Showing papers by "Keiichiro Fukumoto published in 1996"
33 citations
TL;DR: In this article, 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.
22 citations
TL;DR: In this paper, an enantioselective total synthetic route to (+)-pumiliotoxin C (1) has been described, using the chirally homogeneous cyclohexenol 3.
18 citations
TL;DR: In this article, a stereoselective formal synthesis of the diterpene tetraol (+)-aphidicolin is described employing as key steps the cycloisomerization of the enyne 9 to provide the bicyclo[3.2] octane derivative 8 and the intramolecular Diels-Alder reaction of the triene 7 to form the aphidicolane-type ring system.
15 citations
TL;DR: In this paper, the complete stereocontrolled synthesis of angularly disubstituted cis-decalins based on the sequenced radical ring expansion and cyclization process of α-iodomethylcyclopentanones 1 and 6 is described and the stereochemical outcome of this radical reaction is also discussed.
5 citations
TL;DR: Simple and highly effective methods for the synthesis of polycyclic ring systems via two types of intramolecular domino reactions are developed and presented.
Abstract: Simple and highly effective methods for the synthesis of polycyclic ring systems via two types of intramolecular domino reactions are developed and presented. The first example is an intramolecular double Michael reaction, whose scope-limitation, mechanism and application to natural product synthesis are discussed. The intramolecular Michael-aldol reaction is the second case, which provides a nice method for the preparation of polycyclic compounds having a four-membered ring system. In addition, some related reactions of these methods are described.
3 citations
TL;DR: The iodonium ion mediated ring expansion of the olefinic cyclobutanols 19, 20, and 22 gave the mixture of iodoalkylated cyclopentanones 27a-c and 28a−c, respectively as discussed by the authors.
Abstract: The iodonium ion mediated ring expansion of the olefinic cyclobutanols 19 , 20 , and 22 gave the mixture of iodoalkylated cyclopentanones 27a–c and 28a–c , respectively. On the other hand, the same reaction of 24 – 26 afforded stereoselectively the iodoalkylated cyclopentanones 27d and 27e .
TL;DR: In this paper, a stereoselective formal synthesis of the diterpene tetraol (+)-aphidicolin is described employing as key steps the cycloisomerization of the enyne 9 to provide the bicyclo[3.2] octane derivative 8 and the intramolecular Diels-Alder reaction of the triene 7 to form the aphidicolane-type ring system.
Abstract: Stereoselective formal synthesis of the diterpene tetraol (+)-aphidicolin (1) is described employing as key steps the cycloisomerization of the enyne 9 to provide the bicyclo[3.2.1]octane derivative 8 and the intramolecular Diels-Alder reaction of the triene 7 to form the aphidicolane-type ring system. This route is, in principal, highly stereocontrolled and extremely efficient.
TL;DR: In this article, 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.
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.
TL;DR: In this paper, the induced diastereoselectivity of the intramolecular Diels-Alder reaction of the trifluoromethyl substituted olefinic o -quinodimethanes 10, 11, and 21 a g, generated in situ by the thermolysis of the corresponding benzocyclobutenes 6, 7, and 20a g respectively, was investigated experimentally and theoretically.
Abstract: The induced diastereoselectivity of the intramolecular Diels-Alder reaction of the trifluoromethyl substituted olefinic o -quinodimethanes 10, 11 , and 21 a – g , generated in situ by the thermolysis of the corresponding benzocyclobutenes 6, 7 , and 20a – g respectively, was investigated experimentally and theoretically. The both cis (ring juncture) and anti selectivity [relative configuration of C 13 and C 17 (steroid numbering) substituents] were enhanced on comparing with that of the corresponding methyl analogs. Semi empirical PM3 calculations have been used to locate the transition structures of the intramolecular Diels-Alder reactions of 10, 11 , and some of 21 . The obtained data were compared with the experimental results of the cycloadditions and showed a good agreement.