Showing papers by "Keiichiro Fukumoto published in 1992"
TL;DR: In this article, a tandem Katsuli-Sharpless asymmetric epoxidation and enantiospecific ring expansion of 2-alkyl(or 2-aryl)-2-cyclopropylideneethanols (1a-i) afforded chiral 1-alky(or 1-aryl)1-(hydroxymethyl)cyclobutanones (3a)-i) in high yields and high enantiomeric excess.
Abstract: A tandem Katsuli-Sharpless asymmetric epoxidation and enantiospecific ring expansion of 2-alkyl(or 2-aryl)-2-cyclopropylideneethanols (1a-i) afforded chiral 1-alkyl(or 1-aryl)-1-(hydroxymethyl)cyclobutanones (3a-i) in high yields and high enantiomeric excess. These compounds are potentially valuable synthons for the enantioselective creation of the quaternary carbons. Hence, this enabled us to accomplish a concise and enantioselective total synthesis of both (+)- and (-)-α-cuparenones
71 citations
TL;DR: Fluorination of methyl (1R,3R,4S)-8-phenylmenthyl methylmalonates using lithium hexamethyl-disilazide and 1-fluoro-2,4,6-trimethylpyridinium triflate (trifluoromethanesulfonate) gave the (R)-3 and (S)-4 isomers in a 3.8 : 1 ratio, while fluorination of ethyl-, propyl- and benzyl-malonsates 10, 11 and 12 provided
Abstract: Fluorination of methyl (1R,3R,4S)-8-phenylmenthyl methylmalonates 2 using lithium hexamethyl-disilazide and 1-fluoro-2,4,6-trimethylpyridinium triflate (trifluoromethanesulfonate), gave the (R)-3 and (S)-4 isomers in a 3.8 : 1 ratio, while fluorination of ethyl-, propyl- and benzyl-malonates 10, 11 and 12 provided the (R)-13, 15 and 17 and (S)-14, 16 and 18 isomers in a 1 : 1.6–2.0 ratio. On the other hand, alkylation of (1R,3R,4S)-8-phenylmenthyl hydrogen fluoromalonates 26 in the presence of lithium hexamethyldisilazide, followed by esterification with diazomethane, produced the (R)-3,13,15,17- and 27 and (S)-4,14,16,18 and 28 isomers in a 1 : 5.7–35 ratio.
24 citations
TL;DR: In this paper, an alternative strategy for preparing 3-acetoxymethyl-2,3-dihydro-1-methylsulfon-yl-6-methoxyindole 25 has been developed.
Abstract: Development of an alternative strategy for preparing 3-acetoxymethyl-2,3-dihydro-1-methylsulfon-yl-6-methoxyindole 25 has been completed. Since 25 was an intermediate in a previous synthesis of the CPl unit 5 of the antitumour antibiotic CC-1065 1, this achievement constitutes a formal synthesis of the racemic compound 5. The key strategic element of the approach involves the tandem Michael addition–[3,3]sigmatropic rearrangement process of methyl propiolate 10 and benzyl N-hydroxy-N-(3-methoxyphenyl)carbamate 9, prepared from m-nitroanisole 19, to furnish indole 8 as the sole product. Subsequent elaboration of compound 8 into indoline 25 was then achieved by applying Cava's technique. The conversion of 25 into 5 was also demonstrated on the basis of the well-established, Wierenga's procedure.
24 citations
TL;DR: In this article, the thermolysis of the optically active alkenic benzocyclobutenes 9a,4,5,9b,tetrahydro-1H-benz[e]indenes 10 and 11 was studied.
Abstract: Enantioselectivity in the thermolysis of the optically active alkenic benzocyclobutenes 9a–g has been studied, resulting in the development of a novel and efficient route to chiral trans-3a,4,5,9b-tetrahydro-1H-benz[e]indenes 10 and 11.
12 citations
TL;DR: In this article, a method for the one-step conversion of carbamates into amides was developed by the action of acyl chlorides and sodium iodide, which can be used for one step conversion.
Abstract: A novel method for the one step conversion of carbamates into amides was developed by the action of acyl chlorides and sodium iodide
10 citations
TL;DR: In this paper, an enantioselective synthesis of a 6-oxygenated atisine derivative was described, based on the intramolecular double Michael reaction of the enone ester derived through the aldehyde 3 from the symmetrical ketone 4.
9 citations
TL;DR: The epimeric mixture of the trans-substituted tetrahydropyran derivatives (1) was transformed to the cis-sub-stitution lactone (6), which was converted into the piperidine (3), the synthetic intermediate of dihydrocinchonine (5a) and dihydricinchonidine (5b), and the synthetic precursor (11) of (±)-dihydroantirhine (4) as mentioned in this paper.
