Asymmetric Synthesis of Functionalized α-Amino Acid Derivatives via the γ-Pyrone Carbaldimine-Based Organocatalytic Mannich Reaction.

A powerful synthetic strategy for the asymmetric synthesis of enantiomerically enriched γ-functionalized α-amino acid derivatives based on the highly stereoselective proline-catalyzed Mannich-type reaction of pre-prepared or -generated γ-pyrone-derived aldimines with carbonyl compounds and subsequent transformations of multifunctional reaction products has been developed. A significant positive nonlinear effect was detected for the key organocatalytic reaction. The developed strategy was applied for facile gram-scale preparation of ()-γ-oxonorvaline, used for site-specific modification of proteins, and both enantiomers of amycolatolide A recently isolated from the lichen-derived actinomycete sp.

Concise enantioselective synthesis of non-proteinogenic α-aminoacids an organocatalytic Mannich-type reaction.

A bifunctional tertiary amine-squaramide-catalyzed enantioselective Mannich-type addition of available allomaltol to -protected aldimines was developed. The resulted adducts were readily transformed into non-proteinogenic α-amino acids and their derivatives were not easily accessible by other methods oxidative fragmentation, esterification, amidation and deprotection reactions. The absolute ()-configuration of the thus obtained α-amino acids was established by comparison of the -Ts-PheGly optical rotation sign with the reported data.

Nitration of aromatics with dinitrogen pentoxide in a liquefied 1,1,1,2-tetrafluoroethane medium.

Regardless of the sustainable development path, today, there are highly demanded chemical productions still operating that bear environmental and technological risks inherited from the previous century. The fabrication of nitro compounds, and nitroarenes in particular, is traditionally associated with acidic wastes formed in nitration reactions exploiting mixed acids. However, nitroarenes are indispensable for industrial and military applications.

2-Nitroallyl carbonate-based green bifunctional reagents for catalytic asymmetric annulation reactions.

2-Nitroallylic carbonates, a new class of "green" 1,3-bielectrophilic reagents for organic synthesis and catalysis, have been prepared. The bifunctional tertiary amine-catalyzed asymmetric [3 + 3] annulations of cyclic enols with these reagents occur much faster than corresponding reactions with 2-nitroallylic esters and produce no acidic by-products poisoning the catalyst. Furthermore, 2-nitroallylic carbonates enable highly enantioselective one-pot synthesis of a variety of fused dihydropyrane derivatives from available precursors bearing pharmacophoric fragments.

Supercritical Antisolvent Processing of Nitrocellulose: Downscaling to Nanosize, Reducing Friction Sensitivity and Introducing Burning Rate Catalyst.

A supercritical antisolvent process has been applied to obtain the nitrocellulose nanoparticles with an average size of 190 nm from the nitrocellulose fibers of 20 μm in diameter. Compared to the micron-sized powder, nano-nitrocellulose is characterized with a slightly lower decomposition onset, however, the friction sensitivity has been improved substantially along with the burning rate increasing from 3.8 to 4.