Synthesis of Limonoid and Steroidal intermediates

The cyclopentyl intermediate 4 is an easily obtained, highly enantiopure starting material for the synthesis of numerous triterpenoids. Prepared from (+)-endo-3-bromocamphor (2) in a four-step sequence, 4 has been converted into two advanced triterpenoid intermediates. In an eleven-step sequence 4 was transformed into the bicyclic intermediate (42) that could be used in an enantiospecific approach to the limonoids. The enone 42 was subsequently dialkylated in a regio- and stereoselective manner to produce the intermediate 45. Removal of the silyl protecting group followed by oxidation and acid-catalysed annulation produced the tricyclic enone 53. Structure 53 represents a highly advanced ent-limonoid intermediate with correct relative and absolute stereochemistry with obvious similarities to limonoids such as ent-azadirone (6). Further investigations illustrated 4's utility in the synthesis of the steroidal hydrindane system. Using an analogous pathway 4 was again converted to a bicyclic enone 104 in eight steps. Regiospecific alkylation followed by medium pressure hydrogenation and epimerization yielded the hydrindane 110. Extensive NMR analysis of this compound was used to provide conclusive evidence of 110's absolute stereochemistry. This route is therefore potentially useful in an approach to natural products such as 1α, 25-Dihydroxyvitamin D₃ (58).

Name thesis:degree_name

Master of Science - MSc

Level thesis:degree_level

master's

Discipline thesis:degree_discipline

Chemistry

Grantor dc:publisher

University of British Columbia

Year dc:date

1993

Author dc:creator

• Richardson, Scott Rowand

Statement dc:rights

• For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.

Language dc:language

eng

Handle dc:identifier

http://hdl.handle.net/2429/1430

OAI identifier oai:identifier

oai:circle.library.ubc.ca:2429/1430