| Summary: | PART I. The preparation of (-)-ibogamine (1) in fourteen steps from
benzoquinone and in 10% overall yield is a powerful illustration of the value of
the asymmetric Diels-Alder reaction as a starting point in a multistep synthesis.
All four cycloadducts, 70, 77, 84 and 96, obtained with the (S)-BINOL-TiCl���
complex were found to have the same absolute configuration. Furthermore, they
are in the same enantiomeric series that Mikami observed with 1,4-naphthoquinone using the same catalyst, lending confidence to future stereochemical predictions that may be made with this system.
PART II. Three different routes for the synthesis of the
hexahydroisoquinoline 98 met obstacles which defeated our approach to
koumine. The Diels-Alder reaction of cyclic 1-azadienes 102 and 108 was
abandoned due to the lack of reactivity of the dienes. An anionic oxy-Cope
rearrangement of the azabicyclo[2.2.2]octane system caused mainly
decomposition of the starting materials. Finally, an intramolecular [2+2]
photocycloaddition generated "crossed", "straight" and hydroisoquinoline
products in varying ratios, depending on the substituent pattern of the substrate,
but this approach was not synthetically useful. The results from this last study
may be valuable for predicting the regiochemical outcome of certain
intramolecular photocycloadditions. === Graduation date: 2003
|
|---|
