Total synthesis of a cuticular hydrocarbon from the cane beetle Antitrogus parvulus: confirmation of the relative stereochemistry

Basar, Norazah; Líu, Hao; Negi, Devendra Singh; Sirat, Hasnah Mohd; Morris, Gareth A.; Thomas, Eric J.

doi:10.1039/c2ob06906g

Cited by 13 publications

(21 citation statements)

References 19 publications

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“…Reductive removal of the phenylsulfonyl group gave the 4,6,8,10,16-pentamethyldocosanes 2 and 4 . 3 These final samples have 1 H NMR spectra at 700 MHz that are indistinguishable, but the subsequent 13 C NMR analysis showed that their isomeric purity is at least 95%.…”

Section: Resultsmentioning

confidence: 98%

“…3 The synthesis is summarized here with additional details. Complete experimental information and compound characterization data are found in the Supporting Information.…”

Section: Resultsmentioning

confidence: 99%

“…We show this by comparing the newly recorded sets of spectra of 2 and 4 to the original published spectra. 3 As is common, these original spectra were recorded at ambient temperature, without variable temperature control.…”

Section: Resultsmentioning

confidence: 99%

“…Not surprisingly, these data lists are very similar. 3 Indeed, so similar that we had to consider the possibility that the spectra of synthetic 2 and 4 were substantially identical and that any tiny observed differences were due to error. If that were true, then the structure of the natural product could not be assigned.…”

Section: Introductionmentioning

confidence: 99%

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Systematic Comparison of Sets of ¹³C NMR Spectra That Are Potentially Identical. Confirmation of the Configuration of a Cuticular Hydrocarbon from the Cane Beetle Antitrogus parvulus

et al. 2014

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A systematic process is introduced to compare 13C NMR spectra of two (or more) candidate samples of known structure to a natural product sample of unknown structure. The process is designed for the case where the spectra involved can reasonably be expected to be very similar, perhaps even identical. It is first validated by using published 13C NMR data sets for the natural product 4,6,8,10,16,18-hexamethyldocosane. Then the stereoselective total syntheses of two candidate isomers of the related 4,6,8,10,16-pentamethyldocosane natural product are described, and the process is applied to confidently assign the configuration of the natural product as (4S,6R,8R,10S,16S). This is accomplished even though the chemical shift differences between this isomer and its (16R)-epimer are only ±5–10 ppb (±0.005–0.01 ppm).

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Section: Resultsmentioning

confidence: 98%

“…3 The synthesis is summarized here with additional details. Complete experimental information and compound characterization data are found in the Supporting Information.…”

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Systematic Comparison of Sets of ¹³C NMR Spectra That Are Potentially Identical. Confirmation of the Configuration of a Cuticular Hydrocarbon from the Cane Beetle Antitrogus parvulus

et al. 2014

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“…Inspired by their elegant pioneer work, we studied the alkylation of 11 with different alkyl iodides under our conditions. We were pleased to find that the cross-coupling reaction was carried out smoothly affording 2-alkyl-4-iodooxazole as the only coupling product in good yields (entries [11][12][13][14]. Confirmation of this selectivity was exemplified by lithiation of 4-iodooxazole 9j with nBuLi, and quenching with H 2 O to obtain the known compound 2-butyloxazole.…”

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An efficient preparation of 2-alkyl-oxazoles from 2-iodooxazoles