Abstract: The epimeric mixture of the trans-substituted tetrahydropyran derivatives (1) was transformed to the cis-substituted lactone (6), which was converted into the piperidine (3), the synthetic intermediate of dihydrocinchonine (5a) and dihydrocinchonidine (5b), and the synthetic precursor (11) of (±)-dihydroantirhine (4)
2 citations
TL;DR: In this paper, the chiral, α,α-disubstituted ketone 2-hydroxymethyl-2-methylcyclobutanone was developed, leading to an enantioselective total synthesis of (−)-frontalin, an aggregating pheromone of bark beetles.
Abstract: Novel access to the chiral, α,α-disubstituted ketone 2-hydroxymethyl-2-methylcyclobutanone was developed, leading to an enantioselective total synthesis of (–)-frontalin, an aggregating pheromone of bark beetles.
TL;DR: In this article, the thermolysis of the optically active alkenic benzocyclobutenes 9a,4,5,9b,tetrahydro-1H-benz[e]indenes 10 and 11 was studied.
Abstract: Enantioselectivity in the thermolysis of the optically active alkenic benzocyclobutenes 9a–g has been studied, resulting in the development of a novel and efficient route to chiral trans-3a,4,5,9b-tetrahydro-1H-benz[e]indenes 10 and 11.
TL;DR: In this article, an alternative strategy for preparing 3-acetoxymethyl-2,3-dihydro-1-methylsulfon-yl-6-methoxyindole 25 has been developed.
Abstract: Development of an alternative strategy for preparing 3-acetoxymethyl-2,3-dihydro-1-methylsulfon-yl-6-methoxyindole 25 has been completed. Since 25 was an intermediate in a previous synthesis of the CPl unit 5 of the antitumour antibiotic CC-1065 1, this achievement constitutes a formal synthesis of the racemic compound 5. The key strategic element of the approach involves the tandem Michael addition–[3,3]sigmatropic rearrangement process of methyl propiolate 10 and benzyl N-hydroxy-N-(3-methoxyphenyl)carbamate 9, prepared from m-nitroanisole 19, to furnish indole 8 as the sole product. Subsequent elaboration of compound 8 into indoline 25 was then achieved by applying Cava's technique. The conversion of 25 into 5 was also demonstrated on the basis of the well-established, Wierenga's procedure.
TL;DR: In this article, a tandem Katsuli-Sharpless asymmetric epoxidation and enantiospecific ring expansion of 2-alkyl(or 2-aryl)-2-cyclopropylideneethanols (1a-i) afforded chiral 1-alky(or 1-aryl)1-(hydroxymethyl)cyclobutanones (3a)-i) in high yields and high enantiomeric excess.
Abstract: A tandem Katsuli-Sharpless asymmetric epoxidation and enantiospecific ring expansion of 2-alkyl(or 2-aryl)-2-cyclopropylideneethanols (1a-i) afforded chiral 1-alkyl(or 1-aryl)-1-(hydroxymethyl)cyclobutanones (3a-i) in high yields and high enantiomeric excess. These compounds are potentially valuable synthons for the enantioselective creation of the quaternary carbons. Hence, this enabled us to accomplish a concise and enantioselective total synthesis of both (+)- and (-)-α-cuparenones
TL;DR: Fluorination of methyl (1R,3R,4S)-8-phenylmenthyl methylmalonates using lithium hexamethyl-disilazide and 1-fluoro-2,4,6-trimethylpyridinium triflate (trifluoromethanesulfonate) gave the (R)-3 and (S)-4 isomers in a 3.8 : 1 ratio, while fluorination of ethyl-, propyl- and benzyl-malonsates 10, 11 and 12 provided
Abstract: Fluorination of methyl (1R,3R,4S)-8-phenylmenthyl methylmalonates 2 using lithium hexamethyl-disilazide and 1-fluoro-2,4,6-trimethylpyridinium triflate (trifluoromethanesulfonate), gave the (R)-3 and (S)-4 isomers in a 3.8 : 1 ratio, while fluorination of ethyl-, propyl- and benzyl-malonates 10, 11 and 12 provided the (R)-13, 15 and 17 and (S)-14, 16 and 18 isomers in a 1 : 1.6–2.0 ratio. On the other hand, alkylation of (1R,3R,4S)-8-phenylmenthyl hydrogen fluoromalonates 26 in the presence of lithium hexamethyldisilazide, followed by esterification with diazomethane, produced the (R)-3,13,15,17- and 27 and (S)-4,14,16,18 and 28 isomers in a 1 : 5.7–35 ratio.