Showing papers by "Keiichiro Fukumoto published in 1994"
TL;DR: In this paper, the optically pure sulfone was converted into the olefinic cyclobutanone, which was then transformed into the ketonic lactone via the oleinic lactone.
22 citations
21 citations
TL;DR: In this article, an efficient formal total synthesis of antiviral and antitumor tetracyclic diterpene aphidicolin has been developed using an intramolecular Heck reaction (3→4 ) and an intramerolecular Diels-Alder reaction (7→8 ) for the key step of the sequence.
19 citations
TL;DR: In this article, a general method for the preparation of chiral propane-1,3-diol derivatives possessing fluorinated quaternary stereogenic centers was established as follows: the diastereoselective alkylation of (1R,3R,4S)-8-phenylmenthyl hydrogen fluoromalonate, followed by the reduction of the resulting carboxylic acids 10, 13 in two steps, provided the alcohols 14, 17.
Abstract: A general method for the preparation of chiral propane-1,3-diol derivatives possessing fluorinated quaternary stereogenic centers was established as follows. The diastereoselective alkylation of (1R,3R,4S)-8-phenylmenthyl hydrogen fluoromalonate 9, followed by the reduction of the resulting carboxylic acids 10 – 13 in two steps, provided the alcohols 14 – 17. After protection of the hydroxyl group with p-methoxybenzyl group, the phenylmenthyl esters 21 – 24 were converted into chiral propane-1,3-diols 25 and 30 – 32 via the acids 29.
11 citations
TL;DR: In this article, a concise and practical route to the enantiomerically pure des-A B-trienic steroid was developed by thermolysis of the optically active alkenic benzocyclobutene 13 obtained by selective nucleophilic addition of isopropenyl group to the chiral epoxide 9 as a key step.
Abstract: A concise and practical route to the enantiomerically pure des-A B-trienic steroid 14 was developed by thermolysis of the optically active alkenic benzocyclobutene 13 obtained by selective nucleophilic addition of isopropenyl group to the chiral epoxide 9 as a key step.
6 citations
TL;DR: This paper showed that trimethylsilyl iodide in the presence of hexamethyldisilazane caused sequential three reactions, ring opening of cyclopropane-Michael-aldol reaction sequence, to provide polycyclic cyclobutane derivatives.
6 citations
TL;DR: Optically active des-A C-13 ethyl steroids 17∼20 have been synthesized by thermolysis of the optically active alkenic benzocyclobutene 14 as a key process as discussed by the authors.
Abstract: Optically active des-A C-13 ethyl steroids 17∼20 have been synthesized by thermolysis of the optically active alkenic benzocyclobutene 14 as a key process.
6 citations
TL;DR: In this article, a trialkylsilyl trifluoromethansulfonate was used to produce cyclopentanes 14a and 20a and cyclohexanes 14b and 20b.
Abstract: Treatment of the α,β-unsaturated esters 1, 6 and 8 with trialkylsilyl trifluoromethanesulfonate in the presence of a tertiary amine gave, via silyl dienol ethers, the corresponding deconjugated esters 3, 7 and 9 as the major products, respectively. Reaction of bis-α,β-unsaturated esters 12a and 12b with a trialkylsilyl trifluoromethansulfonate in the presence of a tertiary amine caused an intramolecular Michael reaction to produce the cyclopentanes 14a and 20a and the cyclohexanes 14b and 20b. Bicyclic compounds 21a and 21b formed by tandem Michael–Dieckmann or intramolecular Diels–Alder reaction were concurrently obtained. The cyclohexane derivative 14b was converted into the racemate of a sesquiterpene, (±)-ricciocarpin A 22.
2 citations
TL;DR: In this paper, catalytic Lewis acid promoted tandem cycloaddition rearrangement processes of trienic esters were reported under thermal (110°C, aluminum catalyst) conditions and afford the highly functionalized oxabicyclo[3.3.1]nonanes.
Abstract: Catalytic Lewis acid promoted tandem [4 + 2]cycloaddition rearrangement processes of the trienic esters (4), (8) and (9) are reported. The novel tandem reactions proceed under thermal (110°C, aluminum catalyst) conditions and afford the highly functionalized oxabicyclo[3.3.1]nonanes (5), (10) and (11), respectively
1 citations
TL;DR: In this paper, a general method for the preparation of chiral propane-1,3-diol derivatives possessing fluorinated quaternary stereogenic centers was established as follows: the diastereoselective alkylation of (1R,3R,4S)-8-phenylmenthyl hydrogen fluoromalonate, followed by the reduction of the resulting carboxylic acids 10, 13 in two steps, provided the alcohols 14, 17.
Abstract: A general method for the preparation of chiral propane-1,3-diol derivatives possessing fluorinated quaternary stereogenic centers was established as follows. The diastereoselective alkylation of (1R,3R,4S)-8-phenylmenthyl hydrogen fluoromalonate 9, followed by the reduction of the resulting carboxylic acids 10 – 13 in two steps, provided the alcohols 14 – 17. After protection of the hydroxyl group with p-methoxybenzyl group, the phenylmenthyl esters 21 – 24 were converted into chiral propane-1,3-diols 25 and 30 – 32 via the acids 29.
TL;DR: In this article, a short synthesis of enantiomerically pure des-AB-trienic steroid was achieved by thermolysis of the optically active alkenic benzocyclobutene 9 obtained by selective nucleophilic addition of an isopropenyl group to the chiral epoxide.
Abstract: A short synthesis of an enantiomerically pure des-AB-trienic steroid 11 has been achieved by thermolysis of the optically active alkenic benzocyclobutene 9 obtained by selective nucleophilic addition of an isopropenyl group to the chiral epoxide 5 as a key step.
TL;DR: This paper showed that trimethylsilyl iodide in the presence of hexamethyldisilazane caused sequential three reactions, ring opening of cyclopropane-Michael-aldol reaction sequence, to provide polycyclic cyclobutane derivatives.
Abstract: Reaction of α,β-unsaturated esters 4 and 11 possessing a cyclopropyl ketone function, with trimethylsilyl iodide in the presence of hexamethyldisilazane caused sequential three reactions, ring opening of cyclopropane-Michael-aldol reaction sequence, to provide polycyclic cyclobutane derivatives 7 and 13 , respectively.
TL;DR: In this paper, a concise and practical route to the enantiomerically pure des-A B-trienic steroid was developed by thermolysis of the optically active alkenic benzocyclobutene 13 obtained by selective nucleophilic addition of isopropenyl group to the chiral epoxide 9 as a key step.
Abstract: A concise and practical route to the enantiomerically pure des-A B-trienic steroid 14 was developed by thermolysis of the optically active alkenic benzocyclobutene 13 obtained by selective nucleophilic addition of isopropenyl group to the chiral epoxide 9 as a key step.