The total synthesis of the polyether antibiotic X-206

Evans, David A.; Bender, Steven L.; Morris, Joel

doi:10.1021/ja00216a026

Cited by 264 publications

(142 citation statements)

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“…The high enantioselectivity of the double AD reaction in Scheme 3 was proven by an alternative preparation of bis-Weinreb amide 12 via an Evans aldol reaction [18] of the enantiomerically pure glycolic acid derivative 17 [19] with dialdehyde 18, [20] which succeeded efficiently in a two-directional fashion (Scheme 4). The resultant C 2 -symmetrical product 19 was transformed to 12 by cleavage of the auxiliaries [19] to give 20 followed by debenzylation and acetalization {12 from 9: A sequence consisting of dihydroxylation, global reduction of all carbonyl groups and chemoselective blocking of the two primary alcohols converted 16 to the bis-tert-butyldiphenylsilyl ether 21, Dess-Martin oxidation [21] of which yielded the pseudo C 2 -symmetrical diketone 22 (Scheme 5).…”

Section: Scheme 2 Model Studiesmentioning

confidence: 99%

“…The resultant C 2 -symmetrical product 19 was transformed to 12 by cleavage of the auxiliaries [19] to give 20 followed by debenzylation and acetalization {12 from 9: A sequence consisting of dihydroxylation, global reduction of all carbonyl groups and chemoselective blocking of the two primary alcohols converted 16 to the bis-tert-butyldiphenylsilyl ether 21, Dess-Martin oxidation [21] of which yielded the pseudo C 2 -symmetrical diketone 22 (Scheme 5). In the following key step, 22 was indeed selectively cyclized to give the desired heterobicyclic acetal, whereby a partial desilylation occurred.…”

Section: Scheme 2 Model Studiesmentioning

confidence: 99%

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A Symmetry‐Based Synthesis of the Heterobicyclic Core of the Zaragozic Acids/Squalestatins

2009

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The pseudo C 2 -symmetrical diketone 22 was efficiently constructed from furan-3,4-dimethanol (7) using a two-directional route featuring a double asymmetric dihydroxylation. Acidic hydrolysis of the cyclopentylidene acetals of 22 triggered a selective cyclization of the resulting hexaol diketone to generate the 2,8-dioxabicycloA C H T U N G T R E N N U N G [3.2.1]octane core of the zaragozic acids/squalestatins. Chemoselective oxidative cleavage of a superfluous twocarbon appendage and further functional group manipulations yielded the enantiomerically pure tri-A C H T U N G T R E N N U N G ester 30, which offers itself as a general heterobicyclic building block for naturally occurring zaragozic acids/squalestatins and unnatural analogues.

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Section: Scheme 2 Model Studiesmentioning

confidence: 99%

Section: Scheme 2 Model Studiesmentioning

confidence: 99%

A Symmetry‐Based Synthesis of the Heterobicyclic Core of the Zaragozic Acids/Squalestatins

2009

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“…Only the six-membered ring ether was formed. After extensive experimentation we found that demercuration was most cleanly achieved by reduction with nBu 3 SnH [19] to furnish 18, which already features the complete skeleton of gelsedine.…”

Section: Total Synthesis Of ()-Gelsedinementioning

confidence: 99%

Total Synthesis of (+)-Gelsedine

Henegouwen

Fieseler

Rutjes

et al. 1999

Angew. Chem. Int. Ed.

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A novel iodide-promoted, allene-terminated cyclization of an N-acyliminium ion, a stereoselective Heck spirocyclization, and a chemoselective demethylation at the nitrogen atom of an oxindole are the key transformations in the first total synthesis of the indole alkaloid (+)-gelsedine (1). This dextrorotatory form of natural gelsedine was formed as a single enantiomer in 21 steps from (S)-malic acid.

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“…A solution of maduramicin free acid (200 mg) in ether was allowed to react with ethereal diazomethane until nitrogen evolution ceased and the yellow color persisted (Evans et al, 1988). After additional 30 min, the solution was concentrated and the residue was purified by preparative thin layer chromatography.…”

Section: Synthesis O F Maduramicin Methyl Ester Derivative (La)mentioning

confidence: 99%

Phytotoxic and Photosynthetic Activities of Maduramicin and Maduramicin Methyl Ester

Gutiérrez-Lugo

Lotina‐Hennsen

Farrés

et al. 1999

Zeitschrift Für Naturforschung C

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The polyether antibiotic maduramicin and its methyl ester derivative inhibited photophos phorylation and proton uptake in isolated spinach chloroplasts. Both compounds also en hanced basal and phosphorylating electron transport and stimulated Mg2+-dependent A T Pase activity, therefore, they behave as uncouplers of photophosphorylation being the methyl ester derivative more potent than the parent compound. On the other hand, maduramicin inhibited germination and radicle elongation of several crop and weed species. In addition, the antibiotic caused phytotoxic injury and fresh weight reduction to 4-to-6 week old seed lings of two weed and two crop species when applied at 1 0~4 m by foliar application in the greenhouse.

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The total synthesis of the polyether antibiotic X-206

Cited by 264 publications

References 0 publications

A Symmetry‐Based Synthesis of the Heterobicyclic Core of the Zaragozic Acids/Squalestatins

A Symmetry‐Based Synthesis of the Heterobicyclic Core of the Zaragozic Acids/Squalestatins

Total Synthesis of (+)-Gelsedine

Phytotoxic and Photosynthetic Activities of Maduramicin and Maduramicin Methyl Ester

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