Total Synthesis and Stereochemical Revision of Biemamides B and D

Gauge Dependence of the S̃ Molecular Orbital Space Decomposition of Optical Rotation

The measurement of optical rotation (OR) is a foundational technique for the detection and characterization of chiral molecules, but it is poorly understood how the observed property relates to the structure of the molecule. Over the years, several schemes have been developed to decompose the OR into more chemically intuitive contributions. In this paper, we introduce two alternative formulations of our previously developed S̃ molecular orbital space decomposition. These new expressions use the modified velocity gauge-magnetic (MVG-M) and -electric (MVG-E) definitions of OR, rather than the length gauge-magnetic (LG-M) definition used in the original paper. Comparing these formulations across a small set of previously studied chiral molecules, we find that these different definitions produce consistent physical interpretations of the OR. These results demonstrate that the S̃ methodology for investigations of structure-property relationships in chiral molecules is insensitive to the choice of gauge.

Synthetic Applications of Aziridinium Ions

Nonactivated aziridine with an electron-donating group at the ring nitrogen should be activated to an aziridinium ion prior to being converted to cyclic and acyclic nitrogen-containing molecules. This review describes ways to generate aziridinium ions and their utilization for synthetic purposes. Specifically, the intra- and intermolecular formation of aziridinium ions with proper electrophiles are classified, and their regio- and stereoselective transformations with nucleophiles are described on the basis of recent developments.

Marine natural products

This review covers the literature published in 2019 for marine natural products (MNPs), with 719 citations (701 for the period January to December 2019) 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 (1490 in 440 papers for 2019), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Methods used to study marine fungi and their chemical diversity have also been discussed.

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.