Chiral Resolution and Absolute Configuration of 3α,6β-Dicinnamoyloxytropane and 3α,6β-Di(1-ethyl-1H-pyrrol-2-ylcarbonyloxy)tropane, Constituents of Erythroxylum Species

Muñoz, Marcelo A.; Arriagada, Solange; Joseph‐Nathan, Pedro

doi:10.1177/1934578x1400900109

Cited by 4 publications

(4 citation statements)

References 17 publications

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“…From this procedure an enantiopure sample of the second eluted peak, OR (+)‐6‐benzoyl‐3‐tropanol, was obtained and subjected to VCD measurements in the 1550–950 cm ‐1 region. The VCD technique has shown to be particularly useful for the analysis of 3α,6β‐tropanediol derivatives such as 1 , for which we have described a signal pattern which is characteristic of the AC of a tropane, but is independent of the substituents identity . In this case, the VCD spectrum showed the same phases of the signals observed in other 3α,6β‐tropanediol derivatives having the (1 S ,3 R ,5 S ,6 R ) AC (Fig.…”

Section: Resultssupporting

confidence: 55%

“…The VCD bands of 1 arise only from the tropane skeleton since the substituents lack of stereogenic centers. Therefore, it could be assumed that comparison of the VCD spectra is tropane 3,6‐diesters with that of monoester 1 , would suffice to determine the AC of the later. In addition, naturally occurring mixtures of 3,6‐diesters, of mixtures of 6‐acyloxytropane‐3‐ols, and a mixture of 6‐acyloxytropane‐3‐ol with 3‐acyloxytropane‐6‐ol have been assigned successfully using this empirical methodology .…”

Section: Resultsmentioning

confidence: 99%

“…Other related compounds include 3α,6β‐dibenzoyloxytropane ( 2 ), found in E. cuneatum and E. caatingae , and 3α,6β‐di(1‐methyl‐1H‐pyrrol‐2‐ylcarbonyloxy)tropane ( 3 ) (Fig. ) found in E. vacciniifolium , both recently studied using vibrational circular dichroism (VCD) .…”

Section: Introductionmentioning

confidence: 99%

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Enantiomeric high-performance liquid chromatography resolution and absolute configuration of 6β-benzoyloxy-3α-tropanol

2016

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The absolute configuration of the naturally occurring isomers of 6β-benzoyloxy-3α-tropanol (1) has been established by the combined use of chiral high-performance liquid chromatography with electronic circular dichroism detection and optical rotation detection. For this purpose (±)-1, prepared in two steps from racemic 6-hydroxytropinone (4), was subjected to chiral high-performance liquid chromatography with electronic circular dichroism and optical rotation detection allowing the online measurement of both chiroptical properties for each enantiomer, which in turn were compared with the corresponding values obtained from density functional theory calculations. In an independent approach, preparative high-performance liquid chromatography separation using an automatic fraction collector, yielded an enantiopure sample of OR (+)-1 whose vibrational circular dichroism spectrum allowed its absolute configuration assignment when the bands in the 1100-950 cm(-1) region were compared with those of the enantiomers of esters derived from 3α,6β-tropanediol. In addition, an enantiomerically enriched sample of 4, instead of OR (±)-4, was used for the same transformation sequence, whose high-performance liquid chromatography follow-up allowed their spectroscopic correlation. All evidences lead to the OR (+)-(1S,3R,5S,6R) and OR (-)-(1R,3S,5R,6S) absolute configurations, from where it follows that samples of 1 isolated from Knightia strobilina and Erythroxylum zambesiacum have the OR (+)-(1S,3R,5S,6R) absolute configuration, while the sample obtained from E. rotundifolium has the OR (-)-(1R,3S,5R,6S) absolute configuration.

