A method for selectively synthesizing 3,6′-dithiopomalidomide from pomalidomide

Abstract

The present invention relates to a method for selectively synthesizing 3,6'-dithiopomalidomide from pomalidomide. According to the present invention, the generation of byproduct 1,6-dithiopomalidomide is reduced during the synthesis of 3,6'-dithiopomalidomide, and the synthesis ratio of 3,6-dithiopomalidomide is selectively increased to more than 90%, thereby reducing the time and cost required for separating 1,6-dithiopomalidomide by HPLC or the like in the subsequent purification process, thereby having the advantages of improving the productivity and economy of 3,6'-dithiopomalidomide compounds.

Description

Technical Field

[0001] The present invention relates to a method for selectively synthesizing 3,6'-dithiopomalidomide from pomalidomide. Background Art

[0002] Pomalidomide (Pomalidomide, C 13 H 11 N3O4) is a drug in the thalidomide family of multiple myeloma therapeutic agents, used to treat relapsed and refractory multiple myeloma, and is also a drug being studied for the treatment of various cancers. Pomalidomide is an immunomodulator that can regulate the immune system to kill cancer cells, and is also an anti-angiogenesis inhibitor that inhibits the formation of blood vessels required for cancer growth.

[0003] The inventors found in the process of preparing various compounds based on pomalidomide and studying their pharmacological activities that 3,6′-dithiopomalidomide can be used to treat a variety of cancer diseases, and has fewer side effects and better effects than pomalidomide. Currently, research on the excellent anti-cancer effect of 3,6′-dithiopomalidomide is ongoing.

[0004] At the same time, the research team used the existing conventional Lawesson's reagent (IUPAC name: 2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphatidine-2,4-dithiol) in the process of preparing 3,6′-dithiopomalidomide from pomalidomide. Lawesson's reagent was introduced into organic chemical transformations in 1968 and used with a variety of reactants such as amides and ketones to carry out sulfidation reactions.

[0005] However, Lawesson's reagent has a variety of problems as a sulfurizing agent. For example, its thermal stability is unsatisfactory and it decomposes above 110°C. Moreover, Lawesson's reagent generally has low solubility and often requires the use of hexamethylphosphoramide (HMPA) as a solvent. HMPA is considered carcinogenic to humans and is banned in many countries. Other disadvantages of Lawesson's reagent are the strong unpleasant odor of the compound itself and the easy generation of by-products with a foul odor that are difficult to separate from the desired reaction product during the reaction.

[0006] In addition, when preparing dithiopomalidomide from pomalidomide using Lawesson's reagent, the yield is low and various byproducts and isomer 1,6-dithiopomalidomide exist as the main product, so there is a disadvantage that the purification process is more complicated. In particular, in this process, up to about 90% of 1,6'-dithiopomalidomide is produced together with 3,6'-dithiopomalidomide, so it is difficult to synthesize 3,6'-dithiopomalidomide with high purity, and there is a disadvantage that it takes a lot of time and cost to separate 1,6'-dithiopomalidomide.

[0007] Therefore, the problem of the synthesis method of pomalidomide using conventional Lawesson's reagent for the sulfidation reaction is that a high proportion of 1,6'-dithio-pomalidomide is generated, and the process efficiency is low, resulting in a low yield that is almost unusable for commercial use and an unacceptably high preparation cost. Therefore, there is a need in the art to develop a new method for selectively synthesizing high-purity 3,6'-dithio-pomalidomide from pomalidomide. Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] Therefore, the main object of the present invention is to provide a method for selectively synthesizing 3,6′-dithiopomalidomide from pomalidomide with high yield and low preparation cost that can be used for commercial purposes.

[0010] In addition, another object of the present invention is to provide a method for selectively synthesizing 3,6′-dithiopomalidomide from pomalidomide, thereby improving the yield of 3,6′-dithiopomalidomide and solving the problem that it takes a lot of time and cost to separate 1,6-dithiopomalidomide.

[0011] Other objects and advantages of the present invention will become more apparent from the following detailed description of the present invention, the claims and the accompanying drawings.

