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Noritaka Chida - One of the best experts on this subject based on the ideXlab platform.
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synthesis of β hydroxy α α disubstituted amino acids through the orthoamide type Overman Rearrangement of an α β unsaturated ester and stereodivergent intramolecular sn2 reaction development and application to the total synthesis of sphingofungin f
Bulletin of the Chemical Society of Japan, 2018Co-Authors: T Sugai, Takaaki Sato, Takeshi Oishi, Shun Tsuzaki, Shunme Usui, Hiroki Oishi, Daichi Yasushima, Takahiro Fukuyasu, Shoko Hisada, Noritaka ChidaAbstract:The development of a two-step synthesis for β-hydroxy-α,α-disubstituted amino acid derivatives from cyclic orthoamide is reported. The first step is the orthoamide-type Overman Rearrangement of an α,β-unsaturated ester to give a sterically hindered α,α-disubstituted amidoester. The α,β-unsaturated ester is known to be a challenging substrate in the conventional Overman Rearrangement due to the competitive aza-Michael reaction. However, suppression of the aza-Michael reaction is realized by two factors; 1) the high reaction temperature, and 2) an alkyl substituent at the α-position. The second step is stereodivergent intramolecular SN2′ reaction for the installation of a hydroxy group at the β-position. Either syn- or anti-type SN2′ reaction is possible by simply changing the reaction conditions. The developed method can provide all four possible stereoisomers of the β-hydroxy-α,α-disubstituted amino acid, and is successfully applied to the total synthesis of sphingofungin F.
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total synthesis of sphingofungin f by orthoamide type Overman Rearrangement of an unsaturated ester
Organic Letters, 2015Co-Authors: Shun Tsuzaki, Takaaki Sato, Takeshi Oishi, Shunme Usui, Hiroki Oishi, Daichi Yasushima, Takahiro Fukuyasu, Noritaka ChidaAbstract:The total synthesis of sphingofungin F through the Overman Rearrangement of an unsaturated ester, which is known to be an unsuitable substrate under standard conditions due to the competitive aza-Michael reaction, is described. The developed conditions enabled the ester to be compatible with the original Overman Rearrangement, providing quick access to α,α-disubstituted amino acids by minimizing extra protecting group manipulations and redox reactions.
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chirality transfers through sequential sigmatropic Rearrangements of allylic vicinal diols development and application to total synthesis of kainic acid
European Journal of Organic Chemistry, 2012Co-Authors: Katsunori Kitamoto, Takaaki Sato, Yasuaki Nakayama, Mana Sampei, Masato Ichiki, Naoya Furuya, Noritaka ChidaAbstract:A detailed description is presented of two sequential sigmatropic Rearrangements starting from enantiopure allylic vicinal diols. Starting from the same allylic diol, the sequential Claisen/Claisen Rearrangement can install two identical functional groups in a one-pot reaction, whereas, the sequential Claisen/Overman Rearrangement can introduce two different functional groups, both occurring without protecting group manipulation. Both sequential reactions proceeded with complete stereoselectivity, which was easily predictable by the judicious choice of two factors regarding the allylic diols: (1) the stereochemistry of the hydroxy groups and (2) the geometry of the olefin. To demonstrate this sequential Rearrangement methodology, we accomplished the total synthesis of (–)-kainic acid, whose three contiguous stereocenters were completely established by three chirality transfer reactions (SN2′ and sequential Claisen/Overman reactions) of flexible acyclic intermediates derived from D-arabinose.
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total synthesis of broussonetine f the orthoamide Overman Rearrangement of an allylic diol
Organic Letters, 2011Co-Authors: Naoto Hama, Takaaki Sato, Toshihiro Aoki, Shohei Miwa, Miki Yamazaki, Noritaka ChidaAbstract:A first total synthesis of broussonetine F from diethyl l-tartrate was achieved. The cornerstone of our synthesis was an orthoamide Overman Rearrangement, which provided an allylic amino alcohol with complete diastereoselectivity.
