The role of protein dynamics in the reaction catalyzed by dihydrofolate reductase from the hyperthermophile Thermotoga maritima (TmDHFR) has been examined by enzyme isotope substitution ((15)N, (13)C, (2)H). In contrast to all other enzyme reactions investigated previously, including DHFR from Escherichia coli (EcDHFR), for which isotopic substitution led to decreased reactivity, the rate const...

Recent developments in the chemistry of η3-allylruthenium(IV) complexes are due to their straightforward synthesis resulting from oxidative addition of allylic substrates to a ruthenium(II) center. Subsequent reaction with a nucleophile is the basis of their involvement in the catalytic allylic substitution reaction. We focus here on ruthenium-catalyzed substitution of allylic substrates by C-,...

A new class of conformationally rigid phosphino-oxazoline ligands 3 were synthesized via an efficient ortho-substitution of phenyl glycinol as the key step. Divergent synthetic routes for easy ligand modulation, as well as a procedure suitable for scale-up synthesis, were established. The catalytic potential of ligands 3 has been demonstrated in the highly enantioselective Ir-catalyzed hydrogen...

One major synthetic route to the synthesis of benzyl amines, ethers, and esters is the nucleophilic substitution of a benzylic halide. To develop a method for the facile synthesis and functionalization of the isosteric azaborines, 2-chloromethyl-2,1-borazaronaphthalene has been synthesized in one step to afford a similar common precursor to a benzylic halide. This B-N isostere has been shown to...

A seven-step total synthesis of Hagen's gland lactones 1 and 2 starting from 1,2-O-isopropylidene-alpha-D-xylofuranose 3 is reported. The success of this short and practical synthesis depends on the use of two key reactions: a stereoselective nucleophilic substitution at the anomeric position of 5 and 6, which allowed the construction of the gamma-lactone ring, and an alkyl substitution reactio...

Aryldiazo substituents were used in nucleophilic aromatic substitution reactions of halogens. The Ph-N=N- group activates ortho fluorine atoms toward alkylthiolation under mild conditions. In contrast, the Me(2)N-C(6)H(4)-N=N- group has virtually no activation effect in nucleophilic aromatic substitution, and serves as a "neutral" mask for the amino group. The Ph-N=N- group was efficiently intr...

Soot particles alter global climate and dominate the origin evolution of carbonaceous interstellar material. Convincing experimental evidence has linked polycyclic aromatic hydrocarbons (PAH) to soot inception under low-temperature astrochemistry high-temperature combustion conditions. However, significant gaps still remain in knowledge PAH formation mechanisms. Here, we report theoretical for ...

Sequential alkyne activation of terminal alkynes and propiolic acids by gold(I) catalysts yields compounds having α-pyrone skeletons. Novel cascade reactions involving propiolic acids are reported that give rise to α-pyrones with different substitution patterns.