TECHNICAL FIELD

The present invention relates to a novel method for producing oligonucleotides.

BACKGROUND ART

The forefront biotechnological researches such as genome-based drug discovery, and gene diagnosis and treatment have undergone rapid progress and development. Associated with that, oligonucleotides such as DNA probes, siRNA, antisense DNA and antisense RNA have been actively used recently. Some known chemical methods for the synthesis of oligonucleotides are phosphoramidite method and H-phosphonate method.

In the phosphoramidite method, a typical amidite reagent such as 2-cyanoethyl chloro(diisopropylamino)phosphinite or 2-cyanoethyl bis(diisopropylamino)phosphinite is used. These reagents are very expensive, and the isolation of an amidite compound entails complicated operations such as column purification and reprecipitation at an ultralow temperature. Further, amidite compounds are instable and need to be stored at −20° C.

On the other hand, the H-phosphonate method uses, among others, diphenyl phosphite or phosphorous acid that is a typical H-phosphonate reagent. These reagents are inexpensive, but complicated operations such as column purification are indispensable to the isolation of H-phosphonate compounds. H-phosphonate compounds need to be stored at 0° C. because of their stability (see, for example, Non Patent Literature 1).

Currently, a solid-phase synthesis process by phosphoramidite method has been increasingly optimized and automated. Thus, the solid-phase synthesis process by phosphoramidite method is advantageous in speed and is used most widely. However, the solid-phase synthesis process has drawbacks in that the scaling up of the process is limited for facility reasons, that the process involves excessive amounts of reagents and raw materials, and that it is difficult, for example, to know the status of the progress of the reaction in midstream and to analyze the structure of an intermediate.

In recent years, a liquid-phase synthesis process by H-phosphonate method using a pseudo solid phase-protecting group has been studied. Specifically, synthesis processes have been reported which use polyethylene glycol (MPEG) (see, for example, Patent Literature 1) or a long-chain hydrocarbon-containing group (see, for example, Patent Literature 2) as a pseudo solid phase-protecting group.

CITATION LIST
Patent Literature

Patent Literature 1: WO 2014/017615

Patent Literature 2: WO 2014/077292

Non Patent Literature

Non Patent Literature 1: Protocols for Oligonucleotides and Analogs, Humana Press (1993), pp. 44-73

SUMMARY OF INVENTION
Technical Problem

In the synthesis processes using polyethylene glycol (MPEG), examples of synthesis of up to 21-mer oligonucleotides have been presented, but GPC column purification is necessary for every elongation cycles. In the production processes using a long-chain hydrocarbon-containing group, examples of synthesis of 5-mer oligonucleotides have been presented, but a deprotection step results in a low yield.

As described above, the chemical processes for the synthesis of oligonucleotides using amidite compounds or H-phosphonate compounds have drawbacks in isolation operability and compound stability. There has been a demand for a novel oligonucleotide production method which is adaptable to mass synthesis.

An object of the present invention is to provide a novel method for producing an oligonucleotide using a nucleoside or oligonucleotide that is easy to isolate and has high storage stability.

Solution to Problem

To solve the problems discussed above, the present inventors carried out extensive studies. As a result, the present inventors have found that the problems can be solved by a production method which differs from a usual production method including a coupling step, a phosphorus atom modification step (such as oxidation reaction or sulfurization reaction) and a deprotection step, and which includes a step of subjecting to H-phosphonation a 5′-hydroxyl group or a 3′-hydroxyl group of a nucleoside or oligonucleotide having a pseudo solid phase-protecting group. The present invention has been completed based on the finding.

Aspects of the present invention include the following.

[1] A production method of an oligonucleotide including a step of subjecting a nucleoside or oligonucleotide having a pseudo solid phase-protecting group in at least one location selected from the group consisting of 2′-position, 3′-position, 5′-position and a nucleobase moiety and having a 5′-hydroxyl group or a 3′-hydroxyl group, to H-phosphonation to convert the 5′-hydroxyl group or the 3′-hydroxyl group into an H-phosphonated form.

