JPH0352854A - Protective reagent precursor and production thereof - Google Patents

Abstract

NEW MATERIAL:A compound expressed by formula I [R is t-butyl, t-amyl, allyl, 9-fluorenyl methyl, 1-adamantyl, bornyl or 2-(trimethyl silyl) ethyl, etc.]. EXAMPLE:A t-amyl(p-methylthiophenyl) carbonate. USE:Used as protective reagent precursor able to be changed to both active ester-type protective reagents of water-soluble and oil-soluble by one-step treatment. PREPARATION:A p-methylthiophenyl chloroformate expressed by formula II is reacted with alcohols expressed by the formula R-OH in dichloromethane solvent in the presence of pyridine at 0-40 deg.C to afford the compound expressed by formula I. The compound expressed by formula I is sulfonated with dimethyl sulfate to afford water-soluble protective reagent, or oxidized to convert to oil-soluble protective reagent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a protective reagent precursor and a method for producing the same. More specifically, the present invention relates to methylthiophenyl carbonate (hereinafter referred to as Roc-MS) represented by the general formula (I).
The present invention relates to a protective reagent precursor (abbreviated as P) and a method for producing the same.

RO-CO-0-GS-CHs (I) [wherein R is t-butyl group, t-amyl group, allyl group, 9-fluorenylmethyl group, 1-adamantyl group, porunyl group, isobornyl group, 2 -(trimethylsilyl)ethyl group, 2.2.2-}lichloroethyl group, 2-phenyl-2
-probyl group, 2-(p-biphenylyl)-2-probyl group. ] Further, the present invention provides Roc-
The present invention relates to p-methylthiophenyl chloroformate, which is an intermediate of MSP, and a method for producing the same.

Roc-MSP represented by the above general formula (I) can be sulfonated with dimethyl sulfate to produce the following general formula (
It can be a sulfonium compound represented by V).

[In the formula, R is the same as that in formula (I)] The above formula (
The sulfonium compound represented by V) has the ability to acylate the amino group of an amino acid in an aqueous solution and is an extremely useful protecting reagent.

That is, the sulfonium compound represented by formula (V) is a water-soluble protective reagent. Here, acyl means a group obtained by removing the hydroxyl group from a carbonic acid monoester.

Furthermore, Roc-MS represented by the above general formula (1)
P is oxidized with hydrogen peroxide to form the following formula (VI)
It can be converted to the sulfonyl compound represented by

? O-CD-0-C2/-so■-C}I. (V
I) [wherein R is the same as that in formula (I). ] This sulfonyl compound is also a useful protecting reagent that has the ability to acylate the amino group of an amino acid. The sulfonyl compound represented by formula (VI) is oil-soluble and is therefore an oil-soluble protective reagent.

Therefore, methylthiophenyl carbonate (Roc-MSP) represented by the above general formula (I) is an extremely important protective agent that can be converted into either a water-soluble or oil-soluble protective reagent by reacting with dimethyl sulfate or hydrogen peroxide. It is a reagent precursor.

[Prior art and its problems] Protecting groups for amino groups in peptide chemical synthesis include:
Urethane-type protecting groups, which have a high racemization suppressing effect, are often used. For example, t-butyloxycarbonyl group, 9
An example thereof is -fluorenylmethoxycarbonyl group. When protecting the amine group of an amino acid with these groups,
A method is used in which the corresponding chloroformate or azide compound is reacted with the amino acid.

However, some chloroformates include unstable compounds such as t-butyloxytriponyl chloride, which requires complicated handling operations. Furthermore, when chloroformate is used, there is a problem in that dipeptides, etc., which are two amino acids condensed together, are produced as by-products. On the other hand, azide compounds have problems such as explosion and are dangerous to handle.

Therefore, active ester type protecting reagents are preferably used as compounds that are stable and do not cause side reactions.

The active ester type protecting reagent is a carbonate ester capable of aminolysis reaction, and an example thereof is t-butyl (p-nitrophenyl) carbonate, which is a carbonate ester of t-butyl alcohol and p-nitrophenol.

Incidentally, N-hydroxysuccinimide, 2,6-dimethylpyrimidine-1-thiol, and the like are known as active esters other than p-nitrophenol. However, when an active ester of p-nitrophenol is used, the protected amino acid and p-nitrophenol produced after the reaction are both acidic substances, so complicated separation and purification operations are required. On the other hand, when an active ester of N-hydroxysuccinimide is used, there is no problem if the protected amino acid is an acidic substance because N-hydroxysuccinimide is relatively water-soluble, but when a basic amino acid is protected, Since the protected amino acid produced is an amphoteric substance, it becomes water-soluble, and the water solubility of N-hydroxysuccinimide becomes a problem.

