Showing papers by "Keiichiro Fukumoto published in 1989"
TL;DR: In this article, the synthesis of the key intermediate of the 1β-methyl carbapenem antibiotic was investigated by way of inter-and intramolecular nitrone 1,3-dipolar cycloaddition.
Abstract: Synthesis of the key intermediate of the 1β-methylcarbapenem antibiotic (1) was investigated by way of inter- and intramolecular nitrone 1,3-dipolar cycloaddition. A highly enantioselective construction of (3S,4R)-(–-)-3-[(1R)-1-(t-butyldimethylsiloxy)ethyl]-4-[(1R)-1-(hydroxymethyl)ethyl]azetidin-2-one (2) was achieved via intramolecular cycloaddition of the nitrone (6).
20 citations
TL;DR: In this paper, the synthesis of chiral intermediates having one tertiary asymmetric center was carried out via chiral half-esters of monoalkylmalonic acids, and enantioselective preparation of unsymmetrical propane-1,3-diol derivatives was achieved by the use of 8-phenylmenthyl half-ester.
Abstract: Syntheses of chiral intermediates having one tertiary asymmetric centre were carried out via chiral half-esters of monoalkylmalonic acids. The menthyl half-ester of ethylmalonic acid afforded a single diastereoisomer through crystallisation-induced asymmetric transformation (second-order asymmetric transformation). Furthermore enantioselective preparation of unsymmetrical propane-1,3-diol derivatives was achieved by the use of 8-phenylmenthyl half-esters.
19 citations
TL;DR: A substituent effect on the diastereoselectivity of an Intramolecular Diels–Alder reaction of o-quinodimethanes has been studied and a highly diasterenoselective synthesis of trans-benzoperhydrindan has been achieved.
Abstract: A substituent effect on the diastereoselectivity of an Intramolecular Diels–Alder reaction of o-quinodimethanes has been studied and a highly diastereoselective synthesis of trans-benzoperhydrindan, which is a key intermediate for the synthesis of steroids, has been achieved by the thermolysis of 2-[2-(1,2-dihydro-4-methoxybenzocyclobuten-1-yl)ethyl]-2-isopropenyl-1,3-dioxolane, followed by acid hydrolysis of the initial product in quantitative yield. trans-Benzoperhydrindan was subsequently converted into (±)-estrone and (+)-adrenosterone.
19 citations
TL;DR: In this paper, the 1-carbomethoxy-1-alkenyloxybenzocyclobutenes were converted to 2-naphthol by sequential dehydrogenation and deprotection.
16 citations
10 citations
TL;DR: The first construction of the estrane ring system was achieved by the Intramolecular double Michael reaction as the key step as discussed by the authors, which was achieved through the extraction of the α,β-unsaturated enone ester from the optically active indanone.
Abstract: Construction of the estrane ring system was achieved by the Intramolecular double Michael reaction as the key step. Heating of the α,β-unsaturated enone ester (18), prepared from the optically active indanone (4), with chlorotrimethylsilane, triethylamine, and zinc chloride produced three estrane derivatives (19), (22), and (25).
7 citations
TL;DR: In this article, a highly stereoselective synthesis of the des-A B-aromatic steroid (3) 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 (2).
Abstract: A highly stereoselective synthesis of the des-A B-aromatic steroid (3) 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 (2). Then, compound (3) was converted into (±)-estrone (12) and (±)-adrenosterone (21).
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 mentioned in this paper.
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.
TL;DR: The first construction of the estrane ring system was achieved by the Intramolecular double Michael reaction as the key step as discussed by the authors, which was achieved through the extraction of the α,β-unsaturated enone ester from the optically active indanone.
Abstract: Construction of the estrane ring system was achieved by the Intramolecular double Michael reaction as the key step. Heating of the α,β-unsaturated enone ester (18), prepared from the optically active indanone (4), with chlorotrimethylsilane, triethylamine, and zinc chloride produced three estrane derivatives (19), (22), and (25).
TL;DR: In this article, the synthesis of chiral intermediates having one tertiary asymmetric center was carried out via chiral half-esters of monoalkylmalonic acids, and enantioselective preparation of unsymmetrical propane-1,3-diol derivatives was achieved by the use of 8-phenylmenthyl half-ester.
Abstract: Syntheses of chiral intermediates having one tertiary asymmetric centre were carried out via chiral half-esters of monoalkylmalonic acids. The menthyl half-ester of ethylmalonic acid afforded a single diastereoisomer through crystallisation-induced asymmetric transformation (second-order asymmetric transformation). Furthermore enantioselective preparation of unsymmetrical propane-1,3-diol derivatives was achieved by the use of 8-phenylmenthyl half-esters.
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.
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).
TL;DR: In this article, a substituent effect on the diastereoselectivity of an Intramolecular Diels-Alder reaction of o-quinodimethanes has been studied and trans-benzoperhydrindan, which is a key intermediate for the synthesis of steroids, has been achieved by the thermolysis of 2-[2-(1,2-dihydro-4-methoxybenzocyclobuten-1-yl)ethyl]-2-isopropenyl-1,3-d
Abstract: A substituent effect on the diastereoselectivity of an Intramolecular Diels–Alder reaction of o-quinodimethanes has been studied and a highly diastereoselective synthesis of trans-benzoperhydrindan, which is a key intermediate for the synthesis of steroids, has been achieved by the thermolysis of 2-[2-(1,2-dihydro-4-methoxybenzocyclobuten-1-yl)ethyl]-2-isopropenyl-1,3-dioxolane, followed by acid hydrolysis of the initial product in quantitative yield. trans-Benzoperhydrindan was subsequently converted into (±)-estrone and (+)-adrenosterone.