[2] The production method described in [1], which includes at least one elongation reaction cycle including a step of subjecting a nucleoside or oligonucleotide having a pseudo solid phase-protecting group in at least one location selected from the group consisting of 2′-position, 3′-position, 5′-position and a nucleobase moiety and having a 5′-hydroxyl group or a 3′-hydroxyl group, to H-phosphonation to convert the 5′-hydroxyl group or the 3′-hydroxyl group into an H-phosphonated form.

[3] The production method described in [2], wherein the elongation reaction cycle includes:

a first step including deprotecting a first nucleoside or first oligonucleotide having a pseudo solid phase-protecting group in at least one location selected from the group consisting of 2′-position, 3′-position and a nucleobase moiety, having a 3′-hydroxyl group protected with a basic protecting group or a pseudo solid phase-protecting group, and having a 5′-hydroxyl group protected with a temporary protecting group, to remove the temporary protecting group to form a 5′-hydroxyl group,

a second step including converting the resultant 5′-hydroxyl group into an H-phosphonated form using an H-phosphonate reagent, and

a third step of forming an oligomer of the first nucleoside or first oligonucleotide with a second nucleoside or second oligonucleotide having a 3′-hydroxyl group and having a 5′-hydroxyl group protected with a temporary protecting group, by forming a phosphite diester bond from the 5′-hydroxyl group, now converted to the H-phosphonated form, of the first nucleoside or first oligonucleotide and the 3′-hydroxyl group of the second nucleoside or second oligonucleotide.

[4] The production method described in [3], further including a fourth step including converting the phosphite diester bond of the oligomer into a phosphodiester bond, a thiophosphodiester bond, a boranophosphodiester bond, an aminophosphodiester bond, a phosphodiester bond protected with a basic protecting group, or a thiophosphodiester bond protected with a basic protecting group.

[5] The production method described in [3], further including a fourth step including converting the phosphite diester bond of the oligomer into a phosphodiester bond, a thiophosphodiester bond, a boranophosphodiester bond or an aminophosphodiester bond.

[6] The production method described in [4] or [5], further including a fifth step of adding a polar solvent to a reaction mixture obtained from at least one step selected from the group consisting of the first step to the fourth step to form a precipitate, and collecting the precipitate by solid liquid separation.

[7] The production method described in [6], wherein the polar solvent is an alcohol solvent with 1 to 6 carbon atoms or a nitrile solvent with 1 to 6 carbon atoms.

[8] The production method described in any one of [3] to [7], further including a sixth step of removing all of the basic protecting group, the temporary protecting group and the pseudo solid phase-protecting group.

[9] The production method described in any one of [3] to [8], wherein the first nucleoside or the first oligonucleotide has a hydroxyl group protected with a pseudo solid phase-protecting group at 3′-position.

[10] The production method described in any one of [3] to [9], wherein the third step uses the second nucleoside.

[11] The production method described in [2], wherein the elongation reaction cycle includes:

a seventh step including deprotecting a third nucleoside or third oligonucleotide having a pseudo solid phase-protecting group in at least one location selected from the group consisting of 2′-position, 5′-position and a nucleobase moiety, having a 5′-hydroxyl group protected with a basic protecting group or a pseudo solid phase-protecting group, and having a 3′-hydroxyl group protected with a temporary protecting group, to remove the temporary protecting group to form a 3′-hydroxyl group,

an eighth step including converting the resultant 3′-hydroxyl group into an H-phosphonated form using an H-phosphonate reagent, and

a ninth step of forming an oligomer of the third nucleoside or third oligonucleotide with a fourth nucleoside or fourth oligonucleotide having a 5′-hydroxyl group and having a 3′-hydroxyl group protected with a temporary protecting group, by forming a phosphite diester bond from the 3′-hydroxyl group, now converted to the H-phosphonated form, of the third nucleoside or third oligonucleotide and the 5′-hydroxyl group of the fourth nucleoside or fourth oligonucleotide.

[12] The production method described in [11], further including a tenth step including converting the phosphite diester bond of the oligomer into a phosphodiester bond, a thiophosphodiester bond, a boranophosphodiester bond, an aminophosphodiester bond, a phosphodiester bond protected with a basic protecting group, or a thiophosphodiester bond protected with a basic protecting group.

[13] The production method described in [11], further including a tenth step including converting the phosphite diester bond of the oligomer into a phosphodiester bond, a thiophosphodiester bond, a boranophosphodiester bond or an aminophosphodiester bond.

