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Title: Synthetic studies towards pinguisone
Author: Webster, Nigel Martin Henry
ISNI:       0000 0001 3565 167X
Awarding Body: University of Southampton
Current Institution: University of Southampton
Date of Award: 1986
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The novel structure and antifeedant activity of the furanosesquiterpene pinguisone make it an interesting synthetic target. The approach described in this work involves a [4+2]cycloaddition as the key reaction in constructing the correct indene skeleton. Whereas 1-methoxy-3-trimethyl-siloxybuta-1,3-diene (Danishefsky's diene) was completely unreactive towards 2,3,4-trimethyl-2-cyclopentenone, Diels-Alder cycloaddition was found to occur at very high pressure (13-15 kBar) with the more reactive dienophile methyl 2,3-dimethyl-5-oxo-1-cyclopentene-1-carboxylate giving after hydrolysis (3R*,3aS*,7aR*)-methyl 3,3a-dimethyl-1,5(4H)-dioxo-2,3,3a,7a-tetrahydroindene-7a-carboxylate in good yield. The structure of this was confirmed by X-ray diffraction. Reaction of the lithium enolate of the diene with the more reactive dienophile at low temperatures gave one Michael addition only; however, the resulting ketoester was converted to the desired indene intermediate in a good overall yield. Model studies provided a route which when applied to the indene intermediate enabled an efficient conversion (3R*,3aS*,7aS*)-2,3,3a-7a-tetrahydro-3,3a,7a-trimethylindene-1,5(4H)-dione. Conjugate addition with lithium dimethylcuprate gave the undesired epimer exclusively which on further elaboration gave 4-epipinguisone and 4-epipinguisanol.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Organic chemistry