Titanium-catalyzed hydroamination of 1,4-and 1,5-diynes by primary amines leads to imino-alkynes that undergo in situ 5-endo dig and 5-exo dig cyclization reactions, respectively. The products are 1,2,5-trisubsituted pyrroles accessed directly from readily available diyne starting materials.New synthetic strategies for the generation of substituted pyrroles are of continuous interest due to the ubiquity of this heterocycle in natural products and pharmaceuticals. 1 We have been exploring new reactions based on titaniumcatalyzed intermolecular hydroamination 2,3 using a selection of pyrrolyl-based ancillary ligands. In the course of previous studies, new protocols for the synthesis of hydrazones, indoles, 4,5 and R, -unsaturated iminoamines 6 have been discovered. In this paper, it is reported that the readily prepared, inexpensive titanium catalysts Ti(NMe 2 ) 2 (dpma) (A) and Ti(NMe 2 ) 2 (dmpm) (B) (Scheme 1) can be used in the monohydroamination of 1,4-and 1,5-diynes, which then undergo cyclization to the corresponding pyrroles. These pyrrole syntheses are an expansion of CuCl-catalyzed 1,3-diyne reactions with primary amines to generate similar products. 7 The pyrrolyl-based catalyst Ti(NMe 2 ) 2 (dpma) (A), 8,9 which has an X 2 L ancillary ligand 10 set (Scheme 1), has been examined for a variety of hydroamination applications by our group. The H 2 dpma ligand is prepared in a single step by a Mannich reaction between 2 equiv of pyrrole, 2 equiv of formaldehyde, and methylamine hydrochloride. 11 The most active catalyst known to date is the dipyrrolylmethane (1) For reviews see: (a) Gilchrist, T. L.
Two alpha2-adrenoceptor agents, xylazine and medetomidine, in combination with midazolam and ketamine safely and effectively immobilized Siberian tigers (Panthera tigris altaica). The medetomidine protocol used smaller drug volumes, and induction and recovery times were shorter. Although cardiopulmonary abnormalities were noted, none were likely to be life threatening.
ABSTRACT:We report the first documented case of morbillivirus infection in a wild, freeranging Siberian tiger (Panthera tigris altaica). The tigress entered a small village in the Russian Far East in an ambulatory but stuporous state with no apparent recognition or fear of humans. Her condition progressed rapidly with neurological signs, anorexia, and ultimately death. Histologic lesions included vacuolated to malacic white matter in the brain stem, cerebellum, and thalamus, with associated lymphocytic meningoencephalitis. Large, intranuclear, eosinophilic inclusions were within regional astrocytes, and the brain lesions were immunohistochemically positive when stained for canine distemper viral antigen. Hematologic and blood chemistry results were consistent with overwhelming systemic infection and starvation. The animal also was antibody-positive for canine distemper virus, feline panleukopenia, and feline coronavirus.
A comparison of the amino acid sequences demonstrated that Siberian tiger gonadotropins are more homologous with those of porcine than any other commercially available preparation. The present study measured the efficacy of repeated ovarian stimulation with purified porcine gonadotropins on the follicular, hormonal, and immunogenic responses in Siberian tigers as well as on the ability of oocytes retrieved by laparoscopic follicular aspiration to fertilize and cleave in vitro. Controlled rate and vitrification cryopreservation methods were also compared for their ability to support ongoing cleavage following thawing of presumptive 2- to 4-cell tiger embryos generated in vitro. Vitrification supported continued embryonic cleavage in vitro while controlled rate freezing did not. Stereological microscopy indicated an excellent ovarian response with the recovery of quality cumulus-oocyte complexes that apparently fertilized and cleaved in vitro. However, ultrastructural and physiological examination revealed abnormal and unnatural responses such as the failure of some cumulus-oocyte complexes to reach maturity and progestagen levels to approach normalcy. At the same time, analyses of blood for antibodies failed to detect an immune reaction to these foreign gonadotropins in an assay that tested positive for the chorionic gonadotropin-stimulated domestic cat. Together, these observations suggest that porcine gonadotropins may be effective for the ovarian stimulation of tigers but that some modifications to administration protocols are needed to produce a more natural response.
Six bengal tigers (Panthera tigris tigris) were immobilized five times at 2-wk intervals with ketamine hydrochloride (ketamine) and xylazine hydrochloride (xylazine) mixtures at different dose levels. Hematology and serum chemistry analyses on blood samples collected at each immobilization remained normal during the study. There were acute changes in hematocrit, chloride, potassium, glucose, and bilirubin as a function of xylazine dose level. The effect of yohimbine hydrochloride (yohimbine) on the depth and duration of immobilization was evaluated in a crossover design with every animal serving as its own control at each dose. Administration of yohimbine resulted in recovery of the animals within 4-8 min in contrast to greater than 60 min with no yohimbine treatment. There were no adverse effects noted with the yohimbine treatment and the tigers did not exhibit a relapse over the next 24 hr. Yohimbine at a dose of 5-15 mg per adult tiger provided effective reversal of 50-150 mg of xylazine per tiger.
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