[0012] Technical solutions to the problem

[0013] According to one aspect of the present invention, a method for selectively synthesizing 3,6′-dithiopomalidomide from pomalidomide is provided, which comprises the following steps: a first step of adding a solvent to pomalidomide to dissolve it; a second step of adding phosphorous pentasulfide (P2S5) to the dissolved pomalidomide and stirring it; and a third step of removing and purifying the solid from the stirred solution.

[0014] In the synthesis method of 3,6′-dithiopomalidomide of the present invention, the solvent in the first step can be selected from any one of dioxane, toluene and tetrahydrofuran.

[0015] In the method for synthesizing 3,6′-dithiopomalidomide of the present invention, the dissolution in the first step can dissolve pomalidomide in the solvent at a concentration of 0.005 g / mL to 0.02 g / mL.

[0016] In the synthesis method of 3,6′-dithiopomalidomide of the present invention, the addition of phosphorus pentasulfide in the second step may be adding pomalidomide and phosphorus pentasulfide in a molar ratio of 1:1 to 1:2.5.

[0017] In the method for synthesizing 3,6′-dithiopomalidomide of the present invention, the stirring in the second step may be performed at 105° C. to 115° C. for 20 to 120 minutes.

[0018] Effects of the Invention

[0019] The present invention provides a method for selectively synthesizing 3,6′-dithiopomalidomide from pomalidomide, which has a high yield and low preparation cost that can be used for commercial purposes.

[0020] The method of the present invention can reduce the generation of the byproduct 1,6-dithiopomalidomide during the synthesis of 3,6′-dithiopomalidomide, and selectively increase the synthesis ratio of 3,6-dithiopomalidomide to more than 90%, thereby reducing the time and cost required for separating 1,6-dithiopomalidomide by HPLC in the subsequent purification process, thereby having the advantages of improving the productivity and economy of the 3,6′-dithiopomalidomide compound. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the chemical reactions during the synthesis of 3,6′-dithiopomalidomide from pomalidomide.

[0022] Figure 2 Schematic diagram of the synthesis of pomalidomide from 3-nitrophthalic anhydride and (2,6-dioxopiperidine-3-yl)amine trifluoroacetate.

[0023] Figure 3 The present invention is an analytical chart of the components of the reactants generated by the method for synthesizing 3,6′-dithiopomalidomide from pomalidomide through HPLC analysis.

[0024] Figure 4 Analytical chart of the components of the reactants generated by the method for synthesizing 3,6′-dithiopomalidomide from pomalidomide using conventional Lawesson's reagent after HPLC analysis. DETAILED DESCRIPTION

[0025] According to one aspect of the present invention, a method for selectively synthesizing 3,6′-dithiopomalidomide from pomalidomide is provided, comprising the following steps: a first step of adding a solvent to pomalidomide to dissolve it; a second step of adding phosphorous pentasulfide (P2S5) to the dissolved pomalidomide and stirring it; and a third step of removing and purifying solids from the stirred solution.

[0026] 3,6′-dithiopomalidomide (4-amino-2-(2-oxo-6-thiopyridin-3-yl)-3-thiopyridin-2,3-dihydro-1H-isoindol-1-one) synthesized by the method of the present invention Thiopomalidomide; 4-amino-2-(2-oxo-6-sulfanylidenepiperidin-3-yl)-3-sulfanylidene-2,3-dihydro-1H-isoindol-1-one) is a compound having the following [Chemical Formula 1], which can be synthesized from pomalidomide of the following [Chemical Formula 2]. In the process, an isomer of 1,6′-dithiopomalidomide (7-amino-2-(2-oxo-6-sulfanylidenepiperidin-3-yl)-3-sulfanylidene-2,3-dihydro-1H-isoindol-1-one) of the following [Chemical Formula 3] is simultaneously synthesized as a by-product.

[0027] [Chemical formula 1]

[0028]

[0029] [Chemical formula 2]

[0030]

[0031] [Chemical formula 3]

[0032]

[0033] The present inventors have attempted a method for synthesizing 3,6′-dithio-pomalidomide from pomalidomide using Lawesson's reagent. However, the method for synthesizing 3,6′-dithio-pomalidomide using Lawesson's reagent has a low yield, and multiple by-products and 1,6′-dithio-pomalidomide isomers are synthesized as the main compounds, so there is a disadvantage that it is difficult to separate and purify only a small amount of synthesized 3,6′-dithio-pomalidomide. This is because a separation device such as PREP-HPLC is used, and when 1,6′-dithio-pomalidomide is the main synthetic compound, it is impossible to use 3,6′-dithio-pomalidomide containing impurities in the interval of eluting 1,6′-dithio-pomalidomide and 3,6′-dithio-pomalidomide at the same time, which further reduces the yield.