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total synthesis of salinosporamide a
Chemistry-an Asian Journal, 2011Co-Authors: Yuji Kaiya, Takayuki Momose, Jun Ichi Hasegawa, Takaaki Sato, Noritaka ChidaAbstract:A detailed description of our second-generation total synthesis of salinosporamide A is presented. Three contiguous stereocenters in the γ-lactam structure seen in the natural product were established by stereoselective functionalization of a D-arabinose scaffold, including an Overman Rearrangement to generate a highly congested tetrasubstituted carbon center. One of the definitive reactions in the synthesis was a Lewis acid mediated skeletal Rearrangement of a pyranose structure, which enabled the practical conversion of the carbohydrate scaffold to the γ-lactam structure embedded in salinosporamide A. The use of a benzyl ester as a protective group for a sterically hindered carboxylic acid led to a one-pot global deprotection at the end of the synthesis.
Andrew Sutherland - One of the best experts on this subject based on the ideXlab platform.
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structural diversification of the aminobicyclo 4 3 0 nonane skeleton using alkynylsilyl derived allylic trichloroacetimidates
Organic and Biomolecular Chemistry, 2017Co-Authors: Mohamed A B Mostafa, Angus Erland Mcmillan, Andrew SutherlandAbstract:The amino substituted bicyclo[4.3.0]nonane is a molecular scaffold found in a wide range of natural products and medicinal agents. Despite this, synthetic methods for the general preparation of this structural motif are sparse. Here we evaluate a diastereoselective approach for the preparation of vinylsilyl derived aminobicyclo[4.3.0]nonanes using a one-pot multi-bond forming process involving a Pd(ii)-catalysed Overman Rearrangement, a Ru(ii)-catalysed ring closing enyne metathesis reaction, followed by a hydrogen bonding directed Diels-Alder reaction. We show that a benzyldimethylsilyl-substituted alkene analogue is amenable to further functionalisation and the late stage generation of diverse sp3-rich, drug-like aminobicyclo[4.3.0]nonane scaffolds with up to six stereogenic centres.
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Synthesis of Allylic Amide Functionalized 2H-Chromenes and Coumarins Using a One-Pot Overman Rearrangement and Gold(I)-Catalyzed Hydroarylation
The Journal of organic chemistry, 2016Co-Authors: Salaheddin A. I. Sharif, Alexander H. Harkiss, Ewen D. D. Calder, Marie Maduro, Andrew SutherlandAbstract:A four-step synthesis of allylic trichloroacetimidates bearing a 2-proparyloxyaryl group has been developed from readily available 2-hydroxybenzaldehydes, and these have been used for the preparation of allylic amide derived 2H-chromenes using an Overman Rearrangement and a 6-endo-dig hydroarylation. High yields of the 2H-chromenes were achieved using a stepwise approach involving an Overman Rearrangement under thermal conditions followed by a hydroarylation reaction with a gold(I) triflimide catalyst. An alternative method where both reactions were performed as a one-pot process was also developed and instead used a gold(I) chloride catalyst activated by silver(I) hexafluoroantimonate for the cycloisomerization step. The allylic amide derived 2H-chromenes were converted to the corresponding coumarin analogues by a pyridinium dichromate (PDC)-mediated chemoselective allylic oxidation.
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Synthesis of Allylic Amide Functionalized 2H‑Chromenes and Coumarins Using a One-Pot Overman Rearrangement and Gold(I)-Catalyzed Hydroarylation
2016Co-Authors: Salaheddin A. I. Sharif, Ewen D. D. Calder, Alexander H. Harkiss, Marie Maduro, Andrew SutherlandAbstract:A four-step synthesis of allylic trichloroacetimidates bearing a 2-proparyloxyaryl group has been developed from readily available 2-hydroxybenzaldehydes, and these have been used for the preparation of allylic amide derived 2H-chromenes using an Overman Rearrangement and a 6-endo-dig hydroarylation. High yields of the 2H-chromenes were achieved using a stepwise approach involving an Overman Rearrangement under thermal conditions followed by a hydroarylation reaction with a gold(I) triflimide catalyst. An alternative method where both reactions were performed as a one-pot process was also developed and instead used a gold(I) chloride catalyst activated by silver(I) hexafluoroantimonate for the cycloisomerization step. The allylic amide derived 2H-chromenes were converted to the corresponding coumarin analogues by a pyridinium dichromate (PDC)-mediated chemoselective allylic oxidation
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preparation of anti vicinal amino alcohols asymmetric synthesis of d erythro sphinganine spisulosine and d ribo phytosphingosine
ChemInform, 2013Co-Authors: Ewen D. D. Calder, Ahmed M Zaed, Andrew SutherlandAbstract:Two protocols for the Overman Rearrangement are developed which allow the synthesis of anti-vicinal amino alcohols [cf.
