Silica gel and microwave-promoted synthesis of dihydropyrrolizines and tetrahydroindolizines from enaminones.

A wide range of -(ethoxycarbonylmethyl)enaminones, prepared by the Eschenmoser sulfide contraction between -(ethoxycarbonylmethyl)pyrrolidine-2-thione and various bromomethyl aryl and heteroaryl ketones, underwent cyclization in the presence of silica gel to give ethyl 6-(hetero)aryl-2,3-dihydro-1-pyrrolizine-5-carboxylates within minutes upon microwave heating in xylene at 150 °C. Instead of functioning as a nucleophile, the enaminone acted as an electrophile at its carbonyl group during the cyclization. Yields of the bicyclic products were generally above 75%.

Demethylative Lactonization Provides a Shortcut to High-Yielding Syntheses of Lamellarins.

Modular gram-scale syntheses of the trimethyl ethers of lamellarins G () and D () were achieved from readily accessible precursors in the highest overall yields reported to date (, six steps, 82%; , seven steps, 86%). A novel demethylative lactonization between an aryl methyl ether and a neighboring carboxylic acid was developed for creating the chromenone unit of the targets to avoid the need for additional protection and deprotection steps. The central pyrrole core was constructed in a late-stage [4 + 1] condensation between ethyl bromoacetate and an enaminone possessing the remaining components of the lamellarin skeleton.

A Xylochemically Inspired Synthesis of Lamellarin G Trimethyl Ether via an Enaminone Intermediate.

A concise high yielding synthesis of lamellarin G trimethyl ether has been achieved from precursors and solvents that can in principle be derived from xylochemical (woody biomass) sources. The route is comparatively green in that some reactions are performed without solvent or with relatively benign solvents. In addition, chromatographic purification of products is avoided, and only a single aqueous workup is performed.

Biological induced corrosion of materials II: new test methods and experiences from MIR station.

During previous long-term manned missions, more than 100 species of microorganisms have been identified on surfaces of materials (bacteria and fungi). Among them were potentially pathogenic ones (saprophytes) which are capable of active growth on artificial substrates, as well as technophilic bacteria and fungi causing damages (destruction and degradation) to various materials (metals and polymers), resulting in failures and disruptions in the functioning of equipment and hardware. Aboard a space vehicle some microclimatic parameters are optimal for microorganism growth: the atmospheric fluid condensate with its specific composition, chemical and/or anthropogenic contaminants (human metabolic products, etc.