- Title
- Synthetic studies of swazinecic acid dilactone
- Creator
- Liddell, James Richard
- ThesisAdvisor
- Whiteley, C.G.
- Subject
- Phrrolizidines Alkaloids -- Synthesis
- Date
- 1989
- Type
- Thesis
- Type
- Doctoral
- Type
- PhD
- Identifier
- vital:4298
- Identifier
- 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.
- Format
- 290 p., pdf
- Publisher
- Rhodes University, Faculty of Science, Chemistry
- Language
- English
- Rights
- Liddell, James Richard
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Collections
RU Department of Chemistry
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