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Example 28

Chemical Purity Determination by HPLC
Various HPLC conditions can be used to determine the chemical purity of the compounds disclosed herein. One such example is disclosed above in relation to the thermodynamic aqueous solubility studies. Another example is disclosed below.
HPLC Conditions:
- LC: Waters Alliance 2695 Separations Module, Waters 2996 PDA detector and Waters Empower 2 Software (Version 6.00)
- Column: Phenomenex Luna C18(2); 4.6×50 mm; 3 μm
- Flow rate: 1.2 mL/min
- Injection Volume: 10 μL
- Mobile phase: Solvent A: 95% Water with 5% Methanol and 10 mM Ammonium Acetate; pH˜5.3
- Gradient Solvent B: MeOH with 10 mM Ammonium Acetate hold at 0% B 3 min
  - 0-47% B 3-4 min
  - hold at 47% B 4-10 min
  - 47%-74% B 10-11 min
  - hold at 74% B 11-13.5 min
  - return to 0% B 13.5-13.6 min
  - hold at 0% B 13.6-15.5 min
Under these conditions, the purity of 4, R_P-4, and S_P-4 was determined to be ˜99.6, ˜99%, and ˜99.5%, respectively. It is noted that higher purities can be realized by optimizing the methods disclosed above.
Inspection of the XRPD diffractograms shows that the two crystalline single diastereoisomers gave clearly different XRPD patterns. Additionally, there was a clear difference in the melting point of the two crystalline diastereoisomers, with R_P-4 having a considerably higher onset than S_P-4 (136° C. vs. 94° C.).
Example 29Additional Separation Methods
The following SFC separation (conditions listed below) yielded adequate separation of a mixture of the diastereomers, R_P-4 and S_P-4.


Preparative Method:	Analytical Method:

Chiralpak AS-H (2 × 25 cm) SN# 07-8656	Chiralpak AS-H (25 ×
	0.46 cm)
20% methanol/CO₂(100 bar)	20% methanol/CO₂(100 bar)
50 ml/min, 220 nm.	3 ml/min, 220 nm.
Conc.: 260 mg/30 ml methanol,
inj vol.: 1.5 ml

The following SFC separation (conditions listed below) yielded adequate separation of a mixture of the diastereomers, R_P-4 and S_P-4.


Preparative Method:	Analytical Method:

Chiralpak IA(2 × 15 cm) 802091	Chiralpak IA(15 × 0.46 cm)
30% isopropanol(0.1% DEA)/CO₂,	40% methanol(DEA)/CO₂, 100 bar
100 bar
60 mL/min, 220 nm.	3 mL/min, 220 nm.
inj vol.: 2 mL, 20 mg/mL methanol

TABLE 16

Summary of results from the batch characterization of R_P-4, 4, and S_P-4.
Analysis	R_P-4	4	S_P-4

Proton NMR	Single diastereoisomer	1:1 Mixture of	Single diastereoisomer
		diastereoisomers
XRPD	Crystalline – different	Amorphous	Crystalline – different
DSC	from S_P-4	Endotherm; 59° C.	from R_P-4
	Endotherm; melt – 136° C.		Endotherm; melt – 94° C.
TGA	No wt loss,	No wt loss, decomposition	No wt loss,
	decomposition >240° C.	>240° C.	decomposition >240° C.
IR	See above	See above	See above
Aq Solubility	1.58	6.11	5.65
(mg · ml⁻¹)
HPLC Purity	96.9%	99.6%	99.5%
40° C./75% RH	No form change	Deliquescence inside 1.5 h	Deliquescence inside 4.5 h
25° C./53% RH	—	Deliquescence	No form change
GVS	Non-hygroscopic up to 90%	—	Non-hygroscopic up to 60%
	RH		RH

Aqueous solubility was determined by suspending a sufficient amount of compound in water to give a maximum final concentration of ≧10 mg.ml⁻¹of the parent free-form of the compound. The suspension was equilibrated at 25° C. for 24 hours then the pH was measured. The suspension was then filtered through a glass fiber C filter into a 96 well plate. The filtrate was then diluted by a factor of 101. Quantitation was by HPLC with reference to a standard solution of approximately 0.1 mg.ml⁻¹in DMSO. Different volumes of the standard, diluted and undiluted sample solutions were injected. The solubility was calculated using the peak areas determined by integration of the peak found at the same retention time as the principal peak in the standard injection.

