A study of flow characteristics in a circular sedimentation tank under the influence of a forced vortex

Imperial Users onl

Studies toward the total synthesis of alkaloids : nagelamide A and D, agelastatin D, dragmacidin A-C, salacin and almazoles

Studies toward the total syntheses of highly potent cytotoxic alkaloids including the bromopyrrole alkaloids and indole alkaloids were conducted and are described. Studies carried out in the course of this dissertation consist of five total syntheses of natural products that include bromopyrrole alkaloids nagelamide A, D and agelastatin D as well as indole-based alkaloids dragmacidin A-C, salacin and almazoles. The total synthesis of dimeric bromopyrroles, nagelamide A, was achieved in 8 steps from ornithine by using NCS oxidative dimerization of 2-aminoimidazole as a key step. The total synthesis of nagelamide D was accomplished in 6 steps using acidpromoted dimerization as a key feature. These methods provide a short and rapid entry into the syntheses of nagelamides without the use of protecting groups on nitrogen. In studies toward the synthesis of agelastatin D, the ABD-ring system was derived from a β–functionalization of linear imidazolone. The studies carried out in the course of this thesis have set in place a major ABD-ring core for the agelastatin D. Only the construction of the C-ring through a one-carbon bridge remains to be done. In the synthesis of bisindole alkaloids, a short synthetic strategy for dragmacidin A, B and C was accomplished by involving the dimerization of oxotryptamines to give bis(indolyl)pyrazines, which upon reduction and selective methylation with sodium cyanoborohydride in acetic acid or formic acid afforded the target piperazine natural products as the key steps. The application of the interrupted Pictet-Spengler cyclization involving halotryptamine spirocyclization with aldehydes having various functionalities has been investigated. The methodology appears to work well with aldehydes containing alcohol or ester groups but not with ketones or protected aldehydes. Furthermore, we have demonstrated the synthesis of salacin via halotryptamine spirocyclization. A short synthesis of almazole C and D are described. The key steps involve the peptide coupling and Gabriel-Robinson oxazole synthesis with chiral, nonracemic ketoamides. An integral aspect of the research involves the preparation of the key β–oxotryptophan synthon and demonstration of its utility. These investigations have lead to a revision of the structure of almazole D as 5-(3-indolyl)oxazole

Western knowledge and intellectual groups in Japan and Thailand in the nineteenth century: the Meirokusha and Young Siam

Thesis (Ph. D.)--University of Washington, 1990In the nineteenth century Japan and Thailand were confronted by serious challenges from the West as well as the threat of imperialism. The Meirokusha and the Young Siam were intellectual groups who introduced Western ideas and institutions into their respective countries. Their family background, educational background and their attitudes toward their own societies and the West strongly effected the modernization of these two countries.Most of the Meirokusha came from the lower samurai class who were educated both in traditional and Western knowledge, especially Western sciences. Some of them such as Nishi Amane, Tsuda Mamichi and Nakamura Keiu, also had a chance to study abroad. Because of socio-political changes in the late Tokugawa period they were alienated from the traditional system and started looking to the West for models.The family background of the Young Siam were very different from that of the Meirokusha. They came from royal families and the noble class and were taught both traditional and Western knowledge. Their level of Western knowledge, especially in the sciences, was not as intensive as that of the Meirokusha. Their feeling toward their own society and the West was also different from that of the Meirokusha. They were still satisfied with their own society and accepted Western ideas only in a limited way.The differences in their level of Western knowledge and their feelings toward their own society and the West caused them to differ in their ideas about modernization. The Meirokusha wholeheartedly accepted Western socio-political and economic philosophies such as natural rights, freedom and individualism. Japanese society underwent a rapid change in accepting Western culture. In contrast, Thai modernization occurred slowly. The Young Siam used traditional values such as kingship and unity to counter balance Western influences. They accepted only Western political institutions and technology. New political ideas did not penetrate into Thai society. Their national identities were formulated in this period.We can compare the results of the Meirokusha's and the Young Siam's ideas in modernization of their countries, the Meirokusha brought new ideas and institutions into Japanese society. Japan underwent socio-political and economic transformations which laid down a strong foundation for later development. Thai socio-political reforms resulted in an absolute state. Thailand remained an agrarian society, while Japan was developing into an industrial country