[14] The production method described in [12] or [13], further including an eleventh step of adding a polar solvent to a reaction mixture obtained from any of the seventh step to the tenth step to form a precipitate, and collecting the precipitate by solid liquid separation.

[15] The production method described in [14], wherein the polar solvent is an alcohol solvent with 1 to 6 carbon atoms or a nitrile solvent with 1 to 6 carbon atoms.

[16] The production method described in any one of [11] to [15], further including a twelfth step of removing all of the basic protecting group, the temporary protecting group and the pseudo solid phase-protecting group.

[17] The production method described in any one of [11] to [16], wherein the third nucleoside or the third oligonucleotide has a hydroxyl group protected with a pseudo solid phase-protecting group at 5′-position.

[18] The production method described in any one of [11] to [17], wherein the ninth step uses the fourth nucleoside.

[19] The production method described in any one of [1] to [18], wherein the pseudo solid phase-protecting group is represented by the following formula (I):

[Image Omitted]

wherein * indicates a bond to a group protected by the pseudo solid phase-protecting group,

R¹is a C1-40 alkyl group, a C2-40 alkenyl group or a C2-40 alkynyl group, s is an integer of 1 to 5,

L¹is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L²is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —C(O)— or —O—,

L³is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L⁴is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —C(O)— or —O—,

L⁵is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group,

L⁶is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group,

m is 0 or 1, and

when the pseudo solid phase-protecting group is present in the nucleobase moiety and when m in the pseudo solid phase-protecting group is 0, the number of single bonds represented by L¹, L², L³and L⁴in the pseudo solid phase-protecting group is 0 to 3.

[20] The production method described in any one of [1] to [18], wherein the pseudo solid phase-protecting group is represented by the following formula (II):

[Image Omitted]

wherein * indicates a bond to a group protected by the pseudo solid phase-protecting group,

R¹is a C1-40 alkyl group, a C2-40 alkenyl group or a C2-40 alkynyl group, s is an integer of 1 to 5,

L¹is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L²is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group) or —O—,

L³is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L⁴is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group) or —O—, and

when the pseudo solid phase-protecting group is present in the nucleobase moiety, the number of single bonds represented by L¹, L², L³and L⁴in the pseudo solid phase-protecting group is 0 to 3.

[21] The production method described in any one of [3] to [20], wherein the temporary protecting group is a tert-butyldimethylsilyl group, a 4,4′-dimethoxytrityl group or a levulinyl group.

[22] The production method described in any one of [1] to [21], wherein the H-phosphonation step uses at least one H-phosphonate reagent selected from the group consisting of phosphorous acid, diphenyl phosphite, phenyl-H-phosphonate triethylammonium salt, p-toluyl-H-phosphonate triethylammonium salt, 2-chloro-4H-1,3,2-benzodioxaphosphorin-4-one and phosphorus trichloride.

[23] The production method described in any one of [1] to [22], wherein the nucleobases present in the nucleoside(s) and the oligonucleotide(s) are each independently at least one selected from the group consisting of 6-aminopurin-9-yl group (adenine residue), 2-amino-6-hydroxypurin-9-yl group (guanine residue), 2-oxo-4-amino-1,2-dihydropyrimidin-1-yl group (cytosine residue), 2-oxo-4-amino-5-methyl-1,2-dihydropyrimidin-1-yl group (5-methylcytosine residue), 2-oxo-4-hydroxy-1,2-dihydropyrimidin-1-yl group (uracil residue) and 2-oxo-4-hydroxy-5-methyl-1,2-dihydropyrimidin-1-yl group (thymine residue).

