3,3-dimethyl-4-[(2-methylpropan-2-yl)oxy]-4-oxobutanoic acid

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of (1S,4S)-5-(2-(((1R,3aS,5aR,5bR,7aR,9S,11aR,11bR,13aR,13bR)-9-hydroxy-5a,5b,8,8,11a-pentamethyl-1-(prop-1-en-2-yl)icosahydro-1H-cyclopenta[a]chrysen-3a-yl)amino)ethyl)-2-thia-5-azabicyclo[2.2.1]heptane 2,2-dioxide (73 mg, 0.121 mmol) in DCM (2 mL) was added N,N-diisopropylethylamine (0.063 mL, 0.364 mmol), 4-(tert-butoxy)-3,3-dimethyl-4-oxobutanoic acid (49.1 mg, 0.243 mmol) (prepared as described in WO 2004014881), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (47.5 mg, 0.243 mmol) and 4-dimethylaminopyridine (29.7 mg, 0.243 mmol). The resulting solution mixture was stirred at rt. After 3.5 h, the reaction mixture was diluted with DCM (30 mL) and washed with 0.1N HCl (5 mL). The aqueous layer was extracted with DCM (25 mL). The combined organic layer was washed with 10% NaHCO3, brine, dried over MgSO4, filtered and concentrated. The crude material was purified by flash column chromatography (12 g, eluted with 97:3 DCM:MeOH) and dried under vacuum to give the title compound (83.2 mg, 87% yield) as a white solid. LC/MS: m/e 785.6 (M+H)+, 4.15 min (method 8). 1H NMR (400 MHz, CHLOROFORM-d) δ 4.71 (br. s., 1H), 4.59 (s, 1H), 4.48 (dd, J=10.6, 5.5 Hz, 1H), 3.89 (br. s., 1H), 3.51 (br. s., 1H), 3.40 (dd, J=13.0, 2.7 Hz, 1H), 3.27-3.21 (m, 1H), 3.20 (d, J=3.9 Hz, 1H), 2.90 (dd, J=13.1, 3.1 Hz, 1H), 2.86 (br. s., 1H), 2.74-2.60 (m, 1H), 2.53 (s, 3H), 2.51 (d, J=7.3 Hz, 2H), 2.41-2.32 (m, 1H), 2.02 (d, J=17.4 Hz, 1H), 1.86 (d, J=13.4 Hz, 1H), 1.82-1.73 (m, 2H), 1.68 (s, 3H), 1.66-1.50 (m, 7H), 1.43 (s, 11H), 1.42-1.30 (m, 6H), 1.26 (d, J=8.1 Hz, 2H), 1.23 (s, 3H), 1.22 (s, 3H), 1.12-1.04 (m, 2H), 1.01 (s, 3H), 0.95 (s, 3H), 0.84 (s, 6H), 0.83 (s, 3H), 0.78 (d, J=9.5 Hz, 1H). washed with 0.1N HCl (5 mL) The aqueous layer was extracted with DCM (25 mL) The combined organic layer was washed with 10% NaHCO3, brine dried over MgSO4 filtered concentrated The crude material was purified by flash column chromatography (12 g, eluted with 97:3 DCM:MeOH) dried under vacuum

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 4-tert-butoxy-3,3-dimethyl-4-oxobutanoic acid (1.174 g, 5.80 mmol), DMAP (0.709 g, 5.80 mmol) in DCM (20 mL) stirred at rt was added EDCl (1.854 g, 9.67 mmol). The reaction mixture was stirred at rt for 2 h. (E)-N—((S)-1-(3-Chlorophenyl)ethyl)-3-((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-9-hydroxy-1-isopropyl-5a,5b,8,8,11a-pentamethyl-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-3a-yl)acrylamide (1.2 g, 1.934 mmol) was added to the reaction mixture. The resultant mixture was stirred at rt overnight. Water was added and the mixture was partitioned and washed with additional water. The organics were dried over sodium sulfate filtered through a short silica gel column and evaporated in vacuo to give the crude product as yellow foam. This material was used in the next step without further purification. was added to the reaction mixture the mixture was partitioned washed with additional water The organics were dried over sodium sulfate filtered through a short silica gel column evaporated in vacuo

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 4-tert-butoxy-3,3-dimethyl-4-oxobutanoic acid (1.174 g, 5.80 mmol), DMAP (0.709 g, 5.80 mmol) in DCM (20 mL) stirred at rt was added EDCl (1.854 g, 9.67 mmol). The reaction mixture was stirred at rt for 2 h. (E)-N—((S)-1-(3-Chlorophenyl)ethyl)-3-((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-9-hydroxy-1-isopropyl-5a,5b,8,8,11a-pentamethyl-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-3a-yl)acrylamide (1.2 g, 1.934 mmol) was added to the reaction mixture. The resultant mixture was stirred at rt overnight. Water was added and the mixture was partitioned and washed with additional water. The organics were dried over sodium sulfate filtered through a short silica gel column and evaporated in vacuo to give the crude product as yellow foam. This material was used in the next step without further purification. was added to the reaction mixture the mixture was partitioned washed with additional water The organics were dried over sodium sulfate filtered through a short silica gel column evaporated in vacuo