That is, it is desirable to select a protection reagent appropriately depending on the type of amino acid. However, the protective reagent needs to be combined separately, and there is no known protective reagent precursor that can combine both water-soluble and oil-soluble forms from the same raw material.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors have developed an active ester type protective reagent precursor that can be converted into either water-soluble or oil-soluble protective reagents from the same raw material. I have done extensive research on this. As a result, we discovered carbonate esters represented by the general formula (1) and completed this research.

A water-soluble protective reagent can be obtained by sulfonating this carbonate ester with dimethyl sulfate, and an oil-soluble protective reagent can be obtained by oxidizing it. That is,
The present invention relates to a methylthiophenyl carbonate represented by the following general formula (I), which is a protective reagent precursor that can be converted into either a water-soluble or oil-soluble active ester type protective reagent.

RO-CD-0-◎S-CI. (I) [In the formula, R means the same as above] As a method for synthesizing the methylthiophenyl carbonate represented by the above general formula (1) in the present invention, it is represented by the following formula (II). p-methylthiophenylchloroformate (hereinafter referred to as CP
-MSP) and an alcohol represented by the following formula (III) (hereinafter sometimes simply referred to as alcohol) in the presence of pyridine in a dichloromethane solvent.

CI-CD-0-CI2>S-CH3 (II
)R-Of{ (III
) In the present invention, there is no particular restriction on the order in which the raw materials are added, but generally a dichloromethane solution of pyridine and alcohol is added dropwise to a dichloromethane solution of CF-MSP. A suitable reaction temperature is 0 to 40°C. The amount of dichloromethane as a solvent was determined by CF-MS.
0.5 to 3 rnl per mole of P is suitable.

After the reaction is completed, the hydrochloride of pyridine is removed by washing the reaction solution with water, and Roc-MSP can be obtained by distilling off dichloromethane from the organic layer.

Further, the desired Roc-MSP can be purified by recrystallizing with methanol, hexane, etc., if necessary.

An advantage of using pyridine as a base in this reaction is that if a base other than pyridine is used, the desired product may not be obtained in some reactions. By the way, t-
The present inventors have experienced that when triethylamine is used in the reaction of amyl alcohol and p-methylthiophenol, the desired t-amyl (p-methylthiophenyl) carbonate cannot be obtained at all.

Next, as a method for synthesizing CF-MSP, which is a raw material for Roc-MSP, phosgene and p-methylthiophenol represented by the following formula (IV) (hereinafter abbreviated as MSP-OH) are combined in the presence of pyridine as a base. Obtained by reacting.

HO-GS-CHs (IV) The reaction method is to add a dichloromethane solution of MSP-0}1 and pyridine to a dichloromethane solution containing 1.5 to 5 times the mole of phosgene, preferably 2 to 3 times the mole of MSP-OH. -30 to 10°C, preferably at -20 to 0°C.

The amount of dichloromethane used as a solvent is MSP-
It is preferably 0.1 to 10rn1, particularly preferably 0.5 to 3mj7 per mol of 011.

After the reaction is complete, excess phosgene and the solvent dichloromethane are distilled off, and a solvent such as hexane or petroleum ether that does not dissolve pyridine hydrochloride is added to the residue, followed by CP-MS.
P is dissolved and pyridine hydrochloride is filtered off. When hexane is distilled off from this filtrate, CP-MSP is obtained as an oil. Moreover, this CF-MSP can be purified by distillation under reduced pressure if necessary.

The advantage of using pyridine as a base in this CP-MSP synthesis is that there are fewer side reactions and a high yield of CP-MSP. CF-MS because the base is common
An example of this is that P can be used as it is in the next reaction without being isolated. That is, by replenishing the solvent and adding dropwise alcohol and pyridine to the CP-MSP reaction solution in which excess phosgene has been distilled off together with the solvent, especially carbon
Roc-MSP without performing the isolation operation of P-MSP
It is possible to continue to join together until the end.

Roc-MSP obtained as described above is a stable substance and can be stored at room temperature for several months without any problem. Depending on the type of amino acid to be protected, it can be sulfonylated or oxidized to sulfonylate and used as a protecting reagent.

[Example] Next, the present invention will be explained in more detail with reference to Examples.