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preparation of anti vicinal amino alcohols asymmetric synthesis of d erythro sphinganine spisulosine and d ribo phytosphingosine
Journal of Organic Chemistry, 2013Co-Authors: Ewen D. D. Calder, Ahmed M Zaed, Andrew SutherlandAbstract:Two variations of the Overman Rearrangement have been developed for the highly selective synthesis of anti-vicinal amino alcohol natural products. A MOM ether-directed palladium(II)-catalyzed Rearrangement of an allylic trichloroacetimidate was used as the key step for the preparation of the protein kinase C inhibitor d-erythro-sphinganine and the antitumor agent (+)-spisulosine, whereas the Overman Rearrangement of chiral allylic trichloroacetimidates generated by the asymmetric reduction of an α,β-unsaturated methyl ketone allowed rapid access both to d-ribo-phytosphingosine and l-arabino-phytosphingosine.
Christopher J T Hyland - One of the best experts on this subject based on the ideXlab platform.
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synthesis of nitrogen substituted methylenecyclopropanes by strain driven Overman Rearrangement of cyclopropenylmethyl trichloroacetimidates
ChemInform, 2014Co-Authors: James K Howard, Chintan Amin, Brendan C Lainhart, Jason A Smith, Jack Rimington, Christopher J T HylandAbstract:A one-pot sequence of imidate formation followed by Overman Rearrangement allows for preparation of nitrogen-substituted methylenecyclopropanes (MCPs) from known cyclopropenyl carbinols.
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synthesis of nitrogen substituted methylenecyclopropanes by strain driven Overman Rearrangement of cyclopropenylmethyl trichloroacetimidates
Journal of Organic Chemistry, 2014Co-Authors: James K Howard, Chintan Amin, Brendan C Lainhart, Jason A Smith, Jack Rimington, Christopher J T HylandAbstract:Nitrogen-substituted methylenecyclopropanes have been prepared by a strain-driven Overman Rearrangement of cyclopropenylmethyl trichloroacetimidates. The reaction proceeds at room temperature and without the need of a transition-metal catalyst. Furthermore, it has been shown that C-3-substituted cyclopropenylmethyl trichloroacetimidates undergo a hydrolytic ring-opening reaction to form allenylcarbinols.
Takaaki Sato - One of the best experts on this subject based on the ideXlab platform.
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synthesis of β hydroxy α α disubstituted amino acids through the orthoamide type Overman Rearrangement of an α β unsaturated ester and stereodivergent intramolecular sn2 reaction development and application to the total synthesis of sphingofungin f
Bulletin of the Chemical Society of Japan, 2018Co-Authors: T Sugai, Takaaki Sato, Takeshi Oishi, Shun Tsuzaki, Shunme Usui, Hiroki Oishi, Daichi Yasushima, Takahiro Fukuyasu, Shoko Hisada, Noritaka ChidaAbstract:The development of a two-step synthesis for β-hydroxy-α,α-disubstituted amino acid derivatives from cyclic orthoamide is reported. The first step is the orthoamide-type Overman Rearrangement of an α,β-unsaturated ester to give a sterically hindered α,α-disubstituted amidoester. The α,β-unsaturated ester is known to be a challenging substrate in the conventional Overman Rearrangement due to the competitive aza-Michael reaction. However, suppression of the aza-Michael reaction is realized by two factors; 1) the high reaction temperature, and 2) an alkyl substituent at the α-position. The second step is stereodivergent intramolecular SN2′ reaction for the installation of a hydroxy group at the β-position. Either syn- or anti-type SN2′ reaction is possible by simply changing the reaction conditions. The developed method can provide all four possible stereoisomers of the β-hydroxy-α,α-disubstituted amino acid, and is successfully applied to the total synthesis of sphingofungin F.
