Abstract
A methodology to determine the enantiomeric excess and the absolute configuration (AC) of natural epoxythymols was developed and tested using five constituents of Ageratina glabrata. The methodology is based on enantiomeric purity determination employing 1,1'-bi-2-naphthol (BINOL) as a chiral solvating agent combined with vibrational circular dichroism (VCD) measurements and calculations. The conformational searching included an extensive Monte Carlo protocol that considered the rotational barriers to cover the whole conformational spaces. (+)-(8S)-10-Benzoyloxy-6-hydroxy-8,9-epoxythymol isobutyrate (1), (+)-(8S)-10-acetoxy-6-methoxy-8,9-epoxythymol isobutyrate (4), and (+)-(8S)-10-benzoyloxy-6-methoxy-8,9-epoxythymol isobutyrate (5) were isolated as enantiomerically pure constituents, while 10-isobutyryloxy-8,9-epoxythymol isobutyrate (2) was obtained as a 75:25 (8S)/(8R) scalemic mixture. In the case of 10-benzoyloxy-8,9-epoxythymol isobutyrate (3), the BINOL methodology revealed a 56:44 scalemic mixture and the VCD measurement was beyond the limit of sensitivity since the enantiomeric excess is only 12%. The racemization process of epoxythymol derivatives was studied using compound 1 and allowed the clarification of some stereochemical aspects of epoxythymol derivatives since their ACs have been scarcely analyzed and a particular behavior in their specific rotations was detected. In more than 30 oxygenated thymol derivatives, including some epoxythymols, the reported specific rotation values fluctuate from -1.6 to +1.4 passing through zero, suggesting the presence of scalemic and close to racemic mixtures, since enantiomerically pure natural constituents showed positive or negative specific rotations greater than 10 units.
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Claims 8
Claim · model-written summary
Three epoxythymol constituents were isolated as enantiomerically pure constituents.
- Taxon
- Ageratina glabrata
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Ageratina glabratae1 - Outcome
- were isolated as enantiomerically pure constituentse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
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Verbatim
e1“A methodology to determine the enantiomeric excess and the absolute configuration (AC) of natural epoxythymols was developed and tested using five constituents of Ageratina glabrata”
e2“(+)-(8S)-10-Benzoyloxy-6-hydroxy-8,9-epoxythymol isobutyrate (1), (+)-(8S)-10-acetoxy-6-methoxy-8,9-epoxythymol isobutyrate (4), and (+)-(8S)-10-benzoyloxy-6-methoxy-8,9-epoxythymol isobutyrate (5) were isolated as enantiomerically pure constituents”
Claim · model-written summary
Compound 2 was obtained as a 75:25 (8S)/(8R) scalemic mixture.
- Taxon
- Ageratina glabrataAgeratina glabratae1
- Outcome
- scalemic mixturee2
- Value
- 75:25e2
- Qualifier
- 10-isobutyryloxy-8,9-epoxythymol isobutyrate (2)e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“A methodology to determine the enantiomeric excess and the absolute configuration (AC) of natural epoxythymols was developed and tested using five constituents of Ageratina glabrata”
e2“10-isobutyryloxy-8,9-epoxythymol isobutyrate (2) was obtained as a 75:25 (8S)/(8R) scalemic mixture”
Claim · model-written summary
Compound 3 was a 56:44 scalemic mixture by the BINOL methodology.
- Taxon
- Ageratina glabrataAgeratina glabratae1
- Outcome
- scalemic mixturee2
- Value
- 56:44e2
- Qualifier
- 10-benzoyloxy-8,9-epoxythymol isobutyrate (3)e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“A methodology to determine the enantiomeric excess and the absolute configuration (AC) of natural epoxythymols was developed and tested using five constituents of Ageratina glabrata”
e2“In the case of 10-benzoyloxy-8,9-epoxythymol isobutyrate (3), the BINOL methodology revealed a 56:44 scalemic mixture and the VCD measurement was beyond the limit of sensitivity since the enantiomeric excess is only 12%”
Claim · model-written summary
Compound 3 had an enantiomeric excess of only 12%, beyond the VCD sensitivity limit.
- Taxon
- Ageratina glabrataAgeratina glabratae1
- Outcome
- enantiomeric excesse2
- Value
- 12%e2
- Qualifier
- the VCD measurement was beyond the limit of sensitivitye2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“A methodology to determine the enantiomeric excess and the absolute configuration (AC) of natural epoxythymols was developed and tested using five constituents of Ageratina glabrata”
e2“In the case of 10-benzoyloxy-8,9-epoxythymol isobutyrate (3), the BINOL methodology revealed a 56:44 scalemic mixture and the VCD measurement was beyond the limit of sensitivity since the enantiomeric excess is only 12%”
Claim · model-written summary
Racemization of compound 1 clarified some stereochemical aspects of epoxythymol derivatives.
- Taxon
- Ageratina glabrataAgeratina glabratae1
- Outcome
- clarification of some stereochemical aspects of epoxythymol derivativese2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“A methodology to determine the enantiomeric excess and the absolute configuration (AC) of natural epoxythymols was developed and tested using five constituents of Ageratina glabrata”
e2“The racemization process of epoxythymol derivatives was studied using compound 1 and allowed the clarification of some stereochemical aspects of epoxythymol derivatives”
Claim · model-written summary
Epoxythymol derivatives showed a particular behavior in their specific rotations.
- Taxon
- Ageratina glabrataAgeratina glabratae1
- Outcome
- specific rotationse2
- Qualifier
- a particular behaviore2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“A methodology to determine the enantiomeric excess and the absolute configuration (AC) of natural epoxythymols was developed and tested using five constituents of Ageratina glabrata”
e2“since their ACs have been scarcely analyzed and a particular behavior in their specific rotations was detected”
Claim · model-written summary
Reported specific rotations of more than 30 oxygenated thymol derivatives fluctuate from -1.6 to +1.4 through zero.
- Taxon
- Ageratina glabrataAgeratina glabratae1
- Outcome
- reported specific rotation valuese2
- Value
- from -1.6 to +1.4e2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“A methodology to determine the enantiomeric excess and the absolute configuration (AC) of natural epoxythymols was developed and tested using five constituents of Ageratina glabrata”
e2“In more than 30 oxygenated thymol derivatives, including some epoxythymols, the reported specific rotation values fluctuate from -1.6 to +1.4 passing through zero”
Claim · model-written summary
Enantiomerically pure natural constituents have specific rotations greater than 10 units.
- Taxon
- Ageratina glabrataAgeratina glabratae1
- Outcome
- specific rotationse2
- Value
- greater than 10 unitse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“A methodology to determine the enantiomeric excess and the absolute configuration (AC) of natural epoxythymols was developed and tested using five constituents of Ageratina glabrata”
e2“enantiomerically pure natural constituents showed positive or negative specific rotations greater than 10 units”