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Mitsuo Sekine - One of the best experts on this subject based on the ideXlab platform.
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unprecedented mild acid catalyzed desilylation of the 2 o tert butyldimethylsilyl Group from chemically synthesized oligoribonucleotide intermediates via neighboring Group participation of the internucleotidic phosphate residue
Journal of the American Chemical Society, 1996Co-Authors: Shunichi Kawahara, Takeshi Wada, Mitsuo SekineAbstract:Hydrolytic removal of the 2‘-Tert-Butyldimethylsilyl (TBDMS) Group from a 2‘-O-TBDMS protected UpU dimer [U(2‘-Si)pU] (1) (Si = TBDMS) and related derivatives under various acidic conditions was studied in detail. First, desilylation of 1 by use of acetic acid was examined. Consequently, we made the unprecedented discovery that cleavage of the 2‘-silyl ether linkage occurred fastest at a very low concentration of acetic acid within the range of 5−10%, depending on the temperature. Formic acid could cleave the silyl ether much faster than acetic acid, but the relationship between the reaction rate and the concentration of acid was different from that of acetic acid. The use of 20−40% formic acid resulted in very effective elimination of the 2‘-TBDMS Group. Moreover, diluted HCl solution (pH 2.0) could cleave the Si−O bond faster than acetic acid at 30 °C. In contrast, the 2‘-silyl Group of the corresponding methylphosphonate derivative [U(2‘-Si)p(Me)U] (3) was much more stable than that of 1. In the case o...
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unprecedented mild acid catalyzed desilylation of the 2 o tert butyldimethylsilyl Group from chemically synthesized oligoribonucleotide intermediates via neighboring Group participation of the internucleotidic phosphate residue
Journal of the American Chemical Society, 1996Co-Authors: Shunichi Kawahara, Takeshi Wada, Mitsuo SekineAbstract:Hydrolytic removal of the 2‘-Tert-Butyldimethylsilyl (TBDMS) Group from a 2‘-O-TBDMS protected UpU dimer [U(2‘-Si)pU] (1) (Si = TBDMS) and related derivatives under various acidic conditions was st...
Shunichi Kawahara - One of the best experts on this subject based on the ideXlab platform.
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unprecedented mild acid catalyzed desilylation of the 2 o tert butyldimethylsilyl Group from chemically synthesized oligoribonucleotide intermediates via neighboring Group participation of the internucleotidic phosphate residue
Journal of the American Chemical Society, 1996Co-Authors: Shunichi Kawahara, Takeshi Wada, Mitsuo SekineAbstract:Hydrolytic removal of the 2‘-Tert-Butyldimethylsilyl (TBDMS) Group from a 2‘-O-TBDMS protected UpU dimer [U(2‘-Si)pU] (1) (Si = TBDMS) and related derivatives under various acidic conditions was studied in detail. First, desilylation of 1 by use of acetic acid was examined. Consequently, we made the unprecedented discovery that cleavage of the 2‘-silyl ether linkage occurred fastest at a very low concentration of acetic acid within the range of 5−10%, depending on the temperature. Formic acid could cleave the silyl ether much faster than acetic acid, but the relationship between the reaction rate and the concentration of acid was different from that of acetic acid. The use of 20−40% formic acid resulted in very effective elimination of the 2‘-TBDMS Group. Moreover, diluted HCl solution (pH 2.0) could cleave the Si−O bond faster than acetic acid at 30 °C. In contrast, the 2‘-silyl Group of the corresponding methylphosphonate derivative [U(2‘-Si)p(Me)U] (3) was much more stable than that of 1. In the case o...
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unprecedented mild acid catalyzed desilylation of the 2 o tert butyldimethylsilyl Group from chemically synthesized oligoribonucleotide intermediates via neighboring Group participation of the internucleotidic phosphate residue
Journal of the American Chemical Society, 1996Co-Authors: Shunichi Kawahara, Takeshi Wada, Mitsuo SekineAbstract:Hydrolytic removal of the 2‘-Tert-Butyldimethylsilyl (TBDMS) Group from a 2‘-O-TBDMS protected UpU dimer [U(2‘-Si)pU] (1) (Si = TBDMS) and related derivatives under various acidic conditions was st...
Eric J Thomas - One of the best experts on this subject based on the ideXlab platform.
