Kennosuke Itoh

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We describe examples of highly regio- and enantioselective nitrile oxide cycloadditions to unsaturated alkenes using substoichiometric amounts of a chiral Lewis acid. Pyrazolidinones proved to be effective achiral templates in the cycloadditions providing C-adducts typically in >30:1 selectivity and 80-99% ee. To avoid potential problems involving(More)
Highly enantioselective 1,3-dipolar cycloaddition reactions, catalyzed by chiral Lewis acids, between several 3-(2-alkenoyl)-2-oxazolidinones and carbonyl ylides that were generated from N-diazoacetyl lactams are described. Reactions of N-diazoacetyl lactams that possess 5-, 6-, and 7-membered rings were transformed to the corresponding epoxy-bridged(More)
As the reports about C-homomorphinans with the seven-membered C-ring are much fewer than those of morphinan derivatives with a six-membered C-ring, we attempted to synthesize C-homomorphinan derivatives and to evaluate their opioid activities. C-Homomorphinan 5 showed sufficient binding affinities to the opioid receptors. C-Homomorphinan derivatives(More)
Asymmetric 1,3-dipolar cycloaddition reactions between N-methylindoles and several cyclic carbonyl ylides that were derived from diazodiketone or diazoketoester precursors in the presence of both achiral Rh and chiral lanthanoid metal catalysts are described. For the six-membered cyclic carbonyl ylides derived from 1-diazo-5-aryl-2,5-pentanedione(More)
[reaction: see text] The use of N-H imide templates provides a solution to the problem of rotamer control in Lewis acid catalyzed reactions of alpha,beta-disubstituted acryloyl imides. Reactions proceed through the s-cis rotamer and with improved reactivity because A(1,3) strain is avoided. Enantioselective nitrone, nitrile oxide, and Diels-Alder(More)
Photoexcited nitrones serve as excellent electron acceptors as well as radical acceptors in the presence of tertiary amines to give β-amino hydroxylamines via photochemically-induced direct sp(3) C-H functionalization of the tertiary amines. The combined use of an organophotosensitizer and photoirradiation was highly effective in accelerating addition(More)
[reaction: see text] The reaction of dimedone with 1-(2-alkenoyl)-4-bromo-3,5-dimethylpyrazoles in THF, catalyzed by catalytic amounts of both DBFOX/Ph-nickel(II) perchlorate trihydrate and 2,2,6,6-tetramethylpiperidine, in the presence of acetic anhydride in THF produces the corresponding enol lactones in high enantioselectivities through enantioselective(More)
The alkaline treatment of the pyridinium salts, readily available from the S-alkylations of 3-amino-4-(1-pyridinio)thiophene-5-thiolates with various alkyl halides, in chloroform at room temperature afforded the corresponding thieno[3',4':4,5]imidazo[1,2-a]pyridine derivatives in low to moderate yields via the intramolecular cyclization of the resulting(More)
Buprenorphine shows strong analgesic effects on moderate to severe pain. Although buprenorphine can be used more safely than other opioid analgesics, it has room for improvement in clinical utility. Investigation of compounds structurally related to buprenorphine should be an approach to obtain novel analgesics with safer and improved profiles compared to(More)