Hideo Nemoto

A novel o-quinodimethane strategy for an active metabolite of vitamin D3. A total synthesis of 25-hydroxy windaus-grundmann ketone

Abstract A highly diastereoselective total synthesis of 25-hydroxy Windaus-Grundmann ketone (2) was achieved via a novel regiocontrolled CC bond formation by an intramolecular epoxide ring opening reaction of the bissulfonyl epoxide (19) as a key step, which was derived stereoselectively by the thermolysis of olefinic benzocyclobutene (8) as a key step.

Palladium-catalyzed cascade ring expansion reaction of 1-(3-methoxycarbonyloxy-1-propynyl)cyclobutanols with phenols

Abstract A palladium-catalyzed transformation of 1-(3-methoxycarbonyloxy-1-propynyl)cyclobutanols to cyclo-pentanones on treatment with phenol derivatives is described. This process can be visualized to proceed via nucleophilic attack to allenyl palladium species by phenol, followed by ring expansion reaction of π-allylpalladium complex to form the corresponding cyclopentanone.

A novel and efficient route to chiral A-ring aromatic trichothecanes—The first enantiocontrolled total synthesis of (-)-debromofiliformin and (-)-filiformin

Abstract The first examples of asymmetric dihydroxylation (AD) of the cyclopropylidene derivatives 12a∼e followed by enantiospecific 1,2-rearrangement of the resulted diols 13a∼e to give the optically active cyclobutanones 15a∼d and 11, and also the first enantiocontrolled total synthesis of (-)-debromofiliformin (7a) and (-)-filiformin (7b) starting from 11 via the regiocontrolled cyclization of the phenolic allyl alcohol 25 to the A-ring aromatic trichothecane 26, were reported.

A novel strategy for the enantioselective synthesis of the steroidal framework using cascade ring expansion reactions of small ring systems-asymmetric total synthesis of (+)-equilenin

Abstract Enantioselective synthesis of (+)-equilenin ( 1 ) utilizing a novel strategy is described. The key steps are two cascade ring expansion reactions of small ring systems; 1) chiral (salen)Mn III complex-catalyzed cascade reaction of cyclopropylidene; 2) Pd II -mediated cascade reaction of the cyclobutanol.

Total synthesis of (±)-4-deoxyverrucarol; a new route to trichothecanes via ring expansion of small ring compounds

Abstract Total synthesis of 4-deoxyverrucarol ( 4 ), a trichothecane-type sesquiterpene was achieved via two types of ring expansion reaction, 1,2-rearrangement of 18 and palladium mediated ring expansion reaction of 20 , as key steps providing a new route to trichothecanes.

Studies on the stereochemical course of intramolecular cycloaddition reactions of olefinic o-quinodimethanes-stereoselective synthesis of 8α, 9α, 14β-estranes

Abstract The stereoselective synthesis of 3-O-methyl-7α- p -toluenesulphonyl-8α, 9α, 14β-estradiol ( 25 ) and its 11-oxo derivative ( 26 ) via thermolysis of 1β- tert -butoxy-2α-[2-(4-methoxybenzocyclobutenyl)ethyl]-2β-methy1-3α-[2-( p -toluenesulphonyl)ethenyl] cyclopentane ( 22 ) and its oxo derivative ( 24 ), which were derived from condensation product ( 9 ) of optically active aldehyde ( 8 ) and 1-cyano-4-methoxybenzocyclobutene through 10 and 11 to selenides 16 and 21 , is described.

A novel and general route to diverse A-ring aromatic trichothecanes via cyclobutanes

Abstract A novel and generally applicable approach to A-ring aromatic trichothecane 2 was achieved by the regiocontrolled cyclization of 25, 26, 29 , and 30 as a key step, followed by stereoselective construction of the epoxide ring. This manuscript also described the regiocontrolled ring expansion of the olefinic cyclobutanols 19–22 to give the enones 23 and 24 which were the important intermediates in this approach.

The first example of asymmetric dihydroxylation of cyclopropylidene derivatives—An enantioenriched formal total synthesis of (−)-filiformin

Abstract The first example of asymmetric dihydroxylation (AD) of the cyclopropylidene derivatives 4a∼e followed by enantiospecific 1,2-rearrangement of the resulted diols 5a∼e to give the optically active cyclobutanones 7∼e was reported. The synthesis of 7e constitutes an enantioenriched formal total synthesis of (−)-filiformin (8).

An asymmetric synthesis of benzylic quaternary carbon centers. A formal total synthesis of (−)-mesembrine

Abstract The optically pure sulfone 15, prepared by the tandem asymmetric epoxidation and 1,2-rearrangement of the cyclopropylideneethanol 11 as a key step, was converted into the olefinic cyclobutanone 20 which was then transformed into the ketonic lactone 22 via the olefinic lactone 21. This constitutes the formal total synthesis of (−)-mesembrine (1).

A concise enantiocontrolled total synthesis of (-)-α-bisabolol and (+)-4-epi-α-bisabolol

Abstract The regiocontrolled hydrogenation of the cyclohexadiene 6, synthesised from the chiral cyclobutanone 3 was effectively achieved with [1,4-bis(diphenylphosphino)butane](1,5-cyclooctadiene)rhodium (1) tetrafluoroborate as catalyst to give the olefins 7 and 8 which were converted into (−)-α-bisabolol 1a and (+)-4-epi-α-bisabolol 15via9 and 10, 11 and 12, and 13 and 14.