Asymmetric Induction in Aza-Claisen Rearrangement of Carboxamide Enolates. Effect of Chiral Auxiliary on Nitrogen.

Tsunoda, Tetsuto; Sakai, Makiko; Sasaki, O.; Sako, Y.; Hondo, Yuka; Itô, Shô

doi:10.1016/s0040-4039(00)91698-8

Cited by 38 publications

(21 citation statements)

References 9 publications

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“…Coupling of the carboxylic acid, formed from the hydrolysis of racemic amide 14,t ot he chiral amine (S)-(À)-a-methyl-benzylamine gave an inseparable mixture of diastereomers,t hus confirming that had the chiral aza-Claisen been successful, the diastereomers formed would not have been separable,which is in contrast to previous aza-Claisen-derived amides. [4,14] Therefore,anew strategy was designed using an Evans chiral auxiliary,f or which as tereoselective allylation would enable induction of the desired stereocenters (Scheme 3).…”

Section: Angewandte Chemiementioning

confidence: 99%

“…Following the successful racemic synthesis of 1 and 2,a n enantioselective synthesis was then attempted to determine the absolute stereochemistry of these natural products.Initial attempts at an enantioselective aza-Claisen rearrange-ment [4,14] were unsuccessful (see Scheme S6). Coupling of the carboxylic acid, formed from the hydrolysis of racemic amide 14,t ot he chiral amine (S)-(À)-a-methyl-benzylamine gave an inseparable mixture of diastereomers,t hus confirming that had the chiral aza-Claisen been successful, the diastereomers formed would not have been separable,which is in contrast to previous aza-Claisen-derived amides.…”

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confidence: 99%

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Total Synthesis of Ovafolinins A and B: Unique Polycyclic Benzoxepin Lignans through a Cascade Cyclization

Davidson

Barker

2017

Angew Chem Int Ed

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Ovafolinins A and B, isolated from Lyonia ovalifolia var. elliptica, are lignans that contain a unique bridged structure containing a penta- and tetracyclic benzoxepin and an aryl tetralin. We report the first total synthesis of these natural products in which an acyl-Claisen rearrangement was initially utilized to construct the lignan backbone with correct relative stereochemistry. Judicious use of a bulky protecting group placed reactive moieties in the correct orientation, thereby resulting in a cascade reaction to form the bridged benzoxepin/aryl tetralin from a linear precursor in a single step. Modification of this route allowed the enantioselective synthesis of (+)-ovafolinins A and B, which confirmed the absolute stereochemistry, and comparison of optical rotation suggests that these compounds are found as scalemic mixtures in nature.

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Section: Angewandte Chemiementioning

confidence: 99%

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confidence: 99%

Total Synthesis of Ovafolinins A and B: Unique Polycyclic Benzoxepin Lignans through a Cascade Cyclization

Davidson

Barker

2017

Angew Chem Int Ed

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“…Advances in the ACR, such as the charge‐accelerated ACR, offer ring expansions with defined stereochemistry, and several pioneering examples have been reported, including by ourselves. We reported a ring‐expansion reaction of 1‐acyl‐2‐vinylpiperidines and 1‐acyl‐2‐vinylpiperazines (Scheme A), based on studies of the amide‐enolate‐induced ACR . In addition, the first synthesis of fluvirucinine A 1 ( 8 ) was accomplished as an application of this reaction (Scheme B) .…”

Section: Acr‐induced Ring‐expansion Strategies For the Synthesis Of Mmentioning

confidence: 99%

Advances in Aza‐Claisen‐Rearrangement‐Induced Ring‐Expansion Strategies

2017

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The aza-Claisen rearrangement,a lso known as the 3-aza-Coper earrangement, has attracted significant attention because it can be used as ac omplimentarym ethodt o access ad iverse range of useful organic molecules. The presence of an itrogen atom at the 3-position enables the tethering of various-sized azacycles, thereby giving ring-expansion strategiest hat take advantage of the aza-Claisen rearrangementadistinct advantage comparedt oo ther [3,3]-sigmatropic rearrangements. Recent advances in aza-Claisen rearrangements have facilitatedo therwise-inaccessible ring expansions in ah ighly stereoselective manner. The utility of aza-Claisen-rearrangement-induced ring-expansion strategies has been exemplified in the synthesis of ad iverse range of naturalp roducts. This Focus Review summarizes recent advancesi na za-Claisen-rearrangement-induced ring-expansion strategy, in particular applicationsi nt he synthesis of bioactive alkaloids.

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“…Following the successful racemic synthesis of 1 and 2 , an enantioselective synthesis was then attempted to determine the absolute stereochemistry of these natural products. Initial attempts at an enantioselective aza‐Claisen rearrangement were unsuccessful (see Scheme S6). Coupling of the carboxylic acid, formed from the hydrolysis of racemic amide 14 , to the chiral amine ( S )‐(−)‐α‐methyl‐benzylamine gave an inseparable mixture of diastereomers, thus confirming that had the chiral aza‐Claisen been successful, the diastereomers formed would not have been separable, which is in contrast to previous aza‐Claisen‐derived amides .…”

Section: Figurementioning

confidence: 99%

Total Synthesis of Ovafolinins A and B: Unique Polycyclic Benzoxepin Lignans through a Cascade Cyclization

Davidson¹,

Barker

2017

Angewandte Chemie

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Ovafolinins A and B, isolated from Lyonia ovalifolia var. elliptica, are lignans that contain a unique bridged structure containing a penta‐ and tetracyclic benzoxepin and an aryl tetralin. We report the first total synthesis of these natural products in which an acyl‐Claisen rearrangement was initially utilized to construct the lignan backbone with correct relative stereochemistry. Judicious use of a bulky protecting group placed reactive moieties in the correct orientation, thereby resulting in a cascade reaction to form the bridged benzoxepin/aryl tetralin from a linear precursor in a single step. Modification of this route allowed the enantioselective synthesis of (+)‐ovafolinins A and B, which confirmed the absolute stereochemistry, and comparison of optical rotation suggests that these compounds are found as scalemic mixtures in nature.

show abstract

Asymmetric Induction in Aza-Claisen Rearrangement of Carboxamide Enolates. Effect of Chiral Auxiliary on Nitrogen.

Cited by 38 publications

References 9 publications

Total Synthesis of Ovafolinins A and B: Unique Polycyclic Benzoxepin Lignans through a Cascade Cyclization

Total Synthesis of Ovafolinins A and B: Unique Polycyclic Benzoxepin Lignans through a Cascade Cyclization

Advances in Aza‐Claisen‐Rearrangement‐Induced Ring‐Expansion Strategies

Total Synthesis of Ovafolinins A and B: Unique Polycyclic Benzoxepin Lignans through a Cascade Cyclization

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