Asymmetric Tandem Additions to Chiral 2,3-Dihydronaphthyloxazolines: Synthesis of the Triptoquinone/Triptinin A Ring System

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.

ring closing metathesis - alkyllithiums - chiral oxazolines - conjugate additions - deoxygenation - triflates - tetralones

References

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Scheme 11

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