Sequential reduction of the ketone and dehydration of the resulting alcohol
introduces a double bond. Hydrogenation then both reduces the unsatura-
tion and takes the nitro group on to the amine ( 121 ). The amino group is
then acylated with acetic anhydride. Reaction with permanganate intro-
duces a ketone at the alternate position from that remaining after cycliza-
tion ( 122 ). Reaction of this last intermediate with butyl nitrite in the
presence of strong base introduces nitrogen at the position adjacent
to the ketone in the form of an oxime ( 123 ). This group is then reduced to
the corresponding amine by means of zinc in acetic acid and anhydride.
This reaction affords the acetamide ( 124 ). Sequential hydrolysis of
the amides followed by acylation with trifluorcacetyl chloride yields the
amide ( 125 ). This last reaction is apparently specific for the amine adjacent
to the ketone, leaving that on the aromatic ring as a free amine. This bicyc-
lic compound is then condensed with the known total synthesis intermedi-
ate 126 , in the presence of acid to affordexatecan( 127 ).^15 Again, for
bookkeeping purposes, this last transform can be viewed as reaction of
the ketone in 126 with the aniline nitrogen and condensation of the result-
ing enamine with the tetralone carbonyl group.
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232 POLYCYCLIC FUSED HETEROCYCLES