbon homologation-functionalization of aldehydes

One-carbon homologation-functionalization in organic synthesis is a quite challenging and difficult task in terms of atom economy, ease of reaction, selectivity and number of steps involved. Due to the reactivity associated with most classes of carbonyls, these groups have always attracted a great deal of attention from synthetic chemists to transform them into various functionalities. In this context various researchers developed new methods for one-carbon extension-functionalization of carbonyls that serve as effective synthetic methodologies and are widely used in target-oriented and natural product synthesis. On account of the vast applicability associated with these transformations, herein we seek to summarize and highlight the important synthetic achievements in this advancing arena for various one-carbon homologation cum functionalization reactions of aldehydes and deep dive into some modern approaches adopted by organic chemists.

Synthesis of Sterically Fixed Phytochrome Chromophore Derivatives Bearing a 15 E- Fixed or 15 E- Anti- Fixed CD-Ring Component

To analyze the structure and function of phytochrome chromophores, we have been synthesizing natural and unnatural bilin chromophores of phytochromes. In this manuscript, we report the synthesis of sterically fixed 15 E- fixed 18Et-biliverdin (BV) and 15 E- anti-fixed 18Et-BV derivatives. The key reaction is the introduction of an sp³ carbon alkyl chain bearing a leaving group at the meso-position of the CD-ring component by using the corresponding Grignard reagents in the presence of LiCl.