[0034] In addition, a major problem encountered in the sulfidation reaction of pomalidomide using Lawesson's reagent is that Lawesson's reagent generally reacts at the most accessible position. That is, the 6' carbonyl group of the two sulfidation reaction sites for synthesizing 3,6'-dithiopomalidomide is prone to sulfidation. In contrast, the other 3' carboxyl group near aniline amine in phthalimide-imidecarbonyl has steric hindrance, which is difficult for the sulfiding agent to access, so the sulfidation reaction of the 1' carboxyl group is relatively preferential. Therefore, when Lawesson's reagent is used for sulfidation, the synthesis of 1,6'-dithiopomalidomide is significantly increased (at least 90% or more) compared with 3,6'-dithiopomalidomide.

[0035] In order to solve this problem, the present inventors have studied various sulfurization reactions that can preferentially carry out sulfurization reaction on the 3′-position carbonyl group of pomalidomide. In the process, it was confirmed that when phosphorous pentasulfide (P2S5) is used as a sulfurizing agent for pomalidomide, the steric hindrance of the 3′-position carbonyl group can be overcome, and the sulfurization reaction is preferentially carried out at the 3′-position, thereby confirming that 3,6′-dithiopomalidomide can be selectively generated from the two isomers of 3,6′-dithiopomalidomide and 1,6′-dithiopomalidomide.

[0036] See also Figure 1 The method for synthesizing 3,6′-dithio-pomalidomide from pomalidomide of the present invention is to synthesize 3,6′-dithio-pomalidomide by dropping phosphorous pentasulfide (P2S5) into pomalidomide dissolved in a solvent and stirring. In this process, among the two isomers of 3,6′-dithio-pomalidomide and 1,6′-dithio-pomalidomide, the yield of 3,6′-dithio-pomalidomide is more than 90%.

[0037] Meanwhile, the pomalidomide used in the present invention may be a commercially available compound, but pomalidomide produced by a direct synthesis method may also be used. In the case of direct synthesis, acetic acid (60.0 ml) is used as a solvent, and 3-nitrophthalic anhydride (3-nitr ophthalic anhydride) (1.5 g, 7.8 mmol) and (2,6-dioxopiperidine-3-yl)amine trifluoroacetate (1.9 g, 7.8 mmol) are stirred and reacted for 4.5 hours under a nitrogen atmosphere to produce 2-(2,6-dioxopiperidine-3-yl)-4-nitrophthalimide (2-(2,6-Dioxopiperidine-3-yl)-4-nitrophthalimide). de) compound, methanol (80.0 ml) was used as solvent, 2-(2,6-dioxopiperidine-3-yl)-4-nitrophthalimide (66.0 mg, 0.2 mmol) and activated carbon (activated carbon) supported palladium (10wt%, 45.0 mg) were reacted at room temperature for 7 hours under hydrogen atmosphere (44 lbs) and used directly for synthesis (reference Figure 2 ).

[0038] The sulfurizing agent phosphorus pentasulfide and the sulfurized compound pomalidomide in the first step can react in the liquid solvent medium of the sulfurizing agent. That is, the sulfurizing agent phosphorus pentasulfide and the sulfurized compound pomalidomide can be dissolved in a liquid solvent medium for use, and the solvent can use any one of the following solvents: dioxane, toluene and tetrahydrofuran. In a preferred embodiment of the present invention, dioxane is used as a solvent for the sulfurization reaction. After using solvents such as dioxane, toluene and tetrahydrofuran to react, after the reaction temperature drops to room temperature, a filter can be used to easily separate the residual salt produced by the decomposition of phosphorus pentasulfide from the sulfurized compound. Further purification of the reaction product can be carried out by, for example, selective recrystallization.