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1 5 asymmetric induction in reactions between aldehydes and 4s 5 tert butyldimethylsilyloxy 4 hydroxypent 2 enyl tributyl stannane promoted by tin iv chloride
Journal of The Chemical Society-perkin Transactions 1, 1995Co-Authors: Robert J Maguire, Eric J ThomasAbstract:[(4S)-5-(Tert-Butyldimethylsilyloxy)-4-hydroxypent-2-enyl](tributyl)stannane 18 has been prepared from di-O-isopropylidene-D-mannitol 8. Oxidative cleavage of the mannitol derivative followed by condensation with triethyl phosphonoacetate and reduction gave the alcohol 10 which was converted into the xanthate 11. Deprotection gave the dihydroxy xanthate 12 which was protected as its bis-Tert-Butyldimethylsilyl ether 13. This rearranged on heating in toluene to give the dithiocarbonate 15 which reacted with tributyltin hydride under free radical conditions to give the [(4S)-4,5-bis(Tert-Butyldimethylsilyloxy)pent-2-enyl](tributyl)stannane 16 as an approximately 9:1 mixture of E- and Z-isomers. Deprotection and selective protection of the primary hydroxy Group provided the [(4S)-5-(Tert-Butyldimethylsilyloxy)-4-hydroxypent-2-enyl]stannane 18. As a shorter route, the primary hydroxy Group of the dihydroxy xanthate 12 was protected as its Tert-Butyldimethylsilyl ether 14 which underwent clean rearrangement into the dithiocarbonate 19 when heated in toluene. Reaction with tributyltin hydride under free radical conditions then gave the (5-Tert-Butyldimethylsilyloxy-4-hydroxypent-2-enyl)stannane 18. Treatment of this 4,5-disubstituted pentenylstannane with tin(IV) chloride generated an allyltin trichloride which reacted with aldehydes with excellent 1,5-asymmetric induction to give 1,5-syn-products, e.g. 20, 29–31 and 41. The stereoselectivity of these reactions would appear to be controlled by the 4-hydroxy substituent rather than by the 5-Tert-Butyldimethylsilyl Group. Aspects of the chemistry of these products, in particular their conversion into 2,6-disubstituted 5,6-dihydro-2H-pyrans, was investigated.
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1 5 asymmetric induction in reactions between aldehydes and 4s 5 tert butyldimethylsilyloxy 4 hydroxypent 2 enyl tributyl stannane promoted by tin iv chloride
Journal of The Chemical Society-perkin Transactions 1, 1995Co-Authors: Robert J Maguire, Eric J ThomasAbstract:[(4S)-5-(Tert-Butyldimethylsilyloxy)-4-hydroxypent-2-enyl](tributyl)stannane 18 has been prepared from di-O-isopropylidene-D-mannitol 8. Oxidative cleavage of the mannitol derivative followed by condensation with triethyl phosphonoacetate and reduction gave the alcohol 10 which was converted into the xanthate 11. Deprotection gave the dihydroxy xanthate 12 which was protected as its bis-Tert-Butyldimethylsilyl ether 13. This rearranged on heating in toluene to give the dithiocarbonate 15 which reacted with tributyltin hydride under free radical conditions to give the [(4S)-4,5-bis(Tert-Butyldimethylsilyloxy)pent-2-enyl](tributyl)stannane 16 as an approximately 9:1 mixture of E- and Z-isomers. Deprotection and selective protection of the primary hydroxy Group provided the [(4S)-5-(Tert-Butyldimethylsilyloxy)-4-hydroxypent-2-enyl]stannane 18. As a shorter route, the primary hydroxy Group of the dihydroxy xanthate 12 was protected as its Tert-Butyldimethylsilyl ether 14 which underwent clean rearrangement into the dithiocarbonate 19 when heated in toluene. Reaction with tributyltin hydride under free radical conditions then gave the (5-Tert-Butyldimethylsilyloxy-4-hydroxypent-2-enyl)stannane 18. Treatment of this 4,5-disubstituted pentenylstannane with tin(IV) chloride generated an allyltin trichloride which reacted with aldehydes with excellent 1,5-asymmetric induction to give 1,5-syn-products, e.g. 20, 29–31 and 41. The stereoselectivity of these reactions would appear to be controlled by the 4-hydroxy substituent rather than by the 5-Tert-Butyldimethylsilyl Group. Aspects of the chemistry of these products, in particular their conversion into 2,6-disubstituted 5,6-dihydro-2H-pyrans, was investigated.
Takeshi Wada - One of the best experts on this subject based on the ideXlab platform.
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unprecedented mild acid catalyzed desilylation of the 2 o tert butyldimethylsilyl Group from chemically synthesized oligoribonucleotide intermediates via neighboring Group participation of the internucleotidic phosphate residue
Journal of the American Chemical Society, 1996Co-Authors: Shunichi Kawahara, Takeshi Wada, Mitsuo SekineAbstract:Hydrolytic removal of the 2‘-Tert-Butyldimethylsilyl (TBDMS) Group from a 2‘-O-TBDMS protected UpU dimer [U(2‘-Si)pU] (1) (Si = TBDMS) and related derivatives under various acidic conditions was studied in detail. First, desilylation of 1 by use of acetic acid was examined. Consequently, we made the unprecedented discovery that cleavage of the 2‘-silyl ether linkage occurred fastest at a very low concentration of acetic acid within the range of 5−10%, depending on the temperature. Formic acid could cleave the silyl ether much faster than acetic acid, but the relationship between the reaction rate and the concentration of acid was different from that of acetic acid. The use of 20−40% formic acid resulted in very effective elimination of the 2‘-TBDMS Group. Moreover, diluted HCl solution (pH 2.0) could cleave the Si−O bond faster than acetic acid at 30 °C. In contrast, the 2‘-silyl Group of the corresponding methylphosphonate derivative [U(2‘-Si)p(Me)U] (3) was much more stable than that of 1. In the case o...