Zhang

Lee

Liu

et al. 2013

Tetrahedron Letters

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a b s t r a c tAn efficient synthesis toward 2-alkyl substituted oxazoles has been achieved through Suzuki cross-coupling reaction. Treatment of various alkyl iodides with 9-MeO-BBN, followed by in situ palladium-catalyzed carbon-carbon formation with 2-iodooxazoles obtained the 2-alkyl substituted oxazoles in good to excellent yields. Regioselective C2-alkylation on 2,4-di-iodooxazole under the same reaction conditions was firstly disclosed.Ó 2013 Elsevier Ltd. All rights reserved.Oxazoles are widely distributed in natural products, and many of them possess significant biological activities including antifungal, cytotoxic, and anthelmintic properties.1 Oxazoles have also been utilized as important building blocks in organic syntheses and drug developments. 2,3 The potent biological activity and the prevalence of oxazoles in natural products and drug candidates have stimulated intensive interests in the synthesis of these heterocycles.2b,2d-gAs an important structural motif, 2-alkyl substituted oxazole ring has been found in many oxazole-containing natural products, including the phenoxan, 1g noricumazoles, 4 hennoxazoles, 1f and leiodolides A & B.1d Conventional synthesis of 2-alkyl oxazoles was conducted in multistep reaction, 2f,5 and to the best of our knowledge, direct alkylation at the C2 position is challenging and has very limited success to date. 6 Due to the structural significance in drug development, it has a strong demanding to explore new synthetic methodologies to access this highly functionalized heterocycles in a straightforward and efficient way. Herein, we wish to report our result for the synthesis of 2-alkyl-oxazole via Suzuki-Miyaura cross-coupling reaction between 2-iodooxazoles and alkylboronates.In our efforts toward the total synthesis of leiodolides (Fig. 1), showing potential cytotoxicity against HCT-116 human colon carcinoma cells, 1d we have recently reported the stereoselective synthesis of the C22-C31 fragment of leiodolide A employing a diastereoselective Seebach alkylation and a Brown's P2-Ni catalyzed cis-alkyne semihydrogenation in the presence of a vinyl iodide. 7 To build fragments C1-C17 of leiodolide A, we eagerly required a method for the facile assembly of this densely functionalized 2-alkyl-substitution oxazole derivative, exemption from multistep construction of the oxazole ring. The exploration started from a direct alkylation on oxazole C-2 position through C-2 lithiation and a subsequent quenching with an electrophile, using ethyl oxazole-4-carboxylate (3) and iodomethane (4) as the testing system. Treatment of 3 with lithium base (LiHMDS or t-BuLi) in anhydrous THF, with or without 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU), resulted in the recovery of major starting materials. In order to exclude the electron-withdrawing effect of carboxylate at C4-position, TBS group protected substrate 4-(tert-butyl-dimethylsilyloxy)methyloxazole (5) was applied, unfortunately, no desired product was observed. Attempted C-2 alkylation on oxazole through lithium-h...

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(Bicyclo[2.2.1]hepta-2,5-diene)[1,4-bis(diphenylphosphino)butane]rhodium(I) Tetrafluoroborate

Evans

Miller

Brown

et al.

Encyclopedia of Reagents for Organic Synthesis

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Total synthesis of a cuticular hydrocarbon from the cane beetle Antitrogus parvulus: confirmation of the relative stereochemistry

Cited by 13 publications

References 19 publications

Systematic Comparison of Sets of ¹³C NMR Spectra That Are Potentially Identical. Confirmation of the Configuration of a Cuticular Hydrocarbon from the Cane Beetle Antitrogus parvulus

Systematic Comparison of Sets of ¹³C NMR Spectra That Are Potentially Identical. Confirmation of the Configuration of a Cuticular Hydrocarbon from the Cane Beetle Antitrogus parvulus

An efficient preparation of 2-alkyl-oxazoles from 2-iodooxazoles

(Bicyclo[2.2.1]hepta-2,5-diene)[1,4-bis(diphenylphosphino)butane]rhodium(I) Tetrafluoroborate

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Total synthesis of a cuticular hydrocarbon from the cane beetle Antitrogus parvulus: confirmation of the relative stereochemistry

Cited by 13 publications

References 19 publications

Systematic Comparison of Sets of 13C NMR Spectra That Are Potentially Identical. Confirmation of the Configuration of a Cuticular Hydrocarbon from the Cane Beetle Antitrogus parvulus

Systematic Comparison of Sets of 13C NMR Spectra That Are Potentially Identical. Confirmation of the Configuration of a Cuticular Hydrocarbon from the Cane Beetle Antitrogus parvulus

An efficient preparation of 2-alkyl-oxazoles from 2-iodooxazoles

(Bicyclo[2.2.1]hepta-2,5-diene)[1,4-bis(diphenylphosphino)butane]rhodium(I) Tetrafluoroborate

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Systematic Comparison of Sets of ¹³C NMR Spectra That Are Potentially Identical. Confirmation of the Configuration of a Cuticular Hydrocarbon from the Cane Beetle Antitrogus parvulus

Systematic Comparison of Sets of ¹³C NMR Spectra That Are Potentially Identical. Confirmation of the Configuration of a Cuticular Hydrocarbon from the Cane Beetle Antitrogus parvulus