Example 1 (Preparation of chloroformate) Put 600rnl of dichloromethane into a reaction flask, cool on ice, and add phosgene 6.
4 ml (99 g 1, Omol) was introduced. Add 39% of pyridine to this solution. 55g (0.5mol) and p
-Methylthiophenol70. 10g (0.5mo
00 methane 100m7 including l>! The solution was added dropwise so that the reaction temperature did not rise above 5°C. After the dripping is finished,
The mixture was stirred for 1 hour under water cooling. Next, a distillation device was attached to the flask and heated in a 50° C. hot water bath to distill off excess phosgene and a portion of the solvent. Finally, the remaining solvent was removed under reduced pressure. Add 700mj of hexane to the resulting residue! was added and stirred for 1 hour at room temperature.

The precipitated pyridine hydrochloride was filtered off, and the filtrate was concentrated using an evaporator. Finally, the hexane is completely removed under vacuum, leaving crude p-methylthiophenyl chloroformate as an oil with a concentration of 101. 5g was obtained. The purity of this product was found to be 96.6% as a result of chlorine content and high performance liquid chromatography analysis, and the yield after purity correction was 97%. The impurities contained were mainly residual hexane, and bis(p-methylthiophenyl) carbonate was less than 0.4%.

Next, this crude p-methylthiophenyl chloroformate was purified by vacuum distillation, yielding 86.02 g (85% yield) of pure p-methylthiophenyl chloroformate.

Boiling point: 96.0 ~ 98.5℃ (0.3mmH
g) I R (NaC1): 1790 cm-'(C
=0) Elemental analysis value Theoretical value Actual value C: 47
, 41%; 47.48%1: 148%;
3.31%ct: 17.49%; 17
．． 36% Comparative Example 1 The same procedure as in Example 1 was carried out except that triethyl Jl4 amine was used instead of pyridine. The resulting crude p-methylthiophenyl chloroformate had a low purity of 72.2% and contained 26% bis(p-methylthiophenyl) carbonate. Moreover, when this crude product is purified by distillation, the yield is 53. 9 g, and the yield was low at 53%.

Example 2 (Combination of carbonic esters) Dichloromethane 100 and p-methylthiophenylchloroformate 20, which were combined in the same manner as in Example 1. 2
Put 7 g (0.1 mol) into a flask, and add 8.0 g (0.1 mol) of t-amyl alcohol to this solution. 15g (0.1mol)
and 50 mjl of methane solution containing 8.70 g (0. llmol) of pyridine! was added dropwise at room temperature, and then stirred for 2 hours. Pyridine hydrochloride was removed from the reaction solution by washing with water, and the organic layer was concentrated under reduced pressure. Finally, the supervitreous pyridine is removed under vacuum to obtain the target product t.
-Amyl(p-methylthiophenyl)carbonate was obtained as an oil in an amount of 5.09 g (yield: 100%).

q, J=7Hz, t-Am) s, S-Me) (4tl, m, OQS) 187 (2H, 2.42 (3H, 6.95-7.40 I R (NaC1): 1755 cm-' ( C=
0) Elemental analysis value Theoretical value Actual value C: 61
．． 39X; 61.05%1: 7.13%
．． 7.28% Comparative Example 2 The same procedure as in Example 2 was carried out except that triethylamine was used instead of pyridine.

As a result, the target product, t-amyl (p-methylthiophenyl) carbonate, was not obtained at all, but a substance that was thought to be a reaction between p-methylthiophenyl chloroformate and triethylamine was obtained.

Examples 3 to 8 The same procedure as in Example 2 was carried out except that the alcohol shown in Table 1 was used instead of t-amyl alcohol.

In addition, when the raw bottom material was a crystal, it was purified by recrystallization from methanol.

The results are summarized in Table 1, and the physical property values of each substance are shown in Table 2.

Example 9 p-methylthiophenyl chloroformate was combined with dichloromethane iooy in the same manner as in Example 1. 20. 2
Put 7g (0.111101) into a flask and add 13.2-phenyl-2-propyl alcohol to this solution.
62 g (0.1 mo 1) and pyridine 8. 70g
(0. llmol) in dichloromethane solution containing 50
rnI! was added dropwise under ice-cooling, and the mixture was stirred for 6 hours under water-cooling. After the reaction was completed, the reaction solution was poured into 200 mj2 of a 5% aqueous sodium carbonate solution. Wash the organic layer three times with water,
The organic layer was concentrated under reduced pressure.

Methanol was added to the residue and left in the refrigerator to crystallize.