TABLE 14

HPLC Method Parameters for Solubility Measurements


Type of method:	Reverse phase with gradient elution
Column:	Phenomenex Luna, C18 (2) 5 μm 50 × 4.6 mm
Column Temperature	25
(° C.):
Standard Injections (μl):	1, 2, 3, 5, 7, 10
Test Injections (μl):	1, 2, 3, 10, 20, 50
Detection:	260, 80
Wavelength,
Bandwidth (nm):
Flow Rate (ml · min⁻¹):	2
Phase A:	0.1% TFA in water
Phase B:	0.085% TFA in acetonitrile
	Time (min)	% Phase A	% Phase B
Timetable:	0.0	95	5
	1.0	80	20
	2.3	5	95
	3.3	5	95
	3.5	95	5
	4.4	95	5

[0306]

Analysis was performed under the above-noted conditions on an Agilent HP1100 series system equipped with a diode array detector and using ChemStation software vB.02.01-SR1.

TABLE 15

Aqueous solubility result for R_P-4, 4, and S_P-4.
	pH of Unfiltered
Sample ID	mixture	Solubility/mg · ml⁻¹	Comments

R_P-4	7.12	1.58	Suspension
4	7.03	6.11	Residual solid
S_P-4	6.88	5.65	Residual solid

FIG 1

Chemical structures of RBV, BOC, TVR, and VRT-127394. Shown are the chemical structures of the anti-HCV drugs RBV {1-[(2R,3R,4S,5R)-3,4-dihydroxy-5-(hydroxymethyl)oxolan-2-yl]-1,2,4-triazole-3-carboxamide)} (A), BOC {(1R,2S,5S)-N-(4-amino-1-cyclobutyl-3,4-dioxobutan-2-yl)-3-[(2S)-2(tertbutylcarbamoylamino)-3,3-dimethylbutanoyl]-6,6-dimethyl-3-azabicyclo[3.1.0]hexane-2-carboxamide} (B), TVR {(3S,3aS,6aR)-2-[(2S)-2-[[(2S)-2-cyclohexyl-2-(pyrazine-2-carbonylamino)acetyl]amino]-3,3-dimethylbutanoyl]-N-[(3S)-1-(cyclopropylamino)-1, 2-dioxohexan-3-yl]-3,3a,4,5,6,6a-hexahydro-1H-cyclopenta[c]pyrrole-3-carboxamide} (C), and VRT-127394 (R diastereoisomer of TVR) (D).

Blank plasma samples used for matrix effect (ME) assessment and for the preparation of calibration and control samples were obtained from citrated blood (1,850 × g, 10 min, +4°C, Beckman J6B centrifuge) collected from Vaquez disease patients on the occasion of their regular phlebotomy.

The blank plasma used for the preparation of the calibration and quality control (QC) samples was acidified with 10% FA (50 μl of 10% FA added to 950 μl of plasma). The acidification of plasma aims at preventing the conversion of TVR to its epimer VRT-127394 that occurs in vivo and in vitro. (Tibotec-Janssen, personal communication).

Equipment.The LC system used consisted of Rheos Allegro quaternary pumps equipped with an online degasser and an HTS PAL autosampler (CTC Analytics AG, Zwingen, Switzerland) controlled by Janeiro-CNS 1.1 software (Flux Instruments AG, Thermo Fischer Scientific Inc., Waltham, MA). Separations were done on a Hypercarb 3-μm column (2.1 mm ID by 100 mm; Thermo Fischer Scientific) placed in a column oven thermostat regulated at +80°C (HotDog 5090; ProLab GmbH, Reinach, Switzerland). The chromatographic system was coupled to a triple-stage quadrupole quantum mass spectrometer (Thermo Fischer Scientific) equipped with an electrospray ionization (ESI) Ion Max interface and operated with the Xcalibur software package (version 2.0; Thermo Fischer Scientific).

