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2,3,3aα,4,5,5a,6,9,9aα,9bβ-Decahydro-3α,9α-dimethyl-5aβ-methoxycarbonyl-2-oxonaphtho[2,3-b]furan (2) accessible from α-santonin was transformed into (+)-deoxyvernolepin (1). The preparation of some α-methylenelactones related to 1has also been described.

?-Acyl- and related d-lactones having no 6 substituents were synthesized in a sequence of reactions, 1,4-conjugate additions of sulfurstabilized acetate anions to a,ß-unsaturated ketones, followed by trapping of the resultant ketone enolates with formaldehyde, mild lactonization, and desulfurization.

The electrophilic reactivity of 2-(phenylthio)-2-penten-5-olide toward some benzylic Grignard reagents was investigated, and 2-methylene-3-(2,6-dimethylbenzyl)-5-pentanolide (secocrispiolide) was synthesized from one of the Michael adducts.

Upon heating in formic acid dolabradiene (1) gives a mixture of hydrocarbons. Five backbone rearrangement products isolated from the mixture are assigned to ?5(10)-8ß-rimuene (2), ?5(10)-rimuene (3), ?1(10)-rimuene (4), ?8(9)-pimaradiene (5), and ?1(10),5-rimutriene (6a), respectively. Their formation mechanisms are also discussed.

The total synthesis of diarylheptanoids isolated from the male flowers of Alnus sieboldiana, yashabushiketol, yashabushiketodiol A, yashabushiketodiol B, and yashabushitriol, has been achieved in short steps by employing the organoselenium-mediated reduction of epoxy ketone as key steps.

(1R,5S)-3-Phenylsulfenyl-6,6-dimethylbicyclo[3.1.1]heptanone obtained from (+)-nopinone was transformed into (1R,4S,5S)-4-methyl-4-vinylbicyclo[3.1.1]heptan-2-one, whose cyclobutane ring was cleaved with BF3·EtO2–Zn(OAc)2in acetic anhydride to provide (4S,5S)-1-acetoxy-4-isopropenyl-5-methyl-5-vinyl-1-cyclohexene (5), the key intermediate, in a highly regio- and stereoselective manner. Regioselective introduction of a three-carbon unit to 5with acetone followed by dehydration yielded (+)-ß-elemenone.

11-Acetoxy-12ba-methoxymethyl-4,4,6aa,9-tetramethyl-1,2,3,4,4aa,5,6,6a, 12aß,12b-decahydro-12H-benzo[a]xanthene (34), which has been expected as a promising key intermediate for the synthesis of siccanin (1), was synthesized via acid-catalyzed cyclization of 1a-(2-hydroxy-6-methoxy-4-methylbenzyl)-8aa-methoxymethyl-2,5,5-trimethyl-1,4,4aa,5,6,7,8,8aa-octahydronaphthalene (13) and isomeric exo olefin 21. The phenol acetate 34, however, was so resistant to oxidation that no corresponding 12-oxo derivative, which was expected to provide 11-acetoxy-12ba-acetoxymethyl-12-oxo-4,4,6aa,9-tetramethyl-1,2,3,4,4aa,5,6,6a,12aa,12b-decahydro-12H-benzo[a]xanthene (4) on epimerization at its C(12a) position as well as hydrofuran ring formation at the C(12) position with its angular methoxymethyl substituent, was obtained.

Acetyl nitronates (acetic nitronic anhydrides), readily obtainable from ketones and nitroalkenes, have been demonstrated to serve as potentially useful intermediates for the synthesis of 2,5-dialkylpyrrolidines and 2,5-dialkylpyrrolines, and a short-step synthesis of some ant venom alkaloids has been accomplished via these acetyl nitronates.

The reported Robinson annelation of 2-methylcyclohexanone with 3-penten-2-one has been reexamined. In contrast to the previous result, it was found that the reaction product was not only obtained in a low yield, but also the solvent-depending stereoselectivity in the formation of cis-4,4a-dimethyl-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one (3a) and its transisomer (3b) was considerably lower than that reported. As expected, regioisomers, 4β,8α-dimethyl-4,4aβ,5,6,7,8-hexahydronaphthalen-2(3H)-one and 4β,8β-dimethyl-4,4aα,5,6,7,8-hexahydronaphthalen-2(3H)-one, were also formed in the annelation. A similar tendency was observed in the reaction with 4-phenyl-3-penten-2-one. The annelation products, 3a, 3b, cis-4-phenyl-4a-methyl-4,4a,5,6,7,8-hexahydronaphthalen-2(3H)-one, and trans-4-phenyl-4a-methyl-4,4a,5,6,7,8-hexahydronaphthalen-2 (3H)-one, were also synthesized by an alternative route.

