Synthesis and biological evaluation of a MraY selective analogue of tunicamycins

Synthesis of chimera oligopeptide including furanoid β-sugar amino acid derivatives with free OHs: mild but successful removal of the 1,2-O-isopropylidene from the building block

Complementary to hydrophobic five membered ring β-amino acids (e.g. ACPC), β-sugar amino acids (β-SAAs) have found increasing application as hydrophilic building blocks of foldamers and α/β chimeric peptides. Fmoc-protected β-SAAs [e.g. Fmoc-RibAFU(ip)-OH] are indeed useful Lego elements, ready to use for SPPS. The removal of 1,2-OH isopropylidene protecting group increasing the hydrophilicity of such SAA is presented here. We first used N3-RibAFU(ip)-OH model compound to optimize mild deprotection conditions. The formation of the 1,2-OH free product N3-RibAFU-OH and its methyl glycoside methyl ester, N3-RibAFU(Me)-OMe were monitored by RP-HPLC and found that either 50% TFA or 8 eqv. Amberlite IR-120 H+ resin in MeOH are optimal reagents for the effective deprotection. These conditions were then successfully applied for the synthesis of chimeric oligopeptide: -GG-X-GG- [X=RibAFU(ip)]. We found the established conditions to be effective and-at the same time-sufficiently mild to remove 1,2-O-isopropylidene protection and thus, it is proposed to be used in the synthesis of oligo- and polypeptides of complex sequence combination.

Uridine natural products: Challenging targets and inspiration for novel small molecule inhibitors

Nucleoside derivatives, in particular those featuring uridine, are familiar components of the nucleoside family of bioactive natural products. The structural complexity and biological activities of these compounds have inspired research from organic chemistry and chemical biology communities seeking to develop novel approaches to assemble the challenging molecular targets, to gain inspiration for enzyme inhibitor development and to fuel antibiotic discovery efforts. This review will present recent case studies describing the total synthesis and biosynthesis of uridine natural products, and de novo synthetic efforts exploiting features of the natural products to produce simplified scaffolds. This research has culminated in the development of complementary strategies that can lead to effective uridine-based inhibitors and antibiotics. The strengths and challenges of the juxtaposing methods will be illustrated by examining select uridine natural products. Moreover, structure-activity relationships (SAR) for each natural product-inspired scaffold will be discussed, highlighting the impact on inhibitor development, with the aim of future uridine-based small molecule expansion.