READ T……http://aac.asm.org/content/57/7/3147.full

READ

http://www.us.edu.pl/uniwersytet/jednostki/wydzialy/chemia/acta/ac14/zrodla/14_AC14.pdf

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2291777/

UPDATE………….DEC2015

SOFOSBUVIR

NEW PATENT WO2015188782,

(WO2015188782) METHOD FOR PREPARING SOFOSBUVIR

CHIA TAI TIANQING PHARMACEUTICAL GROUP CO., LTD [CN/CN]; No. 8 Julong North Rd., Xinpu District Lianyungang, Jiangsu 222006 (CN)

Sofosbuvir synthesis routes currently used include the following two methods:

https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2015188782&redirectedID=true

Preparation Example 1 sofosbuvir implementation

Step (a):

At 0 ℃, dichloro-phenyl phosphate (6.0g, 28.4mmol) in dry dichloromethane (30ml) and stirred added alanine isopropyl ester hydrochloride (4.8g, 28.4mmol), the mixture After stirring and cooling to -55 ℃, was slowly added dropwise triethylamine (6.5g, 64mmol) and dichloromethane (30ml) mixed solution, keeping the temperature during at -55 ℃, dropping was completed, stirring was continued for 60 minutes, after liters to -5 ℃ stirred for 2 hours, TLC monitored the reaction was complete. To remove triethylamine hydrochloride was filtered and the filtrate evaporated under reduced pressure to give compound 3-1 as a colorless oil (Sp / Rp = 1/1).

³¹ PNMR (CDCl ₃ , 300 Hz, H ₃ PO ₄ as internal standard): δ8.25 & 7.94 (1: 1);

¹ HNMR (CDCl ₃ , 300 MHz): δ7.39-7.34 (m, 2H), 7.27-7.18 (m, 3H), 5.10-5.02 (m, 1H), 4.51 (br, 1H), 4.11 (m, 1H ), 1.49 (d, 3H), 1.29-1.24 (m, 6H);

¹³ C NMR (CDCl ₃ , 300 MHz): δ172.1 (Rp), 196.3 (Sp), 129.8,129.6 (d), 125.9,120.5 (d), 69.7 (d), 50.7 (d), 21.6 (d), 20.4 (d).

Step (b):

At 5 ℃, the compound of formula 2 (5.20g, 20.0mmol) in dry THF (30ml) and stirred at t-butyl chloride (1.0M THF solution, 42ml, 42.0mmol). The reaction temperature was raised to 25 ℃, and the mixture was stirred for 30 minutes. After addition of lithium chloride (21.0mmol), was slowly added dropwise the compound 3-1 (approximately 28.4mmol) and THF (30ml) mixed solution, keeping the temperature during at 5 ℃. Bi drops, stirred for 15 hours. With aqueous 1N HCl (25ml) The reaction solution was quenched (HPLC assay Sp: Rp ratio of 4: 1). Toluene was added (100ml), temperature was raised to room temperature. The organic layer was washed with 1N HCl, water, 5% Na ₂ CO ₃ and washed with brine, dried over anhydrous magnesium sulfate, filtered, and the solvent was distilled off under reduced pressure to a solid, was added methylene chloride (20ml), stirred for 5 minutes plus isopropyl ether, stirring was continued for 2 hours, the precipitated solid was filtered off. The solid was dissolved by heating in dichloromethane (60ml), slowly cooled to room temperature and the precipitated crystalline solid. Repeat if necessary obtain pure crystalline sofosbuvir (2.6g, yield 25%, HPLC purity measured 98.8%).

³¹ PNMR (CDCl ₃ , 300 Hz, H ₃ PO ₄ as internal standard): δ3.54ppm;

¹³ C NMR (CDCl ₃ , 300 Hz): δ173.1 (d), 162.7 (s), 150.2 (d), 139.3 (d), 129.6 (q);

MS (M + H): 530.1.

Preparation of compounds of formula 2 shown in Example 3-2

(1) a nucleophilic reagent as NaSCN, the phase transfer catalyst is TBAB

The compound (product of Example 1, step (a)) is represented by the formula 3-1 is dissolved in dichloromethane (20ml) was added TBAB (2.8mmol), the NaSCN (35mmol) in water (2.0ml) was added dropwise It was added to the reaction solution. Dropping was completed, stirring was continued for 60 minutes, the solid was removed by filtration. The filtrate was washed with water, add MgSO ₄ dried for 24 hours. Filtered, and the filtrate was evaporated under reduced pressure, to obtain a compound of formula 3-2 as (where X = SCN).

¹ HNMR (CDCl ₃ , 500Hz): δ7.32-7.13 (m, 3H), 7.08-7.02 (m, 2H), 5.0-4.9 (m, 1H), 3.92 (m, 1H), 1.49 (m, 3H ), 1.23-1.17 (m, 6H);

³¹ PNMR (CDCl ₃ , 300 Hz, H ₃ PO ₄ internal standard): δ-18.16 / -18.26.