Conditions: temp:20.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of DMAP (415 mg, 3.40 mmol), EDC (652 mg, 3.40 mmol) and 4-tert-butoxy-3,3-dimethyl-4-oxobutanoic acid (425 mg, 2.039 mmol) in DCM (10 mL) stirred at 20° C. for 30 min was added (E)-N-(1-(4-chlorophenyl)cyclopropyl)-3-((3aS,5aR,5bR,7aR,9S,11aR,11bR,13aS)-9-hydroxy-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-3a-yl)-2-methylacrylamide (650 mg, 0.680 mmol). The reaction mixture was stirred at 20° C. for 2 h. The mixture was washed with saturated ammonium chloride, water, and saturated NaHCO3, water and brine. The organic layer was dried over Na2SO4, filtered and concentrated to give the crude product, which was purified by silica gel column eluting with petroleum ether/Ethyl acetate (3:1) to afford 1-tert-butyl 4-((3aS,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-((E)-3-((1-(4-chlorophenyl)cyclopropyl)amino)-2-methyl-3-oxoprop-1-en-1-yl)-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl) 2,2-dimethylsuccinate (300 mg, 52%) as a light yellow solid. 1H NMR (400 MHz, CHLOROFORM-d) δ=7.30-7.22 (m, 2H), 7.22-7.14 (m, 2H), 6.59 (s, 1H), 6.32 (s, 1H), 4.51 (dd, J=5.4, 10.9 Hz, 1H), 3.28-3.10 (m, 1H), 2.72 (d, J=10.3 Hz, 1H), 2.55 (s, 3H), 2.41-2.21 (m, 2H), 2.12-0.71 (m, 61H). The mixture was washed with saturated ammonium chloride, water, and saturated NaHCO3, water and brine The organic layer was dried over Na2SO4 filtered concentrated to give the crude product, which was purified by silica gel column eluting with petroleum ether/Ethyl acetate (3:1)

Conditions: temp:25.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 4-(tert-butoxy)-3,3-dimethyl-4-oxobutanoic acid (122 mg, 0.604 mmol), DMAP (123 mg, 1.007 mmol) and EDC (193 mg, 1.007 mmol) in dichloromethane (12 mL) stirred at room temp for 30 min was added (E)-3-((3aS,5aR,5bR,7aR,9S,11aR,11bR,13aS)-9-hydroxy-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-3a-yl)acrylic acid (100 mg, 0.201 mmol). The reaction mixture was stirred at 25° C. for 3 h. The produce was extracted with DCM (15 mL*3), the combined organic phase was washed with brine (20 mL), dried, and the solvent removed under reduced pressure to give 110 mg of residue as light yellow solid which was used in the next reaction without further purification. The produce was extracted with DCM (15 mL*3) the combined organic phase was washed with brine (20 mL) dried the solvent removed under reduced pressure

Conditions: temp:20.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of DMAP (647 mg, 5.30 mmol), EDC (1016 mg, 5.30 mmol) and 4-tert-butoxy-3,3-dimethyl-4-oxobutanoic acid (663 mg, 3.18 mmol) (11) in Dichloromethane (10 mL) stirred at 20° C. for 30 min was added (E)-N-(1-(4-chlorophenyl)cyclopropyl)-3-((3aS,5aR,5bR,7aR,9S,11aR,11bR,13aS)-9-hydroxy-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-3a-yl)acrylamide (685 mg, 1.060 mmol). The reaction mixture was stirred at 20° C. for 2 h. The mixture was washed with saturated ammonium chloride, water, and saturated NaHCO3, water, and brine. The organic layer was dried over Na2SO4, filtered and concentrated to give the crude product, which was purified by silica gel column eluting with Petrol ether/Ethyl acetate (5:1) to afford the product 1-tert-butyl 4-((3aS,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-((E)-3-((1-(4-chlorophenyl)cyclopropyl)amino)-3-oxoprop-1-en-1-yl)-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl) 2,2-dimethylsuccinate (480 mg, 0.542 mmol, 51.2%) as a light yellow solid. The mixture was washed with saturated ammonium chloride, water, and saturated NaHCO3, water, and brine The organic layer was dried over Na2SO4 filtered concentrated to give the crude product, which was purified by silica gel column eluting with Petrol ether/Ethyl acetate (5:1)

