Synthetic studies of swazinecic acid dilactone
- Authors: Liddell, James Richard
- Date: 1989
- Subjects: Phrrolizidines Alkaloids -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4298 , http://hdl.handle.net/10962/d1004668
- Description: The occurrence and syntheses of the pyrrolizidine alkaloids from 1976 to March 1988 is reviewed, and a stereoselective total synthesis of swazinecic acid dilactone was attempted. One approach involved an asymmetric synthesis of the allylic α-hydroxy acid 2-hydroxy-2,3-dimethyl-3-butenoic acid employing oxazolines as chiral auxilaries. The oxazoline, (4S,5S)-2-(1-bromoethyl)-4-methoxymethyl-5-phenyl-2-oxazoline, was obtained by direct halogenation of the 2-ethyl oxazoline analogue. This was condensed with acetone in a Darzens type reaction and the resultant epoxy oxazoline rearranged to an allylic α-hydroxy oxazoline which was then hydrolysed to the chiral hydroxy acid in low enantiomeric excess. The hydroxy acid, as the O-silylated ethyl ester, was elaborated by allylic diethyl malonate to bromination and condensation with diethyl 5-carboethoxy-2-methyl-3- methylene-2-0-tert-butyldimethylsilylhexanedioate. Removal of the silyl protecting group and epoxidation provided an epoxy triester, which on hydrolysis provided a mixture of acids of uncertain structures.
- Full Text:
- Date Issued: 1989
- Authors: Liddell, James Richard
- Date: 1989
- Subjects: Phrrolizidines Alkaloids -- Synthesis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4298 , http://hdl.handle.net/10962/d1004668
- Description: The occurrence and syntheses of the pyrrolizidine alkaloids from 1976 to March 1988 is reviewed, and a stereoselective total synthesis of swazinecic acid dilactone was attempted. One approach involved an asymmetric synthesis of the allylic α-hydroxy acid 2-hydroxy-2,3-dimethyl-3-butenoic acid employing oxazolines as chiral auxilaries. The oxazoline, (4S,5S)-2-(1-bromoethyl)-4-methoxymethyl-5-phenyl-2-oxazoline, was obtained by direct halogenation of the 2-ethyl oxazoline analogue. This was condensed with acetone in a Darzens type reaction and the resultant epoxy oxazoline rearranged to an allylic α-hydroxy oxazoline which was then hydrolysed to the chiral hydroxy acid in low enantiomeric excess. The hydroxy acid, as the O-silylated ethyl ester, was elaborated by allylic diethyl malonate to bromination and condensation with diethyl 5-carboethoxy-2-methyl-3- methylene-2-0-tert-butyldimethylsilylhexanedioate. Removal of the silyl protecting group and epoxidation provided an epoxy triester, which on hydrolysis provided a mixture of acids of uncertain structures.
- Full Text:
- Date Issued: 1989
The development of the political party system in the Ciskei
- Authors: Ka Tywakadi, Gordon Renton
- Date: 1978 , 2013-10-17
- Subjects: Political parties -- South Africa -- Ciskei , Elections -- South Africa -- Ciskei
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2853 , http://hdl.handle.net/10962/d1006868 , Political parties -- South Africa -- Ciskei , Elections -- South Africa -- Ciskei
- Description: (p. 1) The Ciskei homeland, which is a 'sub-state' of the Republic of South Africa, attained a semi-autonomous status as a result of the implementation of the Bantustan policy of the Government of the Republic of South Africa. This semi-autonomous status introduced a Westminster type of parliamentary system which in turn brought into being a political party system. The purpose of this thesis is to investigate, amongst other things, the roles played by these political parties:- i) What role would the political parties play in the struggle of the Ciskeians for equal political rights vis - a-vis white South Africa? ii) Whose interests would those political parties serve? iii) This semi-autonomous status has resulted in the juxtaposing of traditional and modern political institutions. The political institutions that have emerged, include inter alia, legislative assemblies and political parties. These modern political institutions have been superimposed on traditional political institutions. What effect(s) would the one have on the other? iv) Would the development of political parties lead to the establishment of a one, two or dominant party system? In order that the above questions may be answered, i) An attempt will be made to define a political system, illustrating the concept with examples taken from the Republic of South Africa political scene and at the same time, attention will be directed to the relationship between the Republic of South Africa and the Ciskei. ii) When investigating the political party and the political party system, the role played by the political parties and the political party system in the relationship between the Republic of South Africa and the Ciskei will be defined. , Ciskei (South Africa) -- Politics and government , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 1978
- Authors: Ka Tywakadi, Gordon Renton
- Date: 1978 , 2013-10-17
- Subjects: Political parties -- South Africa -- Ciskei , Elections -- South Africa -- Ciskei
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2853 , http://hdl.handle.net/10962/d1006868 , Political parties -- South Africa -- Ciskei , Elections -- South Africa -- Ciskei
- Description: (p. 1) The Ciskei homeland, which is a 'sub-state' of the Republic of South Africa, attained a semi-autonomous status as a result of the implementation of the Bantustan policy of the Government of the Republic of South Africa. This semi-autonomous status introduced a Westminster type of parliamentary system which in turn brought into being a political party system. The purpose of this thesis is to investigate, amongst other things, the roles played by these political parties:- i) What role would the political parties play in the struggle of the Ciskeians for equal political rights vis - a-vis white South Africa? ii) Whose interests would those political parties serve? iii) This semi-autonomous status has resulted in the juxtaposing of traditional and modern political institutions. The political institutions that have emerged, include inter alia, legislative assemblies and political parties. These modern political institutions have been superimposed on traditional political institutions. What effect(s) would the one have on the other? iv) Would the development of political parties lead to the establishment of a one, two or dominant party system? In order that the above questions may be answered, i) An attempt will be made to define a political system, illustrating the concept with examples taken from the Republic of South Africa political scene and at the same time, attention will be directed to the relationship between the Republic of South Africa and the Ciskei. ii) When investigating the political party and the political party system, the role played by the political parties and the political party system in the relationship between the Republic of South Africa and the Ciskei will be defined. , Ciskei (South Africa) -- Politics and government , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 1978
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