The raw material was 2-phenyl-2-propyl (p-methylthiophenyl) carbonate, and the yield was 22.38 g (yield 74%). The physical property values are shown in Table 2.

Example 10 2 instead of 2-phenyl-2-probyl alcohol
- The same procedure as in Example 9 was performed except that (p-biphenylyl)-2-propyl alcohol was used.

The results are shown in Table 1 and the physical property values are shown in Table 2.

(The following is a blank space) Example 11 600 ml of dichloromethane was placed in a reaction flask, cooled on ice, and 64 ml (99 g, 1.0 mol) of phosgene was introduced. Add 39% of pyridine to this solution. 55g (0.5mo
l) and p-methylthiophenol70. 10g (0
．． A solution of 100 rnl of dichloromethane containing 5 mol) was added dropwise so that the reaction temperature did not rise above 5°C. After the dropwise addition was completed, the mixture was stirred for 1 hour under water cooling. Next, a distillation device was attached to the flask and heated in a 50° C. hot water bath to distill off excess phosgene and a portion of the solvent.

Heating was stopped when the volume of distilled liquid reached approximately 500 ml. In this way, a solution of p-methylthiophenylchloroformate was obtained.

Next, 500-g dichloromethane was added to this solution, cooled again on ice, and 17.79 g (0.
6 mol) and pyridine 47. 46g (0.6mo
A solution of 100 mj2 of dichloromethane containing 1) was added dropwise. After the dropwise addition was completed, stirring was continued at room temperature for 3 hours.

After the reaction was completed, the reaction solution was washed three times with water to remove pyridine hydrochloride, and the organic layer was dried over sodium sulfate. From this organic layer, dichloromethane, unreacted t-butyl alcohol and pyridine were distilled off under reduced pressure. Methanol was added to the obtained residue and the mixture was left in a refrigerator to obtain the target product, t-butyl (p-methylthiophenyl) carbonate, as crystals. The yield is 112. 68
g, and the yield was 94%.

Melting point: 54.5-55.5°C 6.95-. 7.40 (4H, m, O-O-S
) I R (KBr): 1750cm-' (
C=0) Elemental analysis value Theoretical value Actual value C: 59.97%; 59.49%1: 6.
71%. 6.65% Example 12 (Synthesis of water-soluble protective reagent) t-Butyl (p-methylthiophenyl) carbonate synthesized in Example 112. 40g (10
mmol), potassium carbonate 1. 38g (10mm
Add 10-acetonitrile to 1), then add 12-dimethyl sulfate. 61 g (100 mmol) was added. This liquid was stirred at 60°C for 2 hours.

The reaction solution was cooled to room temperature, and potassium carbonate was filtered off. This potassium carbonate is washed with a small amount of acetonitrile,
This washing liquid and the previous filtrate were combined.

Ether was added to this solution as a poor solvent to crystallize the sulfonated raw bottom material.

The raw bottom material was t-butyl (p-dimethylsulfoniophyl) carbonate methyl sulfate.

The yield is 3. The amount was 59 g, and the yield was 97%.

Melting point: 118-121°C (decomp.
)I R (KBr): Elemental analysis value: 3.66 (3H, s, MeS04-)7
．． 39. 8.17 (4}1) (each d,
J=10Hz, O-o-S") 1760cm-
' (C=0) Theoretical value C: 45.89%; }1: 6.05%; Actual value 45. 68% 6.00% Example 13 (Protection of amine group with water-soluble protection reagent) Glycine 0.
75g (10mmol) and triethylamine 1.52
g (15 mmol 1) was added to 20 mj2 of water and dissolved at room temperature. 4. t-Butyl (p-dimethylsulfoniophenyl) carbonate methyl sulfate was added to this solution in the same manner as in Example 12. 40g (12mm'
o 1) was gradually added, and the mixture was stirred at room temperature for 8 hours.

This reaction solution was adjusted to pH=1 to 2 with citric acid, and the precipitated raw bottom material was extracted with ethyl acetate. Add this organic layer to 3 parts with water.
The organic layer was washed twice and dried over sodium sulfate.

After drying, the organic layer was concentrated under reduced pressure, and petroleum ether was added to crystallize the raw bottom. The raw bottom material was N-(t-butoxycarbonyl)glycine, and the yield was 1.73 g (yield 99%).