Conditions: temp:20.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of DMAP (647 mg, 5.30 mmol), EDC (1016 mg, 5.30 mmol) and 4-tert-butoxy-3,3-dimethyl-4-oxobutanoic acid (663 mg, 3.18 mmol) (11) in Dichloromethane (10 mL) stirred at 20° C. for 30 min was added (E)-N-(1-(4-chlorophenyl)cyclopropyl)-3-((3aS,5aR,5bR,7aR,9S,11aR,11bR,13aS)-9-hydroxy-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-3a-yl)acrylamide (685 mg, 1.060 mmol). The reaction mixture was stirred at 20° C. for 2 h. The mixture was washed with saturated ammonium chloride, water, and saturated NaHCO3, water, and brine. The organic layer was dried over Na2SO4, filtered and concentrated to give the crude product, which was purified by silica gel column eluting with Petrol ether/Ethyl acetate (5:1) to afford the product 1-tert-butyl 4-((3aS,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-((E)-3-((1-(4-chlorophenyl)cyclopropyl)amino)-3-oxoprop-1-en-1-yl)-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl) 2,2-dimethylsuccinate (480 mg, 0.542 mmol, 51.2%) as a light yellow solid. The mixture was washed with saturated ammonium chloride, water, and saturated NaHCO3, water, and brine The organic layer was dried over Na2SO4 filtered concentrated to give the crude product, which was purified by silica gel column eluting with Petrol ether/Ethyl acetate (5:1)

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: (3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-9-Hydroxy-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysene-3a-carbaldehyde (26.9 g, 1 equiv), 4-(tert-butoxy)-3,3-dimethyl-4-oxobutanoic acid (14.96 g, 1.25 equiv) and THF (538 ml, 20 vol) were charged to a flask. Benzoyl chloride (10.4 g, 1.25 equiv) was added followed by slow addition of triethylamine (14.97 g, 2.5 equiv) forming a thick slurry. DMAP (0.1.81 g, 0.25 equiv) was added and the reaction was allowed to stir at ambient temperature for approximately 18 hours until complete by HPLC. Reaction was then charged with ethyl acetate (538 mL, 20 vol) and water (269 ml, 10 vol), stirred well and allowed to settle. Aqueous phase was removed and the organic phase washed with saturated sodium bicarbonate solution (2×10 vol) followed by water (269 mL, 10 vol). The reaction solution evaporated under vacuum to approximately 4 volumes to produce solids. Additional hexanes (269 ml, 10 vol) was added and reaction heated back to reflux to nearly form solution and slowly cooled to ambient temperature (seeding with desired product) and let stir for 15 minutes then cooled to 0° C. for approximately two hours and filtered solid. Washed solid with hexanes (2×10 vol) and dried at 50° C. under vacuum to a weight of 32.15 g, 85% yield of 1-tert-butyl 4-((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-formyl-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl) 2,2-dimethylsuccinate. forming a thick slurry Reaction stirred well Aqueous phase was removed the organic phase washed with saturated sodium bicarbonate solution (2×10 vol) The reaction solution evaporated under vacuum to approximately 4 volumes to produce solids reaction heated back to reflux to nearly form solution

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of 4-tert-butoxy-3,3-dimethyl-4-oxobutanoic acid 10 (119 mg, 0.587 mmol), 3-(1-(5-chloropyrimidin-2-yl)cyclopropyl)-5-((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-9-hydroxy-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-3a-yl)oxazolidin-2-one (108) (130 mg, 0.196 mmol), EDC (188 mg, 0.978 mmol) and DMAP (71.7 mg, 0.587 mmol) in DCM (5 mL) was stirred at rt overnight. After the reaction finished, the mixture was diluted with DCM (25 ml), washed with water (2×15 ml) and brine (20 ml), dried over sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by silica gel chromatography using petroleum ether/EtOAc (6:1 to 3:1) as eluent to give the two diastereomeric products 1-tert-butyl 4-((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-((S)-3-(1-(5-chloropyrimidin-2-yl)cyclopropyl)-2-oxooxazolidin-5-yl)-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl) 2,2-dimethylsuccinate (109) and 1-tert-butyl 4-((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-((R)-3-(1-(5-chloropyrimidin-2-yl)cyclopropyl)-2-oxooxazolidin-5-yl)-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl) 2,2-dimethylsuccinate (110) in the amounts of (80 mg, 45%) and (50 mg, 22%) as white solids. The stereochemical assignments for each diastereomer were not made. Compound A (tentatively designated as 109): LC/MS: m/z calculated 847.5. found 848.3 (M+1)+. Compound B (tentatively designated as 110): LC/MS: m/z calculated 847.5. found 848 (M+1)+. washed with water (2×15 ml) and brine (20 ml) dried over sodium sulfate filtered concentrated under reduced pressure The residue was purified by silica gel chromatography