[24] A compound represented by the following formula (XI), or a salt thereof:

[Image Omitted]

wherein n is an integer of 1 or greater,

Base^Zindependently at each occurrence is a nucleobase, a nucleobase protected with a basic protecting group, or a nucleobase protected with a pseudo solid phase-protecting group,

X^Zindependently at each occurrence is a hydrogen atom, a halogen atom, a hydroxyl group, a hydroxyl group protected with a basic protecting group, an organic group bridged to the 4-carbon atom, or a hydroxyl group protected with a pseudo solid phase-protecting group,

Y independently at each occurrence is a hydrogen atom, a hydroxyl group, a hydroxyl group protected with a basic protecting group, a thiol group, a thiol group protected with a basic protecting group, a borohydride group, a mono-C1-6 alkylamino group or a di-C1-6 alkylamino group,

Z is a hydrogen atom, a basic protecting group, a temporary protecting group or a pseudo solid phase-protecting group, and

the compound or salt thereof satisfies at least one of that at least one Base^Zis a nucleobase protected with a pseudo solid phase-protecting group, that at least one X^Zis a hydroxyl group protected with a pseudo solid phase-protecting group, and that Z is a pseudo solid phase-protecting group.

[25] The compound or salt thereof described in [24], wherein the pseudo solid phase-protecting group is represented by the following formula (II):

[Image Omitted]

wherein * indicates a bond to a group protected by the pseudo solid phase-protecting group,

R¹is a C1-40 alkyl group, a C2-40 alkenyl group or a C2-40 alkynyl group, s is an integer of 1 to 5,

L¹is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L²is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group) or —O—,

L³is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L⁴is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group) or —O—, and

when the pseudo solid phase-protecting group is present in the nucleobase moiety, the number of single bonds represented by L¹, L², L³and L⁴in the pseudo solid phase-protecting group is 0 to 3.

[26] The compound or salt thereof described in [24] or [25], which satisfies at least one of that at least one Base^Zin the formula (XI) is a nucleobase protected with a pseudo solid phase-protecting group, and that Z is a pseudo solid phase-protecting group.

[27] The compound or salt thereof described in any one of [24] to [26], wherein Z in the formula (XI) is a pseudo solid phase-protecting group.

[28] The compound or salt thereof described in any one of [24] to [27], wherein n in the formula (XI) is 1 to 30.

[29] A compound represented by the following formula (XII), or a salt thereof:

[Image Omitted]

wherein

n is an integer of 1 or greater,

Base^Zindependently at each occurrence is a nucleobase, a nucleobase protected with a basic protecting group, or a nucleobase protected with a pseudo solid phase-protecting group,

X^Zindependently at each occurrence is a hydrogen atom, a halogen atom, a hydroxyl group, a hydroxyl group protected with a basic protecting group, an organic group bridged to the 4-carbon atom, or a hydroxyl group protected with a pseudo solid phase-protecting group,

Y independently at each occurrence is a hydrogen atom, a hydroxyl group, a hydroxyl group protected with a basic protecting group, a thiol group, a thiol group protected with a basic protecting group, a borohydride group, a mono-C1-6 alkylamino group or a di-C1-6 alkylamino group,

Z is a hydrogen atom, a basic protecting group, a temporary protecting group or a pseudo solid phase-protecting group, and

the compound or salt thereof satisfies at least one of that at least one Base^Zis a nucleobase protected with a pseudo solid phase-protecting group, that at least one X^Zis a hydroxyl group protected with a pseudo solid phase-protecting group, and that Z is a pseudo solid phase-protecting group.

[30] The compound or salt thereof described in [29], wherein the pseudo solid phase-protecting group is represented by the following formula (II):

[Image Omitted]

wherein * indicates a bond to a group protected by the pseudo solid phase-protecting group,

R¹is a C1-40 alkyl group, a C2-40 alkenyl group or a C2-40 alkynyl group, s is an integer of 1 to 5,

L¹is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L²is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group) or —O—,

L³is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L⁴is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group) or —O—, and

when the pseudo solid phase-protecting group is present in the nucleobase moiety, the number of single bonds represented by L¹, L², L³and L⁴in the pseudo solid phase-protecting group is 0 to 3.

[31] The compound or salt thereof described in [29] or [30], which satisfies at least one of that at least one Base^Zin the formula (XII) is a nucleobase protected with a pseudo solid phase-protecting group, and that Z is a pseudo solid phase-protecting group.

[32] The compound or salt thereof described in any one of [29] to [31], wherein Z in the formula (XII) is a pseudo solid phase-protecting group.

[33] The compound or salt thereof described in any one of [29] to [32], wherein n in the formula (XII) is 1 to 30.

