Showing papers by "Keiichiro Fukumoto published in 1988"
TL;DR: A highly stereoselective synthesis of the des-A B-aromatic steroid was achieved by an intramolecular cycloaddition of the o-quinodimethane generated in situ from the thermolysis of 3-(1,2-dihydro-4-methoxybenzocyclobutenyl)-1,1-ethylenedioxy-1-isopropenyl-propane.
20 citations
TL;DR: The key synthetic intermediate of 1β-methyl carbapenem antibiotic, (3S, 4R)-3-[(1R)-1-t- butyl-dimethylsiloxyethyl]-4-[(2R)-2-(1-hydroxypropyl)]azetidin-2-one (2), was synthesised from (R)-methyl 3-hydrox-2 -methylpropionate with high stereoselectivity via intramolecular nitrone 1,3-dipolar cycloaddition as mentioned in this paper.
Abstract: The key synthetic intermediate of 1β-methylcarbapenem antibiotic, (–)-(3S, 4R)-3-[(1R)-1-t- butyl-dimethylsiloxyethyl]-4-[(2R)-2-(1-hydroxypropyl)]azetidin-2-one (2), was synthesised from (R)-methyl 3-hydroxy-2-methylpropionate with high stereoselectivity via intramolecular nitrone 1,3-dipolar cycloaddition.
16 citations
TL;DR: In this paper, a double Michael reaction of the α,β-unsaturated enone ester (5) using lithium hexamethyldisilazide produced the tricyclo[5.2.1] undecane derivative (4) in a highly stereoselective manner.
Abstract: Intramolecular double Michael reaction of the α,β-unsaturated enone ester (5) using lithium hexamethyldisilazide produced the tricyclo[5.2.2.01,5] undecane derivative (4) in a highly stereoselective manner. The annulation of (5) was further investigated under various conditions. The tricyclic compound (4) was converted into the tetracyclo[7.3.1.04,12.05,13]tridecane derivative (31), the CDF part of Aconitum alkaloids, via a Wagner–Meerwein-type rearrangement.
13 citations
TL;DR: The angular triquinane sesquiterpenes, (±)-pentalenene (1), pentalenic acid (2), and deoxypentalenic acids (4), were synthesized via the intramolecular double Michael reaction as the key step as discussed by the authors.
Abstract: The angular triquinane sesquiterpenes, (±)-pentalenene (1), (±)-pentalenic acid (2), and (±)-deoxypentalenic acid (4), were synthesized via the intramolecular double Michael reaction as the key step. Heating the bis-enone (10), prepared from 4,4-dimethylcyclopent-2-enone (11) in six steps, with chlorotrimethylsilane, triethylamine, and zinc chloride gave the tricyclo[7.3.0.0]dodecanedione (9), which was converted into the above triquinanes after ring contraction.
12 citations
TL;DR: Diastereofacial selection has been shown to occur in the asymmetric intramolecular Diels-Alder reactions of chiral o-quinodimethanes generated by thermal ring-opening of the chiral benzocyclobutenes as discussed by the authors.
Abstract: Diastereofacial selection has been shown to occur in the asymmetric intramolecular Diels–Alder reactions of chiral o-quinodimethanes generated by thermal ring-opening of the chiral benzocyclobutenes (1a,b,e,f).
8 citations
TL;DR: In this paper, a novel and efficient synthesis of trans-2,3,3a,4,5,9b-hexahydro-3α-hydroxy-3β-(2-hydroxacetyl)-7-methoxy-3aβ-methyl-1H-benz[e]indene was described.
Abstract: A novel and efficient synthesis of trans-2,3,3a,4,5,9b-hexahydro-3α-hydroxy-3β-(2-hydroxyacetyl)-7-methoxy-3aβ-methyl-1H-benz[e]indene (10) starting from trans-2,3,3a,4,5,9b-hexahydro-3β-isopropenyl-7-methoxy-3α-methoxymethoxy-3aβ-methyl-1H-benz[e]indene (5) and its conversion into 2′,2′,3a-trimethyl-7-oxo-2,3,3a,4,5,6,7,8,9,9b-decahydro-1H-benz[e]indene-3-spiro-4′-(1,3-dioxan)-5′-yl acetate (14) are described.
1 citations
TL;DR: In this article, 1-alkenylbenzocyclobutenyl-1-carboxylic acid was used to obtain 4-alkylideneisochromosochroman-3-ones in good yields via an unprecedented tandem electrocyclic [1,5]sigmatropic process of o-quinodimethane.
