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Ectoparasites of bats in Mongolia : Part 2 (Ischnopsyllidae, Nycteribiidae, Cimicidae and Acari)
(2012)
This study analyses ectoparasites found on Mongolian bats between 2008 and 2011. We examined 12 different bat species, with a total of 23 ectoparasite species present. Apart from reporting distributions, we also discuss specific host-parasite relationships. Owing to recent taxonomic changes splitting the Myotis mystacinus-group into several new taxa, their corresponding ectoparasite fauna could also be addressed in detail. Introducing ectoparasitic insects at length elsewhere (SCHEFFLER et al., 2010), this paper focuses on the analysis of parasitic Acari. Additional findings for Spinturnicidae (wing mites) and Macronyssidae broadened the spectrum of known parasites. Altogether, the knowledge of bat ectoparasites from Mongolia remains very sketchy. Based on different examples, we discuss current taxonomic problems regarding the species status of parasites, and suggest avenues for future research.
4,4-Dimethyl-1-(trifluoromethylsulfonyl)-1,4-azasilinane 1 and 2,2,6,6-tetramethyl-4-(trifluoromethylsulfonyl)- 1,4,2,6-oxazadisilinane 2 were studied by variable temperature dynamic 1H, 13C, 19F NMR spectroscopy and theoretical calculations at the DFT (density functional theory) and MP2 (Moller-Plesset 2) levels of theory. Both kinetic (barriers to ring inversion) and thermodynamic data (frozen conformational equilibria) could be obtained for the two compounds. The computations revealed two minima on the potential energy surface for molecules 1 and 2 corresponding to the rotamers with the CF3SO2 group directed inward and outward the ring, the latter being 0.20.4 kcal/mol (for 1) and 1.1 kcal/mol (for 2) more stable than the former. The vibrational calculations at the DFT and MP2 levels of theory give the values of the free energy difference Delta G degrees for the 'inward' reversible arrow 'outward' equilibrium consistent with those determined from the experimentally measured ratio of the rotamers. The structure of crystalline compound 2 was ascertained by X-ray diffraction analysis.
Syntheses of thiazolidine-fused heterocycles via exo-mode cyclizations of vinylogous N-acyliminium ions incorporating heteroatom-based nucleophiles have been examined and discussed. The formation of (5,6)-membered systems was feasible with all nucleophiles tried (O, S and N), while the closing of the five-membered ring was restricted to O- and S-nucleophiles. The closure of a four-membered ring failed. Instead, the bicyclic (5,6)-membered acetal derivative and the tricyclic system with an eight-membered central ring were obtained from the substrates containing O and S nucleophilic moieties, respectively. The reaction outcome and stereochemistry are rationalized using quantum chemical calculations at B3LYP/6-31G(d) level. The exclusive cis-stereoselectivity in the formation of (5,6)- and (5,5)-membered systems results from thermodynamic control, whereas the formation of the eight-membered ring was kinetically controlled.