Ligularone

A synthesis of the furanoeremophilane ( )-ligularone has been accomplished via the intramolecular Diels-Alder reaction of an oxazole with an alkynic dienophile (81JA4611). The lactone (359) was treated with lithium methylisocyanide to yield the oxazole (360). Oxidation of alcohol to aldehyde and reaction of this unstable aldehyde with lithiopropyne gave a 55 45 mixture of diastereomeric alcohols (361). Oxidation of the mixture gave a single alkynic ketone (362) which when refluxed in ethylbenzene afforded the desired furanosesquiterpene (363 Scheme 78). 

The thermal reactions of furans merit only brief mention. Ligularone (5) is isomerized to isoligularone (6) without a catalyst at 260 °C and diradical intermediates have been postulated (73TL3999). The double bond of furan can be forced to participate in electrocyclic... 

Yamakawa et have converted the triketone (538) (by standard procedures) into the racemates of furanoeremophilane (539), furanoligularane (540), 9,10-dehydrofuranoeremophilane (541), ligularone (542), 3j8-hy-droxyfuranoeremophilane (543), and 3jS-furanoligularanol (544). An alternative... 

New examples of known rearrangements of 3-acylfurans have been described in which the ring opens and reforms on the acyl oxygen atom. The isomerization of 112 to 113 is effected by protic or Lewis acids,227 whereas the change from ligularone (114) to isoligularone(115), which occurs... 

A very neat method for the synthesis of furanoeremophilanes has been devised which incorporates a so-called bis-heteroannulation process.318 This is achieved by an intramolecular Diels-Alder reaction between an oxazole and an acetylenic grouping and is nicely demonstrated by the synthesis of ligularone (711) and petasalbine (712) (Scheme 67).319 A number of straightforward syntheses of... 

Synthesis. - Cycloadditions. A bis-heteroannelation approach to ( )-ligularone (90) from (89) has been reported. Other intramolecular cycloadditions include the conversions of (91) into (92) and the intramolecular addition to the benzyne (93), which is the key to the synthesis of ( )-mansonone (94). ... 

Synthesis of Evodone Synthesis of Ligularone and Petasalbine Synthesis of Paniculide-A Synthesis of Gnididione Synthesis of Norsecurinine Synthetic Approach to Geigerin Synthesis of Stemoamide Thiofurans and Amidofurans... 

Synthesis of Heterocycles. 1-Nitro-1-phenylthiopropene is an excellent reagent for the synthesis of furanoterpenoids. Condensation with /3-diketones and sulfoxide elimination gave ligularone and isoligularone, respectively (eq 7). The methods... 

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