[0039] In the synthesis method of 3,6′-dithio-pomalidomide of the present invention, the dissolution in the first step can dissolve pomalidomide in a solvent at a concentration of 0.005 g / mL to 0.02 g / mL. The sulfiding agent phosphorus pentasulfide and the sulfiding compound pomalidomide react in a liquid solvent medium of the sulfiding agent, and preferably, the concentration of pomalidomide is adjusted so that it is fully dissolved in the solvent medium. In a preferred embodiment of the present invention, after 100 ml of the solvent dioxane is used to fully dissolve 1 g (3.66 mmol) of pomalidomide, the sulfiding agent phosphorus pentasulfide is added to react, and it can be confirmed that when the solvent of the above concentration is used, the conversion of 3,6′-dithio-pomalidomide reaches more than 90%.

[0040] In addition, in the synthesis method of 3,6′-dithio-pomalidomide of the present invention, the addition of phosphorus pentasulfide in the second step can be adding pomalidomide and phosphorus pentasulfide at a molar ratio of 1:1 to 1:2.5. The addition ratio of the sulfurizing agent phosphorus pentasulfide and the sulfurized compound pomalidomide affects the yield of the reaction product, because the number of carboxyl groups from pomalidomide sulfurized to 3,6′-dithio-pomalidomide is two, so it is ideal to add pomalidomide and phosphorus pentasulfide at a ratio of 1:2 for reaction. However, considering that various by-products are partially generated during the reaction, it is preferred to add the sulfurizing agent in a molar amount exceeding the sulfurized compound pomalidomide. Therefore, it is preferred that pomalidomide and phosphorus pentasulfide are added in a molar ratio of 1:1 to 1:2.5. When pomalidomide and phosphorus pentasulfide are added in a ratio lower than 1:1, the amount of phosphorus pentasulfide added as the sulfurizing agent is insufficient to fully perform the sulfurization reaction. When pomalidomide and phosphorus pentasulfide are added in a ratio exceeding 1:2.5, the added phosphorus pentasulfide causes an excessive sulfurization reaction, increasing the amount of by-products generated, thereby resulting in a lower yield of 3,6′-dithiopomalidomide.

[0041] In addition, in the synthesis method of 3,6′-dithio-pomalidomide of the present invention, the second step of adding phosphorus pentasulfide to the pomalidomide and stirring can be carried out at 105°C to 115°C for 20 minutes to 120 minutes. In the stirring step, when the reaction temperature is lower than 105°C, sufficient heat energy required for the reaction cannot be received, resulting in a disadvantage of lowering the yield of the 3,6′-dithio-pomalidomide compound. When the reaction temperature exceeds 115°C, the amount of by-products produced increases, resulting in a decrease in the yield of the 3,6′-dithio-pomalidomide compound. In addition, when the reaction time is less than 20 minutes, the sulfidation reaction cannot be fully carried out, resulting in a disadvantage of lowering the yield of the 3,6′-dithio-pomalidomide compound. When the reaction is carried out for more than 120 minutes, the reaction has been fully carried out, so there is a disadvantage of being uneconomical.

[0042] Next, the present invention will be described in more detail by way of examples. These examples are only used to illustrate the present invention, and it should not be understood that the scope of the present invention is limited to these examples.

[0043]

Experimental materials and analysis methods

[0044] The raw materials used in the experiment are shown in the following [Table 1].

[0045] [Table 1]

[0046]

[0047] NMR spectra were recorded at room temperature on a Bruker BioSpin 400 MHz (AVANC E III 400). The analytical samples were dissolved in DMSO-d6 and analyzed using an NMR tube (5-mm od, Wilmad, WG-1000-7). In addition, mass spectra were measured using a Waters SQ Detector 2 instrument operating in ESI (+) ionization mode.

[0048] HPLC analysis was performed using an Agilent 1100 series instrument.

[0049] Example 1. Pomalidomide: phosphorus pentasulfide = 1:2 (mol); react for 20 minutes

[0050] After adding dioxane (100 mL, 100 v / g) to pomalidomide (1 g, 3.66 mmol) to dissolve, phosphorus pentasulfide (P2S5) (1.63 g, 7.32 mmol) was added dropwise and stirred at 110°C for 20 minutes. After the reaction temperature was lowered to room temperature, the solid was immediately removed using a filter, and the solvent was concentrated under reduced pressure to obtain the reactant.

