An enantiocontrolled cycloaddition approach to (+)-brefeldin A

Trost, Barry M.; Lynch, Joseph E.; Renaut, Patrice; Steinman, Douglas H.

doi:10.1021/ja00262a015

Cited by 108 publications

(25 citation statements)

References 2 publications

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“…Obviously, a double-bond isomerization of the enoate moiety, induced by conjugate addition of a nucleophile, and a ring closure had occurred. Analogous reactions have been observed by Trost et al [25] and Fürstner et al [26] Scheme 4. Formation of the γ-lactone 19 under Yamaguchi conditions.…”

Section: Resultssupporting

confidence: 77%

“…As pointed out previously, [25,26] nucleophilic reaction conditions must be avoided in order to prevent lactone formation. There are only a few corresponding methods, developed by Trost et al [30] and by Gais et al [31] We investigated the latter method, for which a push-pullsubstituted alkyne -4-(dimethylamino)but-3-yn-2-one -is used as reagent (Scheme 5), reacting with a carboxylic acid to give an enol ester of N,N-dimethyl-3-oxobutanamide.…”

Section: Resultsmentioning

confidence: 99%

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Syntheses and Biological Properties of Brefeldin Analogues

Förster¹,

Persch²,

Tverskoy³

et al. 2010

Eur J Org Chem

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Total and partial syntheses of brefeldin analogues are described. (6R)-Hydroxy-BFA (5) was obtained through a total synthesis from (1S,2R)-2-[(trityloxy)methyl]cyclopent-3-ene-1-carbonitrile (cis-8) in 13 steps. The BFA lactam analogue 6 was prepared via the key building block 25, which was accessed in four steps from BFA (1). (7S)-Amino-BFC (7) was obtained from 7-dehydro-BFA (3) by reductive amination.

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Section: Resultssupporting

confidence: 77%

Section: Resultsmentioning

confidence: 99%

Syntheses and Biological Properties of Brefeldin Analogues

Förster¹,

Persch²,

Tverskoy³

et al. 2010

Eur J Org Chem

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“…[32] These units are found in many natural products, including polyether antibiotics [33] and furanoterpenes. [34] For this reason, we have reported [35] an extremely simple and effective alternative procedure for the highly stereoselective synthesis of syn-or anti-α-alkyl-β-hydroxy sulfones by the reduction of the corresponding β-keto sulfones [36] with BH 3 ·py or lithium triethylborohydride (LiEt 3 BH) in the presence of TiCl 4 or dry CeCl 3 , respectively ( Table 2). The reduction of β-keto sulfones 6 with a THF solution of hydride in the presence of dry CeCl 3 proceeds with higher diastereoselectivity than the TiCl 4 Lewis acid promoted reaction (Table 2, entries 1 and 2).…”

Section: Diastereoselective Reduction Of α-Alkyl-β-keto Sulfonesmentioning

confidence: 99%

Diastereoselective Lewis Acid Mediated Reductions of α‐Alkyl‐β‐Functionalized Carbonyl Compounds

et al. 2005

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A high stereochemical induction has often been observed in the reduction of ketones with stereogenic centres close to the carbonyl function. The level of stereoselectivity is particularly high when “hard” donor groups such as nitrogen or oxygen atoms are present in the molecule. These results have been commonly explained in terms of a chelate‐controlled process. However, this interpretation has recently been challenged, and in many cases an open‐chain mechanism can better account for the observed results. Thus, Lewis‐acid‐mediated chelation and nonchelation control is one of the most fundamental and practical concepts in transferring a nucleophile moiety to carbonyl compounds. In order to clarify the role of a hard Lewis acid in controlling the stereochemical outcome of a given reaction, the Lewis acid mediated reduction of a series of α‐alkyl‐β‐functionalized carbonyl compounds with metallic hydrides in various solvents was recently investigated. In particular, the results derived from the reductions in the presence of dry CeCl3 were compared to those obtained under the same experimental conditions but in the presence of TiCl4, whose ability to form chelation complexes is well established. These investigations show a stereochemical outcome that is fully consistent with a chelation‐controlled pathway in the case of titanium, and an open‐chain‐controlled pathway in the case of CeCl3. The strongly chelating TiCl4 led to the syn isomer in high diastereomeric excess in noncoordinating solvents at –78 °C with borane–Lewis base complex reducing agents, while nonchelating CeCl3 produced a high excess of the anti isomer in coordinating solvents at the same temperature with metal borohydrides as reducing agent. Therefore, our method based on the choice of CeCl3 or TiCl4 as a Lewis acid under the reported conditions represents a significant contribution to the development of new stereoselective reductions of α‐alkyl‐β‐functionalized ketones. These procedures are one of the best known ways to obtain an alcoholic moiety. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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“…On going from the use of one equivalent of the sulfone carbanion to the use of two equivalents the yield of the β-keto sulfone 11 increased as expected, (49 to 74%, respectively). This is probably due to the fact that the generated β-keto sulfone is more acidic and can reprotonate the lithio(phenylsulfonyl)methane, [20,26] but no evidence for lactam opening by a carbanion of the resulting β-keto sulfone was found. Unlike in the reported additions to esters, [27] the use of methyl phenyl sulfone dilithium was shown to be less efficient in our case, producing a more complex mixture.…”

Section: Resultsmentioning

confidence: 98%

New Diastereoselective Route to 2‐Substituted cis‐(2S,5S)‐ and trans‐(2S,5R)‐5‐Alkylpyrrolidines as Indolizidine and Pyrrolizidine Scaffolds

Mota¹,

Chiaroni²,

Langlois³

2003

Eur J Org Chem

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A new and short stereoselective route to the synthesis of enantiopure cis-2,5-disubstituted pyrrolidines as indolizidine or pyrrolizidine scaffolds has been developed. The method, which uses (S)-pyroglutamic acid as a chiral starting material, is based on the ring opening of N-protected γ-lactams by alkyl phenyl sulfone carbanions, followed by desulfonylation and reductive amination of alkyl γ-amino ketones. The

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An enantiocontrolled cycloaddition approach to (+)-brefeldin A

Cited by 108 publications

References 2 publications

Syntheses and Biological Properties of Brefeldin Analogues

Syntheses and Biological Properties of Brefeldin Analogues

Diastereoselective Lewis Acid Mediated Reductions of α‐Alkyl‐β‐Functionalized Carbonyl Compounds

New Diastereoselective Route to 2‐Substituted cis‐(2S,5S)‐ and trans‐(2S,5R)‐5‐Alkylpyrrolidines as Indolizidine and Pyrrolizidine Scaffolds

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