(2) nucleophile NaSCN, phase transfer catalyst is 18-crown-6 ether

The compound (product of Example 1, step (a)) is represented by the formula 3-1 is dissolved in ethyl acetate (20ml) was added 18-crown -6 (2.8mmol), the NaSCN (35mmol) was added to the above the reaction mixture. Dropping was completed, stirring was continued for 60 minutes, the solid was removed by filtration. The filtrate was washed with water, add MgSO ₄ dried for 24 hours. Filtered, and the filtrate was evaporated under reduced pressure, to obtain a compound of formula 3-2 as (where X = SCN).

(3) nucleophile NaSCN, phase transfer catalyst is TBAB and 18-crown-6

The compound (product of Example 1, step (a)) is represented by the formula 3-1 is dissolved in dichloromethane (20ml) was added TBAB (2.8mmol) and 18-crown -6 (2.8mmol), the NaSCN (35mmol) in water (2.0ml) was added to the reaction solution. Dropping was completed, stirring was continued for 60 minutes, the solid was removed by filtration. The filtrate was washed with water, add MgSO ₄ dried for 24 hours. Filtered, and the filtrate was evaporated under reduced pressure, to obtain a compound of formula 3-2 as (where X = SCN).

(4) nucleophile as NaN ₃ , phase transfer catalyst is TBAB

The compound (product of Example 1, step (a)) is represented by the formula 3-1 is dissolved in dichloromethane (20ml) was added TBAB (2.8mmol), the NaN ₃ (35 mmol) in water (2.0ml) solution of was added dropwise to the reaction solution. Dropping was completed, stirring was continued for 60 minutes, the solid was removed by filtration. The filtrate was washed with water, add MgSO ₄ dried for 24 hours. Filtered, and the filtrate was evaporated under reduced pressure, to obtain a compound of formula 3-2 as (where X = N ₃ ).

¹ HNMR (CDCl ₃ , 500Hz): δ7.30-7.33 (m, 2H), 7.27-7.21 (m, 3H), 5.10-5.05 (m, 1H), 4.12-4.00 (m, 1H), 1.43 (d , 3H), 1.28-1.17 (m, 6H);

³¹ PNMR- (CDCl ₃ , 300 Hz, H ₃ PO ₄ internal standard): δ2.04 / 2.19.

(5) the nucleophilic reagent is KCN, the phase transfer catalyst is TBAB

The compound was dissolved in methylene chloride as in formula 3-1 (20ml), was added TBAB (2.8mmol), the KCN (35mmol) in water (2.0ml) was added dropwise to the reaction solution. Dropping was completed, stirring was continued for 60 minutes, the solid was removed by filtration. The filtrate was washed with water, add MgSO ₄ dried for 24 hours. Filtered, and the filtrate was evaporated under reduced pressure to remove the solvent to give a compound as shown in Formula 3-2 (where X = CN).

¹ HNMR (CDCl ₃ , 300 Hz): δ7.22-7.13 (m, 3H), 7.09-7.02 (m, 2H), 5.01-4.95 (m, 1H), 4.08-3.93 (m, 1H), 1.43-1.35 (m, 3H), 1.20-1.17 (m, 6H);

³¹ PNMR (CDCl ₃ , 300 Hz, H ₃ PO ₄ internal standard): δ-2.71 / -2.93.

Preparation Example 3 sofosbuvir implementation

(1) X is SCN

Under 5 ℃, the compound (5.20g, 20.0mmol) as shown in Equation 2 in dry THF (30ml) in. T-butyl chloride was added with stirring (1.0M THF solution, 42ml, 42.0mmol). The reaction temperature was raised to 25 ℃, and the mixture was stirred for 30 minutes. After addition of lithium chloride (21.0mmol), was slowly added dropwise a compound of formula 3-2 (Preparation Example 2 28.4 mmol, obtained) and THF (30ml) mixed solution, keeping the temperature during at 5 ℃. After dropping was completed, the mixture was stirred for 15 hours. With aqueous 1N HCl (25ml) The reaction solution was quenched (HPLC assay Sp: Rp ratio of 6: 1). After further addition of toluene (100ml), temperature was raised to room temperature. The organic layer was washed with 1N HCl, water, 5% Na ₂ CO ₃ and washed with brine, dried over anhydrous magnesium sulfate, filtered, and the solvent was distilled off under reduced pressure to a solid, was added methylene chloride (20ml), stirred for 5 minutes plus isopropyl ether, stirring was continued for 2 hours, the precipitated solid was filtered off. The solid was dissolved by heating in dichloromethane (60ml), slowly cooled to room temperature and the precipitated crystalline solid. Repeat if necessary obtain pure crystalline sofosbuvir (3.6g, yield 34%, HPLC purity measured 98.7%).

