Enantioselective Synthesis of Succinimides by Michael Addition of 1,3-Dicarbonyl Compounds to Maleimides Catalyzed by a Chiral Bis(2-aminobenzimidazole) Organocatalyst

A wide variety of chiral succinimides have been prepared in high yields and enantioselectivities by asymmetric conjugate addition of 1,3-dicarbonyl compounds to maleimides under very mild reaction conditions using a bifunctional benzimidazole-derived organocatalyst. Computational and NMR studies support the hydrogen-bonding activation role of the catalyst and the origin of the stereoselectivity of the process.

Silver-catalysed multicomponent 1,3-dipolar cycloaddition of 2-oxoaldehydes-derived azomethine ylides

The silver-catalysed multicomponent reaction between ethyl glyoxylate, 2,2-dimethoxyacetaldehyde, or phenylglyoxal as aldehyde components with a α-amino ester hydrochloride and a dipolarophile in the presence of triethylamine is described. This domino process takes place at room temperature by in situ liberation of the α-amino ester followed by the formation of the imino ester, which is the precursor of a metalloazomethine ylide. The cycloaddition of this species and the corresponding dipolarophile affords polysubstituted proline derivatives. Ethyl glyoxylate reacts with glycinate, alaninate, phenylalaninate and phenylglycinate at room temperature in the presence of representative dipolarophiles affording endo-2,5-cis-cycloadducts in good yields and high diastereoselection. In addition, 2,2-dimethoxyacetaldehyde is evaluated with the same amino esters and dipolarophiles, under the same mild conditions, generating the corresponding endo-2,5-cis-cycloadducts with higher diastereoselections than the obtained in the same reactions using ethyl glyoxylate. In the case of phenylglyoxal the corresponding 5-benzoyl-endo-2,5-cis cycloadducts are obtained in short reaction times and similar diasteroselection.

2-Aminobenzimidazole Organocatalyzed Asymmetric Amination of Cyclic 1,3-Dicarbonyl Compounds

The use of a trans-cyclohexanediamine benzimidazole derivative as a hydrogen-bond catalyst for the electrophilic amination of cyclic 1,3-dicarbonyl compounds is herein presented. High yields and enantioselectivities varying from moderate to excellent are generally obtained using mild reaction conditions and as low as 1 mol% of catalyst loading.

Organocatalytic Asymmetric α-Chlorination of 1,3-Dicarbonyl Compounds Catalyzed by 2-Aminobenzimidazole Derivatives

Bifunctional chiral 2-aminobenzimidazole derivatives 1 and 2 catalyze the enantioselective stereodivergent α-chlorination of β-ketoesters and 1,3-diketone derivatives with up to 50% ee using N-chlorosuccinimide (NCS) or 2,3,4,4,5,6-hexachloro-2,5-cyclohexadien-1-one as electrophilic chlorine sources.

(Tables 1-3) Amphipod species observed under Antarctic pack ice during POLARSTERN cruises ANT-XXI/4, ANT-XXII/2 and ANT-XXIII/6

During three Antarctic expeditions (2004, ANT XXI-4 and XXII-2; 2006, ANT XXIII-6) with the German research icebreaker R/V Polarstern, six different amphipod species were recorded under the pack ice of the Weddell Sea and the Lazarev Sea. These cruises covered Austral autumn (April), summer (December) and winter (August) situations, respectively. Five of the amphipod species recorded here belong to the family Eusiridae (Eusirus antarcticus, E. laticarpus, E. microps, E. perdentatus and E. tridentatus), while the last belongs to the Lysianassidea, genus Cheirimedon (cf. femoratus). Sampling was performed by a specially designed under-ice trawl in the Lazarev Sea, whereas in the Weddell Sea sampling was done by scuba divers and deployment of baited traps. In the Weddell Sea, individuals of E. antarcticus and E. tridentatus were repeatedly observed in situ during under-ice dives, and single individuals were even found in the infiltration layer. Also in aquarium observations, individuals of E. antarcticus and E. tridentatus attached themselves readily to sea ice. Feeding experiments on E. antarcticus and E. tridentatus indicated a carnivorous diet. Individuals of the Lysianassoid Cheirimedon were only collected in baited traps there. Repeated conventional zooplankton hauls performed in parallel to this study did not record any of these amphipods from the water column. In the Lazarev Sea, E. microps, E. perdentatus and E. laticarpus were regularly found in under-ice trawls. We discuss the origin and possible sympagic life style of these amphipods.

Dinoflagellate cysts in surface sediment samples of METEOR cruises M20/2, M23/1, M34/1, M34/2, M34/3 and M34/4

To enhance the limited information available about the palaeo-ecological significance of calcareous dinoflagellates, we have studied their lateral distribution in surface sediments of the equatorial and south Atlantic between 13°N and 36°S. Calcareous dinoflagellate cysts appear to be widely distributed throughout the studied area. In the surface sediments, concentrations (cyst per gram dry sediment) of the vegetative stage Thoracosphaera heimii are generally higher than that of the (presumably) calcareous resting cysts. Distribution patterns in surface sediments of Orthopithonella granifera (Fütterer) Keupp and Versteegh, Rhabdothorax spp. Kamptner., Sphaerodinella albatrosiana (Kamptner) Keupp and Versteegh S. albatrosiana praratabulated, Sphaerodinella tuberosa var. 1 (Kamptner) Keupp and Versteegh and S. tuberosa var. 2 and the ratios between these species have been compared with temperature, salinity, density and stratification gradients in the upper water column. Rhabdothorax spp. is characteristically present in sediments of more temperate regions characterized by high seasonality. Dinoflagellates producing these cysts are able to tolerate high nutrient concentrations, and mixing of the water column. S. albatrosiana is abundant in regions characterized by high sea surface temperatures and oligotrophic surface water conditions. In contrast, the distribution of S. tuberosa var. 2 is negatively related to temperature. The other cyst species did not show a characteristic pattern in relation to the studied environmental gradients. The ratio of Sphaerodinella tuberosa var. 2 to Orthopithonella granifera can be used for reconstructing the presence of stratification in the upper 50 m of the water column, whereas the ratios of S. tuberosa var. 2 to Sphaerodinella albatrosiana and of O. granifera to Rhabdothorax spp. might be used for palaeotemperature reconstructions. Calcareous dinoflagellate cysts are abundant in oligotrophic areas and may be useful for the reconstruction of palaeoenvironmental conditions.

Injunctions against illegitimate labor practices and outlawing racketeering : Hearings before Subommittee no. 3, 77th Cong. 2d sess., April 2 - May 1, 1942.

Serial no. 17.

Task 5 report of tests 5.1, 5.2, and 5.3 for development of compliance test for truck rear underride protection. Interim report.

National Highway Traffic Safety Administration, Washington, D.C.