[34] A compound represented by the following formula (XIII), or a salt thereof:

[Image Omitted]

wherein n is an integer of 1 or greater,

Base^Zindependently at each occurrence is a nucleobase, a nucleobase protected with a basic protecting group, or a nucleobase protected with a pseudo solid phase-protecting group,

X^Zindependently at each occurrence is a hydrogen atom, a halogen atom, a hydroxyl group, a hydroxyl group protected with a basic protecting group, an organic group bridged to the 4-carbon atom, or a hydroxyl group protected with a pseudo solid phase-protecting group,

W is a hydrogen atom or a temporary protecting group,

Y independently at each occurrence is a hydrogen atom, a hydroxyl group, a hydroxyl group protected with a basic protecting group, a thiol group, a thiol group protected with a basic protecting group, a borohydride group, a mono-C1-6 alkylamino group or a di-C1-6 alkylamino group,

Z is a hydrogen atom, a basic protecting group, a temporary protecting group or a pseudo solid phase-protecting group,

the compound or salt thereof satisfies at least one of that at least one Base^Zis a nucleobase protected with a pseudo solid phase-protecting group, that at least one X^Zis a hydroxyl group protected with a pseudo solid phase-protecting group, and that Z is a pseudo solid phase-protecting group, and

at least one of the pseudo solid phase-protecting groups is represented by the formula (I):

[Image Omitted]

wherein * indicates a bond to a group protected by the pseudo solid phase-protecting group,

R¹is a C1-40 alkyl group, a C2-40 alkenyl group or a C2-40 alkynyl group, s is an integer of 1 to 5,

L¹is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L²is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —C(O)— or —O—,

L³is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L⁴is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —C(O)— or —O—,

L⁵is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group,

L⁶is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group, and

m is 0 or 1 with the proviso that when m is 0, L⁴is not a single bond.

[35] A compound represented by the following formula (XIV), or a salt thereof:

[Image Omitted]

wherein

n is an integer of 1 or greater,

Base^Zindependently at each occurrence is a nucleobase, a nucleobase protected with a basic protecting group, or a nucleobase protected with a pseudo solid phase-protecting group,

X^Zindependently at each occurrence is a hydrogen atom, a halogen atom, a hydroxyl group, a hydroxyl group protected with a basic protecting group, an organic group bridged to the 4-carbon atom, or a hydroxyl group protected with a pseudo solid phase-protecting group,

W is a hydrogen atom or a temporary protecting group,

Y independently at each occurrence is a hydrogen atom, a hydroxyl group, a hydroxyl group protected with a basic protecting group, a thiol group, a thiol group protected with a basic protecting group, a borohydride group, a mono-C1-6 alkylamino group or a di-C1-6 alkylamino group,

Z is a hydrogen atom, a basic protecting group, a temporary protecting group or a pseudo solid phase-protecting group,

the compound or salt thereof satisfies at least one of that at least one Base^Zis a nucleobase protected with a pseudo solid phase-protecting group, that at least one X^Zis a hydroxyl group protected with a pseudo solid phase-protecting group, and that Z is a pseudo solid phase-protecting group, and

at least one of the pseudo solid phase-protecting groups is represented by the formula (I):

[Image Omitted]

wherein * indicates a bond to a group protected by the pseudo solid phase-protecting group,

R¹is a C1-40 alkyl group, a C2-40 alkenyl group or a C2-40 alkynyl group, s is an integer of 1 to 5,

L¹is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L²is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —C(O)— or —O—,

L³is a single bond, a C1-6 alkylene group, a C2-6 alkenylene group or a C2-6 alkynylene group,

L⁴is a single bond, —COO—, —CON(R²)— (wherein R²is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —OCO—, —N(R²)CO— (wherein R²is a hydrogen atom, a Cl-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group), —C(O)— or —O—,

L⁵is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group,

L⁶is a hydrogen atom, a C1-6 alkyl group, a C1-6 haloalkyl group, a C2-6 alkenyl group or a C2-6 haloalkenyl group, and

m is 0 or 1 with the proviso that when m is 0, L⁴is not a single bond.

[36] A pseudo solid phase-protecting group represented by the following formula (I):

[Image Omitted]

wherein * indicates a bond to at least one selected from the group consisting of 2′-, 3′- and 5′-hydroxyl groups and a nucleobase moiety of a nucleoside or oligonucleotide,