¹ HNMR (CDCl ₃ , 300 MHz): [delta] 8.63 (s, 1H, NH), 7.46 (d, 1H, C6-H), 7.36 (t, 2H, O-aromatic), 7.18-7.24 (m, 3H, m, P-aromatic), 6.20-6.14 (d, 1H, Cl’-H), 5.70-5.68 (d, 1H, C5-H), 5.05-4.97 (m, 1H, CH- (CH ₃ ) ₂ ) , 4.57-4.41 (m, 2H, C5′-H2), 4.12-4.09 (d, 1H, C3′-H), 4.06-3.79 (m, 3H, C3′-OH, C4′-H, Ala-CH -CH ₃ ), 3.79 (s, 1H, Ala-NH), 1.44 (d, 3H, C2′-H3), 1.36-1.34 (d, 3H, Ala-CH ₃ ), 1.25-1.23 (t, 6H, CH- (CH ₃ ) ₂ );

P ³¹ NMR (CDCl ₃ , 300 Hz, H ₃ PO ₄ internal standard): δ3.56.

(2) X is N ₃

Under 5 ℃, the compound (5.20g, 20.0mmol) as shown in Equation 2 in dry THF (30ml) in. T-butyl chloride was added with stirring (1.0M THF solution, 42ml, 42.0mmol). The reaction temperature was raised to 25 ℃, and the mixture was stirred for 30 minutes. Was added lithium chloride (21.0mmol), was slowly added dropwise after the compound of formula 3-2 obtained in Preparation Example 2 (about 28.4 mmol) and THF (30ml) mixed solution, keeping the temperature during at 5 ℃. Bi drops, stirred for 15 hours. With aqueous 1N HCl (25ml) The reaction solution was quenched (HPLC assay Sp: Rp ratio of 7: 1). After further addition of toluene (100ml), temperature was raised to room temperature. The organic layer was washed with 1N HCl, water, 5% Na ₂ CO ₃ and washed with brine, dried over anhydrous magnesium sulfate, filtered, and the solvent was distilled off under reduced pressure to a solid, was added methylene chloride (20ml), stirred for 5 minutes plus isopropyl ether, stirring was continued for 2 hours, the precipitated solid was filtered off. The solid was dissolved by heating in dichloromethane (60ml), slowly cooled to room temperature and the precipitated crystalline solid. Repeat if necessary obtain pure crystalline sofosbuvir (4.2g, yield 40%, HPLC purity measured 98.8%).

P ³¹ NMR (CDCl ₃ , 300 Hz, H ₃ PO ₄ internal standard): δ3.56.

(3) X is CN

Under 5 ℃, the compound (5.20g, 20.0mmol) as shown in Equation 2 in dry THF (30ml) in. T-butyl chloride was added with stirring (1.0M THF solution, 42ml, 42.0mmol). The reaction temperature was raised to 25 ℃, and the mixture was stirred for 30 minutes. After addition of lithium chloride (21.0mmol), was slowly added dropwise a compound of formula 3-2 obtained in Preparation Example 2 (about 28.4 mmol) and THF (30ml) mixed solution, keeping the temperature during at 5 ℃. Bi drops, stirred for 15 hours. With aqueous 1N HCl (25ml) The reaction solution was quenched (HPLC assay Sp: Rp ratio of 6: 1). After further addition of toluene (100ml), temperature was raised to room temperature. The organic layer was washed with 1N HCl, water, 5% Na ₂ CO ₃ and washed with brine, dried over anhydrous magnesium sulfate, filtered, and the solvent was distilled off under reduced pressure to a solid, was added methylene chloride (20ml), stirred for 5 minutes plus isopropyl ether, stirring was continued for 2 hours, the precipitated solid was filtered off. The solid was dissolved by heating in dichloromethane (60ml), slowly cooled to room temperature and the precipitated crystalline solid. Repeat if necessary obtain pure crystalline sofosbuvir (4.02g, yield 40%, HPLC purity measured 98.8%).

P ³¹ NMR (CDCl ₃ , 300 Hz, H ₃ PO ₄ internal standard): δ3.56.

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