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total synthesis of sphingofungin f by orthoamide type Overman Rearrangement of an unsaturated ester
Organic Letters, 2015Co-Authors: Shun Tsuzaki, Takaaki Sato, Takeshi Oishi, Shunme Usui, Hiroki Oishi, Daichi Yasushima, Takahiro Fukuyasu, Noritaka ChidaAbstract:The total synthesis of sphingofungin F through the Overman Rearrangement of an unsaturated ester, which is known to be an unsuitable substrate under standard conditions due to the competitive aza-Michael reaction, is described. The developed conditions enabled the ester to be compatible with the original Overman Rearrangement, providing quick access to α,α-disubstituted amino acids by minimizing extra protecting group manipulations and redox reactions.
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chirality transfers through sequential sigmatropic Rearrangements of allylic vicinal diols development and application to total synthesis of kainic acid
European Journal of Organic Chemistry, 2012Co-Authors: Katsunori Kitamoto, Takaaki Sato, Yasuaki Nakayama, Mana Sampei, Masato Ichiki, Naoya Furuya, Noritaka ChidaAbstract:A detailed description is presented of two sequential sigmatropic Rearrangements starting from enantiopure allylic vicinal diols. Starting from the same allylic diol, the sequential Claisen/Claisen Rearrangement can install two identical functional groups in a one-pot reaction, whereas, the sequential Claisen/Overman Rearrangement can introduce two different functional groups, both occurring without protecting group manipulation. Both sequential reactions proceeded with complete stereoselectivity, which was easily predictable by the judicious choice of two factors regarding the allylic diols: (1) the stereochemistry of the hydroxy groups and (2) the geometry of the olefin. To demonstrate this sequential Rearrangement methodology, we accomplished the total synthesis of (–)-kainic acid, whose three contiguous stereocenters were completely established by three chirality transfer reactions (SN2′ and sequential Claisen/Overman reactions) of flexible acyclic intermediates derived from D-arabinose.
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total synthesis of broussonetine f the orthoamide Overman Rearrangement of an allylic diol
Organic Letters, 2011Co-Authors: Naoto Hama, Takaaki Sato, Toshihiro Aoki, Shohei Miwa, Miki Yamazaki, Noritaka ChidaAbstract:A first total synthesis of broussonetine F from diethyl l-tartrate was achieved. The cornerstone of our synthesis was an orthoamide Overman Rearrangement, which provided an allylic amino alcohol with complete diastereoselectivity.
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total synthesis of salinosporamide a
Chemistry-an Asian Journal, 2011Co-Authors: Yuji Kaiya, Takayuki Momose, Jun Ichi Hasegawa, Takaaki Sato, Noritaka ChidaAbstract:A detailed description of our second-generation total synthesis of salinosporamide A is presented. Three contiguous stereocenters in the γ-lactam structure seen in the natural product were established by stereoselective functionalization of a D-arabinose scaffold, including an Overman Rearrangement to generate a highly congested tetrasubstituted carbon center. One of the definitive reactions in the synthesis was a Lewis acid mediated skeletal Rearrangement of a pyranose structure, which enabled the practical conversion of the carbohydrate scaffold to the γ-lactam structure embedded in salinosporamide A. The use of a benzyl ester as a protective group for a sterically hindered carboxylic acid led to a one-pot global deprotection at the end of the synthesis.
Brian M. Stoltz - One of the best experts on this subject based on the ideXlab platform.
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Stereospecific Overman Rearrangement of Substituted Cyclic Vinyl Bromides: Access to Fully Substituted α-Amino Ketones.
Organic letters, 2019Co-Authors: Álvaro Velasco-rubio, Eric J. Alexy, Makoto Yoritate, Austin C. Wright, Brian M. StoltzAbstract:A versatile thermal Overman Rearrangement of enantioenriched, cyclic allylic alcohols providing tertiary allylic amines has been developed. The vinyl bromide used to control enantioselectivity in a...
