PART I. Asymmetric syntheses of both natural (+)- and nonnatural (-)-
byssochlamic acid via a [2+2] photoaddition-cycloreversion strategy are
described. X-ray crystallographic analysis of the cyclohexylamine salt 99 showed
that the structure of the monomethyl ester 100 from esterase hydrolysis of 44
was originally misassigned as 56. The enantiomeric relationship of the two
diolides 106 and 70 permitted syntheses of nonnatural byssochlamic acid (-)-3
and natural byssochiamic acid (+)-3 from enantiopure alcohol (+)-64 and from its
enantiomer (-)-110, respectively. Through the use of (��)-103 to reach both
enantiomers of byssochlamic acid (3) and subsequent epimerization of the npropyl
chain, it was proved that the cis configuration of the two alkyl substituents
is strongly preferred in the natural product.
PART II. An asymmetric approach towards the nootropic agent huperzine A
is described. Formation of cyclobutane 122 with the desired stereochemistry was
accomplished using intramolecular [2+2] photoaddition of the enantiopure enone
121. Attempts to prepare the methoxypyridine system via an azadiene Diels-
Alder reaction were unsuccessful. However, intramolecular Michael addition of
181 produced silyl ether 182 which was converted into the pyridone 187 by
treatment with hydrogen fluoride followed by selenoxide elimination. Attempts to
effect the key sigmatropic rearrangement of ketone 197 into a direct precursor of
huperzine A were unsuccessful. / Graduation date: 2001
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32732 |
| Date | 02 November 2000 |
| Creators | Kim, Jungchul |
| Contributors | White, James D. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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