Analysis method for estimating chemical structure of compound

Abstract

To provide an analysis method for estimating the chemical structure of a compound with which the structure of the C=C position on a carbon chain can be estimated even for a cyclic compound.SOLUTION: An analysis method for estimating the chemical structure of a compound includes: a) a pre-processing step of performing pre-processing on a target compound so that a cyclic compound has a linear shape; and b) a mass spectrometry step of irradiating ions of the compound after the pre-processing, with at least one selected from radicals having oxidizing ability, radicals having reducing ability, and ozone to dissociate the ions, and performing mass analysis of fragment ions generated thereby to collect mass information of the fragment ions, wherein information on the ions estimated in a specific fragment ion estimation step is used for estimating the structure of the compound.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an analytical method for deducing the chemical structure of a compound. [Background technology]

[0002] Low-molecular-weight organic compounds have diverse structures, and structural analysis of structural isomers with no difference in exact mass remains a challenging task. Patent No. 7147789 (Patent Document 1) discloses that the C=C position on a carbon chain can be assigned by irradiating precursor ions with at least one of a hydroxyl radical and an oxygen radical (OAD: Oxygen Attachment Dissociation). There are many different types of C=C position isomers in living organisms and natural products, and assigning their positions is similarly difficult using conventional techniques. However, OAD allows for rapid structural estimation of the C=C position on a carbon chain, such as in fatty acids. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7147789 Summary of the Invention [Problem to be solved by the invention]

[0004] OAD specifically cleaves linear C=C bonds found in complex lipids and fatty acids, but in cyclic carbon chains such as those shown below, even if the double bond is cleaved by OAD, no fragment ions indicating the C=C position are observed, making it impossible to assign the C=C position. The compound below is called isoambrettolide (CAS: 28645-51-4), and indicates that a ketone exists at the second carbon (C2) and a C=C exists at the tenth carbon (C10).

[0005] [ka]

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide an analytical method for predicting the chemical structure of a compound, which enables structural prediction of the C=C position on the carbon chain even for cyclic compounds. [Means for solving the problem]

[0007] A first aspect of the present invention is An analytical method for estimating the chemical structure of a compound, comprising: a) a pretreatment step of pretreating a target compound so that a cyclic compound is converted into a linear compound; b) a mass analysis step of irradiating the pre-treated compound ions with at least one selected from oxidizing radicals, reducing radicals, and ozone to dissociate the ions, and performing mass analysis on the fragment ions thus generated to collect mass information on the fragment ions; and utilizing information on the ions estimated in the specific fragment ion estimation step for estimating the structure of the compound. Regarding. [Effects of the Invention]

[0008] According to the present invention, it is possible to estimate the structure of the C=C position on the carbon chain even in the case of a cyclic compound. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1(a) is a diagram showing the double bond of isoambrettolide, an example of a model compound, and FIG. 1(b) is a diagram showing the cleavage of isoambrettolide after pretreatment. [Figure 2] Figures 2(a) and 2(b) are OAD spectra of the cleaved isoambrettolide after pretreatment, respectively. [Figure 3] FIG. 1 is a schematic diagram showing the cleavage of Habanolide after pretreatment. DETAILED DESCRIPTION OF THE INVENTION

[0010] In the method according to the present invention, first, a target compound is pretreated so as to convert a cyclic compound into a linear compound (pretreatment step). In the method according to the present invention, the target compound is a compound to be subjected to analysis for estimating its chemical structure, and may or may not be a cyclic compound.

[0011] The cyclic compound may be any known cyclic compound without any particular limitation, such as a cyclic ester (lactone), a cyclic amide (lactam), a cyclic alkene (cycloalkene), an aromatic ring (such as benzene), an epoxide, etc. Among these, the cyclic compound is preferably a cyclic ester, since the cyclic compound can be converted into a linear one by a relatively simple method such as hydrolysis.

[0012] The pretreatment for converting a cyclic compound into a linear one can be any conventionally known method, without particular limitation. Examples of such pretreatment include hydrolysis (for example, when the cyclic compound is a cyclic ester (converted into a carboxylic acid and an alcohol by hydrolysis), or when the cyclic compound is a cyclic amide (converted into a carboxylic acid and an amine by hydrolysis)), ozonolysis (for example, when the cyclic compound is a cyclic alkene (decomposed into an aldehyde, ketone, or the like by ozonolysis)), hydrogenation (when the cyclic compound is an aromatic ring (e.g., benzene) (converted into a saturated hydrocarbon (e.g., cyclohexane) by hydrogenation)), photochemical ring-opening (for example, when the cyclic compound is a cyclic alkene such as cyclobutene (opened by light energy and converted into a linear alkene)), acid-catalyzed ring-opening (for example, when the cyclic compound is an epoxide (opened in the presence of an acid catalyst and converted into a diol (an alcohol having two hydroxyl groups))), and base-catalyzed ring-opening (for example, when the cyclic compound is a cyclic ester or epoxide (opened by the action of a base and converted into an alcohol or a carboxylic acid salt, respectively)). Among these, hydrolysis is preferred as the pretreatment, since it is a relatively simple method by which a cyclic compound can be converted into a linear compound.