Curzerenone and epicurzerenone were synthesized by means of a combination of γ-ketoester synthesis and 3-methylfuran annulation both of which utilize nitroolefins as synthons. Starting material, methyl 2-methyl-4-oxo-2-vinylpentanoate, was prepared by the Lewis acid-promoted reaction of l-methoxy-2-methyl-l-[(trimethylsily)oxy]-1,3-butadiene and 2-nitropropene, while key intermediate 3,6-dimethyl-6-vinyl-6,7-dihydrobenzofuran-4(5H)-one was assembled by the KF-catalyzed reaction of 5-methyl-5-vinylcyclohexane-l,3-dione and 1-nitro-1-phenylthiopropene.

Short step synthesis of dehydroisoerivanin, isoerivanin, ludovicin C, and 1α,3α-dihydroxyarbusculin B have been achieved by employing the organoselenium-mediated reduction of α,β-epoxy ketone as the key step.

As a model study for the synthesis of anisatin, 2-oxaspiro[3.5]nonane and 5-hydroxy-5-methyl-2-oxaspiro[3.5]nonane were synthesized from methyl cyclohexanecarboxylate and 2-ethoxycarbonylcyclohexanone, respectively, and these oxetanes were submitted to ruthenium tetroxide oxidation to afford the corresponding β-lactones.

2- (Phenylthio)-2-penten-5-olide, readily accessible from δ-valelolactone, showed high electrophilic reactivities toward some typical carbon nucleophiles to give 3-substituted 2-(phenylthio)pentanolides, which were convertible to a variety of 3-substituted pentan-5-olides and 2-penten-5-olides.

Annulation reaction of α-formylcaprylate (5) with 2,5-dihydro-3-phenylthio-4-vinylfuran-2-one (2), followed by dehydration, oxidation, and rearrangement, provided an epimeric mixture of 2,4,5,6-tetrahydro-6-hexyl-4-hydroxy-6-methoxycarbonylbenzofuran-2-ones (8aand 8b). From both the products, 2,3,3aβ,4,6,6aβ-hexahydro-4β-octylfuro [2,3-c] furan-2,6-dione (4b), the known synthetic precursor of (±)-avenaciolide (1) was obtained.

As a convenient synthetic method of γ-keto acids, oxoalkylation of carboxylic acids with nitroolefins was examined. Carboxylic acid dianions reacted with conjugated nitroolefins at low temperature (−100°C) and a variety of γ-keto acids were obtained on acidic workup in moderate to good yields.

A benzylic hydroxyl group activated by the 2,6-dimethoxy-4-methylphenyl group was proved to be a remarkably reactive nucleofuge in 1,3-diol fragmentation under mild conditions. 4-(2,2,6-Trimethyl-6-vinylcyclohexyl)-2-butanone, a seco-sesquiterpene, was synthesized by using a fragmentation product thereby obtained.

Racemic ligularone and isoligularone were synthesized from 8α,8aα-dimethyl-1,3-dioxo-1,2,3,4,4aα,5,6,7,8,8a-decahydronaphthalene, which was stereoselectively derived from 8aα-methyl-1,6-dioxo-1,2,3,4,4aα,5,6,8a-octahydronaphthalene, using the KF-catalyzed reaction with 1-nitro-1-phenylthiopropene.

The epoxidation of α,β-unsaturated compounds using tetrabutylammonium fluoride is described. This method has been demonstrated to be directly applicable to base-sensitive substrates such as cinnamaldehyde and α-phenylcinnamonitrile.

An efficient route based upon solvolytic fragmentation of a cyclopentadiene-dichloroketene adduct 4chas been investigated for the synthesis of trimethoxyphenylpropyltropolone 2b, a synthetic intermediate of colchicine 1a. Attempted synthesis of the corresponding unsaturated tropolones 8aand 10is also discussed.