Showing papers by "Nobuaki Taniguchi published in 1992"
40 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, the conjugated silyl enol ether was converted to the cyclohexene ring by a base-catalysed equilibration, which was then transformed into (1S*,2R*,7R*,9R*)-3-tert-butyldimethylsiloxy-9,12,12-trimethyltricyclo[7.3.0]dodec-3-en-8-one 18a.
Abstract: (1R*,2S*)-2-(2-Oxobut-3-enyl)-1-(1-oxoprop-2-enyl)-1,3,3-trimethylcyclopentane 5 was prepared stereoselectively from 4,4-dimethylcyclopent-2-en-1-one 6 and then converted into the conjugated silyl enol ether 17. Intramolecular cycloaddition of 17, followed by base-catalysed equilibration, provided (1S*,2R*,7R*,9R*)-3-tert-butyldimethylsiloxy-9,12,12-trimethyltricyclo[7.3.0.0]dodec-3-en-8-one 18a, which was transformed, after contraction of the cyclohexene ring, into the synthetic intermediate 32 for (±)-Δ9(12)-capnellene 1.
12 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: In this article, a double Michael-type reaction was developed to synthesize trans-hydroindane from Iµ-Caprolactone, which was transformed into four isomers of methyl 7-methyl-8-oxo-10-(phenylthio)deca-2,9-dienoate.
Abstract: A sulfur-mediated intramolecular double Michael-type reaction stereoselectively producing trans-hydroindanes was developed. Iµ-Caprolactone 3 was transformed into four [(E,E), (E,Z), (Z,E) and (Z,Z)] isomers of methyl 7-methyl-8-oxo-10-(phenylthio)deca-2,9-dienoate (14, 16, 18 and 19). Treatment of these four isomers, 14, 16, 18 and 19, respectively, with tert-butyldimethylsilyl trifluoromethanesulfonate in the presence of triethylamine gave the trans-hydroindane 20 as the main product together, with a small amount of the cis-isomer 22. The annulation was accelerated by the presence of an electron-donating group on the phenylthio group. Substrates 8, 34, 36 and 37, having hydrogen, isopropyl, trimethylsilyl and phenylsulfinyl instead of the sulfenyl group at the 10-position, provided no cyclised product under the same reaction conditions.
7 citations
TL;DR: In this article, a method for the enantioselective construction of a quaternary stereogenic center by tandem acid anhydride formation-intramolecular Michael reaction has been developed; a synthetic intermediate 16 for Aspidosperma indole alkaloids has been prepared by the application of this procedure.
Abstract: A novel method for the enantioselective construction of a quaternary stereogenic centre by tandem acid anhydride formation–intramolecular Michael reaction has been developed; a synthetic intermediate 16 for Hunteria and Aspidosperma indole alkaloids has been prepared by the application of this procedure.
5 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
1 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.