[0051] The results of HPLC and NMR analysis using 0.5 mg / mL of the reactant as a sample showed that the yield of the compound formed by combining 3,6′-dithiopomalidomide and 1,6′-dithiopomalidomide was 41%, and the ratio of the two was 98:2 (reference Figure 3 ).

[0052] 1H-NMR(DMSO-d6)d12.61(s,1H,NH),7.63(s,br,2H,NH2),7.47(t,J=7.6Hz,1H,C6-H),7.16(d,J=8.6Hz ,1H,C7-H),7.01(s,br,1H,C5-H),5.76(s,br,1H,C3′-H),3.20-2.80(m,3H) and 2.05-1.99(m,1H)ppm; 13C NMR(DMSO-d6)d 210.7, 194.4, 170.0, 167.5, 148.5, 135.3, 128.1, 124.2, 114.6, 112.2, 50.5, 41.5 and 24.0ppm; GCMS (CI / CH4), m / z 305 (M+)

[0053] In addition, all the reactants obtained by conducting the same reaction under the reaction conditions were purified using silica gel column chromatography (CHCl3: acetone = 100: 5). In this process, the 3,6'-dithiopomalidomide detection region overlapping with the 1,6'-dithiopomalidomide detection region was excluded, and only the pure 3,6'-dithiopomalidomide detection region was recovered, and 3,6'-dithiopomalidomide with a purity of 100% was purified. The separated 3,6'-dithiopomalidomide was solidified with DCM (20v / g) to obtain 3,6'-dithiopomalidomide (325mg, T0027-05) as an orange solid with a yield of 29.1%.

[0054] Example 2. Pomalidomide: phosphorus pentasulfide = 1:2 (mol); reaction for 60 minutes

[0055] After adding dioxane (100 mL, 100 v / g) to pomalidomide (1 g, 3.66 mmol) to dissolve, phosphorus pentasulfide (P2S5) (1.63 g, 7.32 mmol) was added dropwise and stirred at 110°C for 60 minutes. After the reaction temperature was lowered to room temperature, the solid was immediately removed using a filter, and the solvent was concentrated under reduced pressure to obtain the reactant.

[0056] HPLC analysis was performed using 0.5 mg / mL of the reactant as a sample. The yield of the combined compound of 3,6′-dithiopomalidomide and 1,6′-dithiopomalidomide was measured to be 19%, and the ratio of the two was measured to be 99:1.

[0057] Example 3. Pomalidomide: phosphorus pentasulfide = 1:2 (mol); reaction time 960 minutes

[0058] After adding dioxane (100 mL, 100 v / g) to pomalidomide (1 g, 3.66 mmol) to dissolve, phosphorus pentasulfide (P2S5) (1.63 g, 7.32 mmol) was added dropwise and stirred at 110°C for 960 minutes. After the reaction temperature was lowered to room temperature, the solid was immediately removed using a filter, and the solvent was concentrated under reduced pressure to obtain the reactant.

[0059] HPLC analysis was performed using 0.5 mg / mL of the reactant as a sample. The yield of the compound of 3,6′-dithiopomalidomide and 1,6′-dithiopomalidomide was measured to be 10%, and the ratio of the two was measured to be 99:1.

[0060] Example 4. Pomalidomide: phosphorus pentasulfide = 1:1 (mol); react for 30 minutes

[0061] After adding dioxane (100 mL, 100 v / g) to pomalidomide (1 g, 3.66 mmol) to dissolve, phosphorus pentasulfide (P2S5) (0.815 g, 3.66 mmol) was added dropwise and stirred at 110°C for 30 minutes. After the reaction temperature was lowered to room temperature, the solid was immediately removed using a filter, and the solvent was concentrated under reduced pressure to obtain the reactant.

[0062] As a result of HPLC analysis using 0.5 mg / mL of the reactant as a sample, the yield of the combined compound of 3,6′-dithiopomalidomide and 1,6′-dithiopomalidomide was measured to be 18%, and the ratio of the two was measured to be 91:9.

[0063] Example 5. Pomalidomide: phosphorus pentasulfide = 1:1 (mol); reaction for 60 minutes

[0064] After adding dioxane (100 mL, 100 v / g) to pomalidomide (1 g, 3.66 mmol) to dissolve, phosphorus pentasulfide (P2S5) (0.815 g, 3.66 mmol) was added dropwise and stirred at 110°C for 60 minutes. After the reaction temperature was lowered to room temperature, the solid was immediately removed using a filter, and the solvent was concentrated under reduced pressure to obtain the reactant.