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unprecedented mild acid catalyzed desilylation of the 2 o tert butyldimethylsilyl Group from chemically synthesized oligoribonucleotide intermediates via neighboring Group participation of the internucleotidic phosphate residue
Journal of the American Chemical Society, 1996Co-Authors: Shunichi Kawahara, Takeshi Wada, Mitsuo SekineAbstract:Hydrolytic removal of the 2‘-Tert-Butyldimethylsilyl (TBDMS) Group from a 2‘-O-TBDMS protected UpU dimer [U(2‘-Si)pU] (1) (Si = TBDMS) and related derivatives under various acidic conditions was st...
Robert J Maguire - One of the best experts on this subject based on the ideXlab platform.
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1 5 asymmetric induction in reactions between aldehydes and 4s 5 tert butyldimethylsilyloxy 4 hydroxypent 2 enyl tributyl stannane promoted by tin iv chloride
Journal of The Chemical Society-perkin Transactions 1, 1995Co-Authors: Robert J Maguire, Eric J ThomasAbstract:[(4S)-5-(Tert-Butyldimethylsilyloxy)-4-hydroxypent-2-enyl](tributyl)stannane 18 has been prepared from di-O-isopropylidene-D-mannitol 8. Oxidative cleavage of the mannitol derivative followed by condensation with triethyl phosphonoacetate and reduction gave the alcohol 10 which was converted into the xanthate 11. Deprotection gave the dihydroxy xanthate 12 which was protected as its bis-Tert-Butyldimethylsilyl ether 13. This rearranged on heating in toluene to give the dithiocarbonate 15 which reacted with tributyltin hydride under free radical conditions to give the [(4S)-4,5-bis(Tert-Butyldimethylsilyloxy)pent-2-enyl](tributyl)stannane 16 as an approximately 9:1 mixture of E- and Z-isomers. Deprotection and selective protection of the primary hydroxy Group provided the [(4S)-5-(Tert-Butyldimethylsilyloxy)-4-hydroxypent-2-enyl]stannane 18. As a shorter route, the primary hydroxy Group of the dihydroxy xanthate 12 was protected as its Tert-Butyldimethylsilyl ether 14 which underwent clean rearrangement into the dithiocarbonate 19 when heated in toluene. Reaction with tributyltin hydride under free radical conditions then gave the (5-Tert-Butyldimethylsilyloxy-4-hydroxypent-2-enyl)stannane 18. Treatment of this 4,5-disubstituted pentenylstannane with tin(IV) chloride generated an allyltin trichloride which reacted with aldehydes with excellent 1,5-asymmetric induction to give 1,5-syn-products, e.g. 20, 29–31 and 41. The stereoselectivity of these reactions would appear to be controlled by the 4-hydroxy substituent rather than by the 5-Tert-Butyldimethylsilyl Group. Aspects of the chemistry of these products, in particular their conversion into 2,6-disubstituted 5,6-dihydro-2H-pyrans, was investigated.
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1 5 asymmetric induction in reactions between aldehydes and 4s 5 tert butyldimethylsilyloxy 4 hydroxypent 2 enyl tributyl stannane promoted by tin iv chloride
Journal of The Chemical Society-perkin Transactions 1, 1995Co-Authors: Robert J Maguire, Eric J ThomasAbstract:[(4S)-5-(Tert-Butyldimethylsilyloxy)-4-hydroxypent-2-enyl](tributyl)stannane 18 has been prepared from di-O-isopropylidene-D-mannitol 8. Oxidative cleavage of the mannitol derivative followed by condensation with triethyl phosphonoacetate and reduction gave the alcohol 10 which was converted into the xanthate 11. Deprotection gave the dihydroxy xanthate 12 which was protected as its bis-Tert-Butyldimethylsilyl ether 13. This rearranged on heating in toluene to give the dithiocarbonate 15 which reacted with tributyltin hydride under free radical conditions to give the [(4S)-4,5-bis(Tert-Butyldimethylsilyloxy)pent-2-enyl](tributyl)stannane 16 as an approximately 9:1 mixture of E- and Z-isomers. Deprotection and selective protection of the primary hydroxy Group provided the [(4S)-5-(Tert-Butyldimethylsilyloxy)-4-hydroxypent-2-enyl]stannane 18. As a shorter route, the primary hydroxy Group of the dihydroxy xanthate 12 was protected as its Tert-Butyldimethylsilyl ether 14 which underwent clean rearrangement into the dithiocarbonate 19 when heated in toluene. Reaction with tributyltin hydride under free radical conditions then gave the (5-Tert-Butyldimethylsilyloxy-4-hydroxypent-2-enyl)stannane 18. Treatment of this 4,5-disubstituted pentenylstannane with tin(IV) chloride generated an allyltin trichloride which reacted with aldehydes with excellent 1,5-asymmetric induction to give 1,5-syn-products, e.g. 20, 29–31 and 41. The stereoselectivity of these reactions would appear to be controlled by the 4-hydroxy substituent rather than by the 5-Tert-Butyldimethylsilyl Group. Aspects of the chemistry of these products, in particular their conversion into 2,6-disubstituted 5,6-dihydro-2H-pyrans, was investigated.