Abstract
A study to reach the diterpenoid (+)-triptoquinone A
(3 ) or its analog (+)-triptinin
A (4 ) via an asymmetric tandem addition to
naphthyloxazolines is described. The tandem addition to the chiral
dihydronophthalene 6 resulted in a 70% yield
of a single diastereomer 10 . Further manipulation
gave the natural products’ tricyclic ring system, compounds 20 and 29 via
ring-closing metathesis in 90% yield, using the Schrock
catalyst. Final assault to the target compounds 3 or 4 fell short due to the failure to either
reduce a neopentyl hydroxymethyl group to a methyl or to install
the conjugated carboxylic acid present in 3 or 4 .
Key words
ring closing metathesis - alkyllithiums - chiral
oxazolines - conjugate additions - deoxygenation - triflates - tetralones
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