[0065] HPLC analysis was performed using 0.5 mg / mL of the reactant as a sample. The yield of the combined compound of 3,6′-dithiopomalidomide and 1,6′-dithiopomalidomide was measured to be 28%, and the ratio of the two was measured to be 93:7.

[0066] Example 6. Pomalidomide: phosphorus pentasulfide = 1:1 (mol); reaction for 120 minutes

[0067] After adding dioxane (100 mL, 100 v / g) to pomalidomide (1 g, 3.66 mmol) to dissolve, phosphorus pentasulfide (P2S5) (0.815 g, 3.66 mmol) was added dropwise and stirred at 110°C for 120 minutes. After the reaction temperature was lowered to room temperature, the solid was immediately removed using a filter, and the solvent was concentrated under reduced pressure to obtain the reactant.

[0068] According to the results of HPLC analysis using 0.5 mg / mL of the reactant as a sample, the yield of the compound of 3,6′-dithiopomalidomide and 1,6′-dithiopomalidomide was measured to be 38%, and the ratio of the two was measured to be 94:6.

[0069] Comparative Example Synthesis of 3,6′-dithiopomalidomide using Lawesson's reagent

[0070] 3,6′-dithiopomalidomide was synthesized using the existing method using Lawesson's reagent synthesis.

[0071] Pomalidomide (100 mg, 0.366 mmol) and Lawesson's reagent (81.3 mg, 0.201 mmol) dissolved in anhydrous toluene (75 ml) were refluxed for 6 hours under nitrogen atmosphere. Then, Lawesson's reagent (162.6 mg, 0.402 mmol) was added and the reaction mixture was refluxed for 16 hours.

[0072] The results of HPLC and NMR analysis using 0.5 mg / mL of the reactant as a sample showed that the yield of the compound of 3,6′-dithiopomalidomide and 1,6′-dithiopomalidomide was 16.1%, and the ratio of the two was 10:90 (reference Figure 4 ).

[0073] The experimental results of the embodiments and comparative examples are summarized in the following [Table 2].

[0074] [Table 2]

[0075]

[0076] Referring to [Table 2], it can be confirmed that when pomalidomide and phosphorus pentasulfide are mixed and reacted without using Lawesson's reagent, the production ratio of 3,6′-dithiopomalidomide and 1,6′-dithiopomalidomide is such that 90% or more of 3,6′-dithiopomalidomide is produced, which is dominant, and thus the amount of 3,6′-dithiopomalidomide finally obtained in the subsequent purification process can be greatly increased.

[0077] With reference to the above detailed description and exemplary embodiments, those skilled in the art can implement the present invention within the full scope of the claims using routine experiments such as selectively performing the sulfurization reaction at the 3,6′-position among the 4 carboxyl groups present in the pomalidomide to be sulfurized. For example, the reaction can be carried out at normal pressure or in an inert atmosphere such as argon or nitrogen. Other parameters that can be optimized or changed are, for example, solvent medium, reaction temperature and reaction time, and all such modifications and variations are considered to be within the scope of the present invention.

Claims

1. A method for selectively synthesizing 3,6'-dithiopomalidomide from pomalidomide, characterized in that: The steps include: The first step is to add dioxane to pomalidomide to dissolve it; In the second step, phosphorus pentasulfide is added to the dissolved pomalidomide and stirred; In the third step, the solid is removed and purified from the stirred solution.

2. The method for selectively synthesizing 3,6'-dithiopomalidomide from pomalidomide according to claim 1, characterized in that: The first step, dissolving, is to dissolve pomalidomide in a solvent at a concentration of 0.005 g / mL to 0.02 g / mL.

3. The method for selectively synthesizing 3,6'-dithiopomalidomide from pomalidomide according to claim 1, characterized in that: In the second step, adding phosphorus pentasulfide is to add pomalidomide and phosphorus pentasulfide in a molar ratio of 1:1 to 1:2.

5.

4. The method for selectively synthesizing 3,6'-dithiopomalidomide from pomalidomide according to claim 1, characterized in that: In the second step, stirring is performed at 105° C. to 115° C. for 20 to 120 minutes.

Images