Synthesis of furanosesquiterpenoid natural products

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Description/Abstract

The effect of addition of a catalytic quantity of a crown ether in the reaction of a phosphonate anion with a carbonyl compound (Wadsworth-Emmons reaction) has been studied and found to greatly facilitate this reaction. This modification of the Wadsworth-Emmons reaction, using a catalytic amount of 15-crown-5, has been employed in the synthesis of the naturally occurring furanosesquiterpene Pallescensin-E. The structure of this compound has been confirmed by comparison of its spectral data with that of the synthesised isomer, 4,l0-dihydro-7,8-dimethyl 10H-benzof4,5Jcycloheptafl,2-bJ furan.

Homosesquirosefuran, an analogue of the naturally occurring furanosesquiterpene Sesquirosefuran, has been synthesised via the dianion of methylacetoacetate.

An approach to the synthesis of Pinguisone (a component of the essential oil of the liverwort Aneura pinguis)has been attempted employing two Diels-Alder reactions to generate the four cis-methyl groups found in the natural product.

In a study of the reaction of n-(2-methylallyl)nickel bromide complex with a range of epoxides, this complex was found not only to react with reactive epoxides (e.g. styrene epoxide) but also with less reactive propylene epoxide.

Substrates for possible intramolecular n-allylnickel cyclisation to generate an a-methylene-6-valerolactone ring system have been prepared.