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Section: Resultssupporting

confidence: 55%

Section: Resultsmentioning

confidence: 99%

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Enantiomeric high-performance liquid chromatography resolution and absolute configuration of 6β-benzoyloxy-3α-tropanol

2016

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“…Moreover, the optical activity of 2 is conserved in these derivatives, and therefore, optical isomerism is added as a further layer of complexity in their structural elucidation. [3][4][5] The absolute configuration of natural and synthetic tropanediol esters has been achieved previously using different strategies that include total synthesis, 6 1 H-NMR spectroscopy, 7,8 electronic, 9,10 and vibrational circular dichroism, [10][11][12][13][14][15] and optical rotation calculations. 10 Nevertheless, many mono and diesters of tropanediol remain without an established absolute configuration, and the stereochemical preferences of the diverse species that produce them is, in many cases, unknown.…”

Section: Introductionmentioning

confidence: 99%

Absolute Configuration of Isomeric Mono-Acetyl Tropane Alkaloids Using Chromatography-Assisted Chemical Correlation

Muñoz,

Cabrera Z.

2023

Natural Product Communications

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Objective: To establish the absolute configurations of isomeric 6β-acetyl-3α-tropanol (3) and 3α-acetyl-6β-tropanol (4), constituents of several species of Datura and other genera, using a combination of a simple hemi-synthetic pathway starting from racemic 6β-hydroxytropinone (1) to produce 3α,6β-tropanediol (2), and the use of chiral liquid chromatography coupled with mass and laser optical rotation detectors (LC-MS and LC-OR). Methods: In the case of 3, mono acetylation of the more reactive OH group at C-6 in 2 was achieved under controlled reaction conditions, while more vigorous conditions produced exclusively 3α,6β-diacetyltropane (5). On the other hand, isomer 4 was obtained by partial hydrolysis of the acetyl group at C-6 in 5. Samples of the three compounds were then subjected to chiral LC-MS and LC-OR, which showed chromatograms composed of two peaks of opposite optical rotation. Next, ten consecutive LC injections followed by fraction collection of the column elution, produced a set of micro-scale samples of opposite enantiomeric composition for each mono ester, which were then derivatized by further acetylation to convert the partially enantioenriched samples into their corresponding diacetates. The resulting samples were then evaluated using LC-MS, which allowed the correlation between the enantiomers of 3 and 4 with those of 5. Results: Considering that the absolute configuration of (−)-5 has been assigned previously as (1 S, 3 S, 5 R, 6 S), these chromatographic comparisons established the absolute configurations of monoacetates 3 and 4 as (−)-(1 S, 3 S, 5 R, 6 S)-3 and (+)-(1 R, 3 R, 5 S, 6 R)-3, and (−)-(1 S, 3 S, 5 R, 6 S)-4 and (+)-(1 R, 3 R, 5 S, 6 R)-4, respectively. Conclusion: A methodology based on chiral liquid chromatography allowed the establishment of the absolute configuration of isomeric monoacetates of tropandiol 3 and 4, directly from the racemic mixtures, and without resorting to the isolation of enantiomerically pure samples.

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Vibrational Circular Dichroism: Recent Advances for the Assignment of the Absolute Configuration of Natural Products

Burgueño‐Tapia

Joseph‐Nathan

2015

Natural Product Communications

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Vibrational circular dichroism (VCD) emerged during the last decade as a reliable tool for the absolute configuration (AC) determination of organic compounds. The principles, instrumentation, and methodology applied prior to early 2013 were recently reviewed by us. Since VCD is a very dynamic field, the aim of this review is to update VCD advances for the AC assignment of terpenoids, aromatic compounds, alkaloids, and other natural products for the 2013-2014 period, when VCD was applied to the AC assignment of some 70 natural products. In addition, although discovered in 2012, a brief introduction to the VCD exciton coupling approach and its applications in natural products AC assignment is presented.

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Chiral Resolution and Absolute Configuration of 3α,6β-Dicinnamoyloxytropane and 3α,6β-Di(1-ethyl-1H-pyrrol-2-ylcarbonyloxy)tropane, Constituents of Erythroxylum Species

Cited by 4 publications

References 17 publications

Enantiomeric high-performance liquid chromatography resolution and absolute configuration of 6β-benzoyloxy-3α-tropanol

Enantiomeric high-performance liquid chromatography resolution and absolute configuration of 6β-benzoyloxy-3α-tropanol

Absolute Configuration of Isomeric Mono-Acetyl Tropane Alkaloids Using Chromatography-Assisted Chemical Correlation

Vibrational Circular Dichroism: Recent Advances for the Assignment of the Absolute Configuration of Natural Products

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