https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

Relationships between the carbon-oxygen stretching frequencies of carboxylato complexes and the type of carboxylate coordination

Life on earth is almost entirely solar-powered. We can get some idea of the enormous quantity of energy received from the sun by noting that during daylight hours, the sun provides several thousand times more power to the surface of the U.S.A. than is produced by all of the nation’s electrical power stations. 1,2 Around 50% of the radiation that reaches the earth’s surface, roughly the visible region, is of a frequency useful to photosynthetic organisms. Oxygenic photosynthetic organisms convert this radiation into chemical energy, in the form of carbohydrate and dioxygen, at an optimal efficiency of something like 25%. 3 These products together sustain the rest of aerobic life, with carbohydrate acting as a source of high-energy electrons and dioxygen providing a lower-energy destination for these electrons. The overall equation of oxygenic photosynthesis is given in eq 1, where (CH2O) represents carbohydrate:

Water-splitting chemistry of photosystem II.

The nature of the bonding in transition-metal compounds.

A rotationally hindered and thus stereogenic biaryl axis is the structurally and stereochemically decisive element of a steadily growing number of natural products, chiral auxiliaries, and catalysts. Thus, it is not surprising that significant advances have been made in the asymmetric synthesis of axially chiral biaryl compounds over the past decade. In addition to the classic approach (direct stereoselective aryl-aryl coupling), innovative concepts have been developed in which the asymmetric information is introduced into a preformed, but achiral-that is, symmetric or configurationally labile-biaryl compound, or in which an aryl--C single bond is stereoselectively transformed into an axis. This Review classifies these strategies according to their underlying concepts and critically evaluates their scope and limitations with reference to selected model reactions and applications. Furthermore, the preconditions required for the existence of axial chirality in biaryl compounds are discussed.

Atroposelective Synthesis of Axially Chiral Biaryl Compounds

The first crystal structure of a drug (daunomycin) bound to a parallel-stranded intermolecular telomeric G4 quadruplex (d(TGGGGT)4) has been determined to high resolution. A planar assemblage of three daunomycin molecules stacks onto the 5' end of the G4 column, with the daunosamine substituents occupying three of the four quadruplex grooves. The surface area of the terminal G-quartet in this parallel DNA quadruplex, presently occupied by three daunomycins, is sufficiently large that it could easily accommodate other potential telomerase inhibitors such as substituted porphyrins or telomestatin.

Structure of the first parallel DNA quadruplex-drug complex.

A Method for Driving O-Atom Transfer: Secondary Ion Binding to a Tetraamide Macrocyclic Ligand

The paper describes the synthesis of a crystalline osmium complex (Os(eta/sup 2/ -CH/sub 2/O) (CO)/sub 2/(PPh/sub 3/)/sub 2/) in which formaldehyde functions as a dihapto ligand. IR and /sup 1/HNMR spectral data are reported. X-ray crystal determination confirmed the mononuclear formulation of the inner coordination sphere. Heating the crystalline complex at 75/sup 0/C for several hours produced the formyl-hydrido complex, Os(CHO)H-(CO)/sub 2/(PPh/sub 3/)/sub 2/: solutions of this complex were found to be unstable above 40/sup 0/C, eliminating hydrogen and forming Os(CO)/sub 3/(PPh/sub 3/)/sub 2/. The formaldehyde complex reacts with hydrochloric acid to yield Os(CH/sub 2/Cl) (CO)/sub 2/(PPh/sub 3/)/sub 2/. With 1 equiv of trifluoracetic acid a compound with spectral properties appropriate for the hydroxymethyl species is obtained, but this product could not be isolated. Methylation with methyl trifluoromethane--sulfonate produces (Os(CH/sub 2/OMe) (H/sub 2/O) (CO)/sub 2/(PPh/sub 3/)/sub 2/)CF/sub 3/SO/sub 3/.

Organometallic models for possible Fischer-Tropsch intermediates. Synthesis, structure, and reactions of a formaldehyde complex of osmium

An osmium-carbyne complex

Stepwise Reactions of Acetylenes with Iridium Thiocarbonyl Complexes To Produce Isolable Iridacyclobutadienes and Conversion of These to either Cyclopentadienyliridium or Tethered Iridabenzene Complexes

George R. Clark

Papers

Structure of the first parallel DNA quadruplex-drug complex.

A Method for Driving O-Atom Transfer: Secondary Ion Binding to a Tetraamide Macrocyclic Ligand

Organometallic models for possible Fischer-Tropsch intermediates. Synthesis, structure, and reactions of a formaldehyde complex of osmium

An osmium-carbyne complex

Stepwise Reactions of Acetylenes with Iridium Thiocarbonyl Complexes To Produce Isolable Iridacyclobutadienes and Conversion of These to either Cyclopentadienyliridium or Tethered Iridabenzene Complexes