Pd‐Catalyzed Carboamination of Alkylidenecyclopropanes: Synthesis of Congested Pyrrolidines and Piperidines

The synthesis of densely functionalized N‐heterocycles is an ongoing challenge in chemical synthesis. Herein, we report an efficient method for the construction of pyrrolidine and piperidine scaffolds using a palladium‐catalyzed carboamination of alkylidenecyclopropanes.     

An expedient synthesis of orthogonally protected lysinoalanine from Aloc-protected Garner’s aldehyde

An expedient synthesis of orthogonally protected lysinoalanine has been developed. We have prepared a novel Garner’s aldehyde derivative bearing an Aloc group; reductive amination of this aldehyde with Fmoc-Lys-OPMB gave the lysinoalanine skeleton. This was then transformed into an orthogonally protected lysinoalanine derivative suitable for the synthesis of side-chain bridged cyclic peptides by solid phase peptide synthesis methods.     

Chemical Synthesis of the Major Constituents of Salmonella Minnesota Monophosphoryl Lipid A

Abstract

Structural investigations have shown that lipid A constitutes the active principle of lipopoly saccharide (LPS, endotoxin), a complex amphipathic molecule located on the cell surface of Gram-negative bacteria.¹ Lipid A elicits not only the typical endotoxic reactions such as fever and lethal shock but also adjuvant, antitumor and other beneficial effects.¹ As a result, there has been a great deal of interest in the synthesis of lipid A derivatives possessing low toxicity.^1,2     

Combined Photoredox and Carbene Catalysis for the Synthesis of Ketones from Carboxylic Acids**

As a key element in the construction of complex organic scaffolds, the formation of C−C bonds remains a challenge in the field of synthetic organic chemistry. Recent advancements in single-electron chemistry have enabled new methods for the formation of various C−C bonds. Disclosed herein is the development of a novel single-electron reduction of acyl azoliums for the formation of ketones from carboxylic acids. Facile construction of the acyl azolium in situ followed by a radical–radical coupling was made possible merging N-heterocyclic carbene (NHC) and photoredox catalysis. The utility of this protocol in synthesis was showcased in the late-stage functionalization of a variety of pharmaceutical compounds. Preliminary investigations using chiral NHCs demonstrate that enantioselectivity can be achieved, showcasing the advantages of this protocol over alternative methodologies.     

Copolymerization of Metal Nanoparticles: A Route to Colloidal Plasmonic Copolymers

The resemblance between colloidal and molecular polymerization reactions is very useful in fundamental studies of polymerization reactions, as well as in the development of new nanoscale systems with desired properties. Future applications of colloidal polymers will require nanoparticle ensembles with a high degree of complexity that can be realized by hetero‐assembly of NPs with different dimensions, shapes, and compositions. A method has been developed to apply strategies from molecular copolymerization to the co‐assembly of gold nanorods with different dimensions into random and block copolymer structures (plasmonic copolymers). The approach was extended to the co‐assembly of random copolymers of gold and palladium nanorods. A kinetic model validated and further expanded the kinetic theories developed for molecular copolymerization reactions.     

Psychological and Physiological Mechanisms By Which Discovery and Didactic Methods Work

Since ancient times, educators and parents have pondered which of two basic instructional strategies is more effective. This article describes physiological, affective, and cognitive mechanisms by which didactic and discovery methods appear to work, as revealed by a search of the research literature of the past decade or so. The optimal instructional method depends on the instructional objective, the educator's skills, and the nature of the students. But given the predominance of didactic method in today's schools–and the large body of research suggesting significant advantages to the discovery methods–more use of discovery methods should probably be employed, especially for students for whom didactic methods appear to be sub-optimal.