Synthesis of crobarbatine acetate. A macrocyclic pyrrolizidine alkaloid ester

Huang, Jamin; Meinwald, Jerrold

doi:10.1021/ja00394a022

Cited by 48 publications

(7 citation statements)

References 5 publications

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“…Potassium carbonate deacylation promoted the 5-exo-trig closure to the key diol 17. 10 Periodate cleavage and oxidation of the resulting aldehyde 18 to the carboxylic acid 19 11 was followed by activation (with CDI) 12 and condensation of the acyl imidazole 20 with the dianion of ethyl 3-methyl-4-oxopentanoate. 13 Cyclization gave R-pyrone 21, 14 and methylation 15 The ratio of SNF4435 C and SNF4435 D from the biomimetic scheme is close to that found in nature (2.3:1).…”

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confidence: 99%

The Total Synthesis of (−)-SNF4435 C and (+)-SNF4435 D

Parker

Lim

2004

J. Am. Chem. Soc.

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The size and positioning of substituents on a tetraene, along with the Woodward-Hoffmann rules, control the relative stereochemistry at the four adjacent chiral centers that are generated in the 8pi/6pi electrocyclization cascade. A biomimetic synthesis of (-)-SNF4435 C and (+)-SNF4435 D exploits these steric effects and allows confirmation of the predicted absolute stereochemistry of the natural products.

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confidence: 99%

The Total Synthesis of (−)-SNF4435 C and (+)-SNF4435 D

Parker

Lim

2004

J. Am. Chem. Soc.

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“…The major component of this mixture was separated by preparative t.l.c. (31% yield) and was shown to be a mixture of the diastereoisomeric 9- (11) and 7-(12) senecioate monoesters of (+ )-retronecine by the following spectral data. A molecular ion at m/z 237 in the mass spectrum indicated the loss of carbon dioxide and water from the starting monoesters [( 9) and (10)].…”

Section: Resultsmentioning

confidence: 99%

Macrocyclic pyrrolizidine alkaloids. Synthesis and stereochemistry of (+)-dicrotaline (13β-hydroxy-13α-methyl-1,2-didehydrocrotalanine) and (+)-13-epi-dicrotaline

Brown¹,

Devlin²,

Robins³

1983

J. Chem. Soc., Perkin Trans. 1

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“…(+)- 8 : [ α ] 25 D +3.56 ( c 1.4, H 2 O). Lit 12b. (−)- 8 , [ α ] D −3.7 ( c 1.4, H 2 O) and [ α ] 18 D −8.0 ( c 0.2, H 2 O).…”

Section: Referencesmentioning

confidence: 99%

“…To extend this methodology further, the synthesis of trans -crobarbatic acid 8 is explored. trans -Crobarbatic acid 8 is the hydrolysis product of crobarbatine 6 and represents the cyclic form of necic acid 7 .…”

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Highly Diastereoselective Michael Addition of α-Hydroxy Acid Derivatives and Enantioselective Synthesis of (+)-Crobarbatic Acid

2001

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Michael addition of enolates of 2a and 2b to r,β-unsaturated esters took place selectively on different faces (Si and Re, respectively) of the double bond to give the corresponding products 4 and 5, respectively, with >98% de. Subsequent hydrolysis of these Micheal adducts gives 3,4-disubstituted γ-lactones with high enantiomeric excesses.The Michael addition reaction is one of the most important processes for C-C bond formation in organic synthesis. 1 A number of methods for asymmetric Michael addition were developed in the 1980s. 2 In previous reports, diastereoselective Michael addition reactions using R-amino acid derivatives as Michael donors have been examined as a method for introducing an R-substituent. 3 Stereoselective synthesis of an R-substituted R-hydroxy acid has been explored. 4 However, application of the Michael addition reaction with respect to the newly formed bond on the R-hydroxy acid derivative is quite rare 5 and has not been probed thoroughly. Recently, we have shown that chiral dioxolanones 2a and 2b, derived from 1, could be used for the preparation of enantiopure R-substituted R-hydroxy acids. 6 As a result, we decided to explore the diastereo-

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Synthesis of crobarbatine acetate. A macrocyclic pyrrolizidine alkaloid ester

Cited by 48 publications

References 5 publications

The Total Synthesis of (−)-SNF4435 C and (+)-SNF4435 D

The Total Synthesis of (−)-SNF4435 C and (+)-SNF4435 D

Macrocyclic pyrrolizidine alkaloids. Synthesis and stereochemistry of (+)-dicrotaline (13β-hydroxy-13α-methyl-1,2-didehydrocrotalanine) and (+)-13-epi-dicrotaline

Highly Diastereoselective Michael Addition of α-Hydroxy Acid Derivatives and Enantioselective Synthesis of (+)-Crobarbatic Acid

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