Melting point: 86.5-89℃ (literature value 87-89℃
) Example, 14 (Preparation of oil-soluble protecting reagent) t-Butyl (p-methylthiophenyl) carboner synthesized in Example 11} 14. 42 g (60 mmol 1) were dissolved in 100 d of acetone, 100 g (1.03 mo 1) of 35% hydrogen peroxide was added under water cooling, and the mixture was stirred at room temperature for 12 hours. After the reaction was completed, the reaction solution was poured into 500rrL of water and 300ml of ethyl acetate was added.
Extracted with l. The organic layer was washed with water, 5% aqueous sodium bicarbonate solution, and water in this order. The washed organic layer was dried over anhydrous sodium sulfate, and ethyl acetate was distilled off under reduced pressure. Methanol was added to the obtained residue and the mixture was left in a refrigerator to obtain crystals. The obtained crystals were t-butyl (p-methylsulfonylphenyl) carbonate, yield 15.61
g (yield 96%).

Melting point: 105.0-107. 0℃? ．． 36
7.94 (4H) (each d, J=9Hz, I R (KBr): 1745cm-' (C=
0) Elemental analysis values: Theoretical value C: 52.93%; H: 5.92%: Actual value 52. 83% 5.98%? o-so■) Example 15 (Protection of amino group with oil-soluble protecting reagent) Nrm-penzylhistidine 4. 91g (20mmo I) 4
t-Butyl (p-methylsulfonylphenyl)carbonate, which was dissolved in 20rrL of aqueous N-sodium hydroxide solution and synthesized in Example 14.6. 54g (24mm
o Add 20 ml of dioxane solution of 1) at room temperature,
Stir for hours. After the reaction was completed, the reaction solution was cooled on ice and adjusted to pH 2 with IN-hydrochloric acid. This solution was extracted three times with ethyl acetate to remove unreacted protective reagent and p-methylsulfonylphenol'i::. The separated aqueous layer was neutralized with IN-sodium hydroxide aqueous solution.

This aqueous layer was concentrated to dryness under reduced pressure and redissolved in 50 ml of water. This solution was adjusted to pH'5 with acetic acid. 4 and left in the refrigerator, the target product, N-(t-butyloxycarbonyl)-N''-benzylhistidine, crystallized.The yield of the target product was 6.15 g (yield: 89%). there were.

Melting point = 179-182°C (literature value 180-182°C) [
Effects of the Invention In the protective reagent precursor of the present invention, water-soluble or oil-soluble protective reagents can be freely combined from the same raw material as desired. Furthermore, by combining the protective reagent precursors of the present invention or by using pyridine as the base and dichloromethane as the solvent, the reaction can be performed in high yield without using unstable intermediates. Furthermore, by using pyridine as the base and dichloromethane as the solvent in the synthesis of p-methylthiophenylchloroformate, which is an intermediate, not only can the desired product be obtained in high yield, but also p-methylthiophenyl chloroformate can be obtained from the reaction solution. The phenyl chloroformate can be used in the subsequent synthesis of methylthiophenyl carbonate without isolation.

The protective reagent precursor of the present invention is a substance that is extremely easy to combine and is stable, and can be converted into a water-soluble or oil-soluble protective reagent through one-step treatment, and is extremely useful as a protective reagent precursor. It is.

Claims (4)

[Claims] (1) Methylthiophenyl carbonate represented by the following general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) [In the formula, R is t-butyl group, t-amyl group, allyl group,
9-fluorenylmethyl group, 1-adamantyl group, bornyl group, isobornyl group, 2-(trimethylsilyl)ethyl group, 2,2,2-trichloroethyl group, 2-phenyl-2-propyl group, 2-(p -biphenylyl)-2-
Any propyl group. ] (2) p-methylthiophenylchloroformate represented by the following formula (II). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) (3) The following general formula is characterized by reacting p-methylthiophenyl chloroformate represented by the following formula (II) with an alcohol represented by the following formula (III) in a dichloromethane solvent in the presence of pyridine. A method for producing a carbonate ester represented by (I). ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (III) [R in formulas (I) and (III) is a t-butyl group, a t-amyl group, an allyl group, a 9-fluorenylmethyl group, a 1-adamantyl group, a bornyl group, an isobornyl group,
2-(trimethylsilyl)ethyl group, 2,2,2-trichloroethyl group, 2-phenyl-2-propyl group, 2-
(p-biphenylyl)-2-propyl group. ] (4) p-methylthiophenylchloro represented by the following formula (II), characterized by reacting p-methylthiophenol represented by the following formula (IV) with phosgene in the presence of pyridine in a dichloromethane solvent. Method for producing formate. ▲There are mathematical formulas, chemical formulas, tables, etc.▼(II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼(IV)