Abstract: Thermolysis of 1-alkenylbenzocyclobutenyl-1-carboxylic acid produced 4-alkylideneisochroman-3-ones in good yields via an unprecedented tandem electrocyclic-[1,5]sigmatropic process of o-quinodimethane. Alternatively, thermolysis of the corresponding methyl ester afforded the dihydronaphthalenes via E-transition state in excellent yields.
TL;DR: A new construction of the estrane ring system was achieved by intramolecular double Michael reaction of the α,β-unsaturated enone ester (5) as discussed by the authors, which is the first construction of a ring system in the literature.
Abstract: A new construction of the estrane ring system was achieved by intramolecular double Michael reaction of the α,β-unsaturated enone ester (5).
TL;DR: The first total synthesis of the Calabar bean alkaloid geneserine (1) starting with 1-cyano-5methoxybenzocyclobutene (7) has been accomplished via a 16-step sequence in 27% overall yield as mentioned in this paper.
Abstract: The first total synthesis of the Calabar bean alkaloid geneserine (1) starting with 1-cyano-5-methoxybenzocyclobutene (7) has been accomplished via a 16-step sequence in 27% overall yield. The key step in the synthetic strategy involves the tandem electrocyclic [3,3]sigmatropic reaction of the o-quinodimethane generated in situ by thermolysis of the benzocyclobutene (4), which affords quantitatively the isochroman-3-one (5). After the conversion of (5) into the oxindole (6), the pivotal intermediate for our strategy, differential functionalisation of this system provides the hydroxylamine (19) which has finally been converted into (±)-geneserine by treatment with di-isobutylaluminium hydride.
TL;DR: In this paper, a novel and efficient synthesis of trans-2,3,3a,4,5,9b-hexahydro-3α-hydroxy-3β-(2-hydroxacetyl)-7-methoxy-3aβ-methyl-1H-benz[e]indene was described.
Abstract: A novel and efficient synthesis of trans-2,3,3a,4,5,9b-hexahydro-3α-hydroxy-3β-(2-hydroxyacetyl)-7-methoxy-3aβ-methyl-1H-benz[e]indene (10) starting from trans-2,3,3a,4,5,9b-hexahydro-3β-isopropenyl-7-methoxy-3α-methoxymethoxy-3aβ-methyl-1H-benz[e]indene (5) and its conversion into 2′,2′,3a-trimethyl-7-oxo-2,3,3a,4,5,6,7,8,9,9b-decahydro-1H-benz[e]indene-3-spiro-4′-(1,3-dioxan)-5′-yl acetate (14) are described.
TL;DR: In this paper, a preferential electrocyclic reaction of o-quinodimethanes generated by the thermolysis of 1-alkyl-1-alkenylbenzocyclobutenes was proposed.
Abstract: Substituted dihydronaphthalenes and naphthalenes are obtained via a preferential electrocyclic reaction of o-quinodimethanes generated by the thermolysis of 1-alkyl-1-alkenylbenzocyclobutenes.
TL;DR: The key synthetic intermediate of 1β-methyl carbapenem antibiotic, (3S, 4R)-3-[(1R)-1-t- butyl-dimethylsiloxyethyl]-4-[(2R)-2-(1-hydroxypropyl)]azetidin-2-one (2), was synthesised from (R)-methyl 3-hydrox-2 -methylpropionate with high stereoselectivity via intramolecular nitrone 1,3-dipolar cycloaddition as discussed by the authors.
Abstract: The key synthetic intermediate of 1β-methylcarbapenem antibiotic, (–)-(3S, 4R)-3-[(1R)-1-t- butyl-dimethylsiloxyethyl]-4-[(2R)-2-(1-hydroxypropyl)]azetidin-2-one (2), was synthesised from (R)-methyl 3-hydroxy-2-methylpropionate with high stereoselectivity via intramolecular nitrone 1,3-dipolar cycloaddition.
TL;DR: In this paper, the Wagner-Meerwein-type rearrangement of the mesylated precursor was used to transform the ester to the product via a Wagner-meersch-wein approach.
Abstract: The title reaction of the ester (II) yields the derivative (III), which is transformed to the product (VIII) via a Wagner-Meerwein-type rearrangement of the mesylated precursor (VI).