[0013] Figure 1(a) shows the double bond of isoambrettolide (CAS: 28645-51-4), an example of a model compound, and Figure 1(b) shows a schematic diagram of the cleavage of isoambrettolide after pretreatment. It has a cyclic carbon chain structure with C=C (shaded area in Figure 1(a)), and no fragment ions are observed even when the C=C is cleaved by OAD.

[0014] The inventors performed the following steps: (1) Weigh out 1 mmol of the sample (isoambrettolide) and dissolve it in THF (10 mL). (2) Add 10 mL of 1N NaOH. (3) Stir at 35°C (about 1 hour). (4) Add 5 mL of hexane and stir. (5) Dispense 1 mL of the supernatant and evaporate to dryness using nitrogen. (6) Reconstitute in 1 mL of IPA 5 mM ammonium acetate + 10 nM EDTA (mobile phase B). In this way, hydrolysis of isoambrettolide was carried out.

[0015] In the method according to the present invention, the pretreated compound ions are irradiated with at least one selected from oxidizing radicals, reducing radicals, and ozone to dissociate the ions, and the resulting fragment ions are subjected to mass analysis to collect mass information on the fragment ions (mass analysis step). This mass analysis step can be performed using an ion trap-TOF mass analyzer, as shown in FIG. 1 of Japanese Patent No. 7147789 (Patent Document 1), which includes, within a vacuum chamber maintained at a vacuum, an ion source for ionizing components in a sample, an ion trap for trapping the ions generated by the ion source using a radio-frequency electric field, a time-of-flight mass separator for separating the ions ejected from the ion trap according to their mass-to-charge ratios, and an ion detector for detecting the separated ions. The mass analysis step can also be performed using an ion trap-TOF mass analyzer, as shown in FIG. 1 of Japanese Patent No. 7147789 (Patent Document 1), which includes, within a vacuum chamber maintained at a vacuum, an ion source for ionizing components in a sample, an ion trap for trapping the ions generated by the ion source using a radio-frequency electric field, a time-of-flight mass separator for separating the ions ejected from the ion trap according to their mass-to-charge ratios, and an ion detector for detecting the separated ions. The ion trap-TOF mass analyzer further includes a radical generator / irradiator for irradiating precursor ions trapped in the ion trap with radicals to dissociate the ions trapped in the ion trap, an inert gas supply for supplying a predetermined type of inert gas into the ion trap, a trap voltage generator, a controller, and a data processor. Specific examples include the LCMS-8000 series (manufactured by Shimadzu Corporation) and the LCMS-9000 series (manufactured by Shimadzu Corporation), but the present invention is not limited to these.

[0016] Examples of radicals with oxidizing ability include at least one of hydroxyl radicals, oxygen radicals, and hydrogen radicals. Among these, hydrogen radicals have low selectivity for the dissociation position of precursor ions, so it is preferable to use hydroxyl radicals and / or oxygen radicals (i.e., OAD) as radicals with oxidizing ability. Examples of radicals with reducing ability include nitrogen radicals.

[0017] Alternatively, ozone may be irradiated onto the pre-treated compound ions to dissociate the ions. It is known that when ozone is introduced into an ion trap and reacted with unsaturated fatty acids, precursor ions derived from the unsaturated fatty acids selectively dissociate at the positions of unsaturated bonds. The structure of the hydrocarbon chain can be estimated from the mass of the product ions generated by dissociation of the precursor ions at the positions of unsaturated bonds.

[0018] Here, Figures 2(a) and 2(b) show the OAD spectra of the cleaved isoambrettolide after pretreatment (Figure 2(a) is the O3 composition filter, and Figure 2(b) is the O2 composition filter). As described above, the isoambrettolide hydrolyzed as a pretreatment becomes linear as shown in Figure 1(b). The ion (precursor ion) of this linear compound ([MH] - The ion was dissociated by irradiating the C═C double bond (C═C = 269.212218 Da) with, for example, hydroxyl radicals and / or oxygen radicals. Regarding the expected C═C position, dissociation peaks (specific OAD peaks indicating double bond positions) on both sides of the C═C were confirmed at m / z 183.102 (Figure 2(a)) and 141.092 (Figure 2(b)).

[0019] The present inventors also performed the same pretreatment (hydrolysis) and OAD analysis on Habanolide (CAS: 111879-80-2) having the following structure as another example of a model compound.

[0020] [ka]

[0021] The habanolide used was a mixture of 12-ene and 13-ene. As with isoambrettolide, no product ions indicating the C=C position were obtained before hydrolysis. However, by subjecting the hydrolyzed sample to OAD, the OAD product ions shown in the figure were obtained, making it possible to assign the C=C position.

[0022] Figure 3 is a schematic diagram showing the cleavage of habanolide after pretreatment. The linear compound ion (precursor ion) was dissociated by irradiating it with, for example, hydroxyl radicals and / or oxygen radicals. Regarding the expected C=C position, dissociation peaks (specific OAD peaks indicating the double bond position) on both sides of the C=C were confirmed at m / z 213.1488 and 227.1645.

[0023] As described above, because carbon chains have a repeating structure of carbon and hydrogen, structural analysis of the C=C position is difficult even with techniques such as NMR. The pretreatment process in the method of the present invention is relatively simple, and OAD operates simply by setting it on / off in the mass spectrometer's control software. By combining this simple pretreatment process with the OAD method, C=C position assignment can be easily performed even in cyclic compounds.

[0024] In the method according to the present invention, the mass analysis step may include irradiating ions of the target compound, which is not subjected to a pretreatment that converts cyclic compounds into linear compounds, with at least one selected from an oxidizing radical, a reducing radical, and ozone to dissociate the ions, and performing mass analysis on the fragment ions thus generated to collect mass information on the fragment ions, and comparing the obtained spectra to determine whether the target compound is a cyclic compound. This makes it possible to determine whether the target compound is a cyclic compound.

[0025] [Aspect] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0026] (Section 1) An analytical method for estimating the chemical structure of a compound according to one embodiment includes the steps of: a) a pretreatment step of pretreating a target compound so that a cyclic compound is converted into a linear compound; b) a mass analysis step of irradiating the pre-treated compound ions with at least one selected from oxidizing radicals, reducing radicals, and ozone to dissociate the ions, and performing mass analysis on the fragment ions thus generated to collect mass information on the fragment ions; The information on the ions estimated in the specific fragment ion estimation step is used to estimate the structure of the compound.

[0027] According to the method described in Section 1, it is possible to estimate the structure of the C=C position on the carbon chain even for cyclic compounds.

[0028] (Section 2) In the method according to item 1, the pretreatment is hydrolysis of a cyclic compound.

[0029] According to the method described in item 2, a cyclic compound can be made linear by a relatively simple method.

[0030] (Section 3) Item 1, wherein the cyclic compound is a cyclic ester.

[0031] According to the method described in Section 3, it is possible to estimate the structure of the C=C position on the carbon chain even for cyclic esters.

[0032] (Section 4) In the method according to item 1, the ions of the pretreated compound are irradiated with at least one of hydroxyl radicals and oxygen radicals as radicals having oxidizing ability.

[0033] According to the method described in Section 4, it is possible to estimate the structure of the C=C position on the carbon chain of a cyclic compound using OAD.

[0034] (Section 5) In the method according to item 1, the mass analysis step includes irradiating ions of a compound of interest that has not been subjected to a pretreatment for converting a cyclic compound into a linear compound with at least one selected from an oxidizing radical, a reducing radical, and ozone to dissociate the ions, and performing mass analysis on the fragment ions thus generated to collect mass information on the fragment ions; By comparing the obtained spectra, it is possible to confirm whether the target compound is a cyclic compound or not.

[0035] According to the method described in item 5, it becomes possible to determine whether or not a target compound is a cyclic compound.

Claims

1. An analytical method for estimating the chemical structure of a compound, comprising: a) a pretreatment step of subjecting a target compound to a pretreatment so as to convert a cyclic compound into a linear compound; b) a mass analysis step of irradiating the pre-treated compound ions with at least one selected from an oxidizing radical, a reducing radical, and ozone to dissociate the ions, and then performing mass analysis on the fragment ions thus generated to collect mass information on the fragment ions; and utilizing information on the ions estimated in the specific fragment ion estimation step for estimating the structure of the compound.

2. The method of claim 1 , wherein the pretreatment is hydrolysis of a cyclic compound.

3. The method of claim 1 , wherein the cyclic compound is a cyclic ester.

4. 2. The method according to claim 1, wherein the ions of the pretreated compound are irradiated with at least one of hydroxyl radicals and oxygen radicals as radicals having oxidizing ability.

5. the mass analysis step includes irradiating ions of a compound of interest that has not been subjected to a pretreatment for converting a cyclic compound into a linear compound with at least one selected from an oxidizing radical, a reducing radical, and ozone to dissociate the ions, and performing mass analysis on the fragment ions thus generated to collect mass information on the fragment ions; The method according to claim 1, wherein the obtained spectra are compared to confirm whether the target compound is a cyclic compound or not.

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