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of 4-(tert-butoxy)-3,3-dimethyl-4-oxobutanoic acid (11.91 g, 58.9 mmol), N,N-dimethylpyridin-4-amine (4.50 g, 36.8 mmol) in DCM (20 mL) was added EDC (11.29 g, 58.9 mmol). The reaction mixture was stirred at rt for 1 h. Then, (3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-(2-((4-chlorobenzyl)(2-(dimethylamino)ethyl)amino)acetyl)-9-hydroxy-1-isopropyl-5a,5b,8,8,11a-pentamethyl-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-2-one (52) (5 g, 7.36 mmol) was add. Upon completion, the mixture was washed with 2 M HCl, water and brine. The organic layer was dried over Na2SO4, filtered and concentrated to give the crude product. The product was purified by a silica gel column using dichloromethane/methanol (20:1) to afford 1-tert-butyl 4-((3aR,5aR,5bR,7aR,9S,11aR,11bR,13aS)-3a-(2-((4-chlorobenzyl)(2-(dimethylamino)ethyl)amino)acetyl)-1-isopropyl-5a,5b,8,8,11a-pentamethyl-2-oxo-3,3a,4,5,5a,5b,6,7,7a,8,9,10,11,11a,11b,12,13,13a-octadecahydro-2H-cyclopenta[a]chrysen-9-yl) 2,2-dimethylsuccinate (53) (1.8 g, 1.917 mmol, 26.1% yield) as an oil. 1H NMR (400 MHz, CHLOROFORM-d) δ=7.27 (s, 4H), 4.60-4.39 (m, 1H), 3.82 (d, J=13.8 Hz, 1H), 3.59 (d, J=13.8 Hz, 1H), 3.50-3.05 (m, 3H), 2.82-2.63 (m, 2H), 2.63-0.53 (m, 67H). Upon completion, the mixture was washed with 2 M HCl, water and brine The organic layer was dried over Na2SO4 filtered concentrated to give the crude product The product was purified by a silica gel column

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of (1S,4S)-5-(2-(((1R,3aS,5aR,5bR,7aR,9S,11aR,11bR,13aR,13bR)-9-hydroxy-5a,5b,8,8,11a-pentamethyl-1-(prop-1-en-2-yl)icosahydro-1H-cyclopenta[a]chrysen-3a-yl)amino)ethyl)-2-thia-5-azabicyclo[2.2.1]heptane 2,2-dioxide (73 mg, 0.121 mmol) in DCM (2 mL) was added N,N-diisopropylethylamine (0.063 mL, 0.364 mmol), 4-(tert-butoxy)-3,3-dimethyl-4-oxobutanoic acid (49.1 mg, 0.243 mmol) (prepared as described in WO 2004014881), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (47.5 mg, 0.243 mmol) and 4-dimethylaminopyridine (29.7 mg, 0.243 mmol). The resulting solution mixture was stirred at rt. After 3.5 h, the reaction mixture was diluted with DCM (30 mL) and washed with 0.1N HCl (5 mL). The aqueous layer was extracted with DCM (25 mL). The combined organic layer was washed with 10% NaHCO3, brine, dried over MgSO4, filtered and concentrated. The crude material was purified by flash column chromatography (12 g, eluted with 97:3 DCM:MeOH) and dried under vacuum to give the title compound (83.2 mg, 87% yield) as a white solid. LC/MS: m/e 785.6 (M+H)+, 4.15 min (method 8). 1H NMR (400 MHz, CHLOROFORM-d) δ 4.71 (br. s., 1H), 4.59 (s, 1H), 4.48 (dd, J=10.6, 5.5 Hz, 1H), 3.89 (br. s., 1H), 3.51 (br. s., 1H), 3.40 (dd, J=13.0, 2.7 Hz, 1H), 3.27-3.21 (m, 1H), 3.20 (d, J=3.9 Hz, 1H), 2.90 (dd, J=13.1, 3.1 Hz, 1H), 2.86 (br. s., 1H), 2.74-2.60 (m, 1H), 2.53 (s, 3H), 2.51 (d, J=7.3 Hz, 2H), 2.41-2.32 (m, 1H), 2.02 (d, J=17.4 Hz, 1H), 1.86 (d, J=13.4 Hz, 1H), 1.82-1.73 (m, 2H), 1.68 (s, 3H), 1.66-1.50 (m, 7H), 1.43 (s, 11H), 1.42-1.30 (m, 6H), 1.26 (d, J=8.1 Hz, 2H), 1.23 (s, 3H), 1.22 (s, 3H), 1.12-1.04 (m, 2H), 1.01 (s, 3H), 0.95 (s, 3H), 0.84 (s, 6H), 0.83 (s, 3H), 0.78 (d, J=9.5 Hz, 1H). washed with 0.1N HCl (5 mL) The aqueous layer was extracted with DCM (25 mL) The combined organic layer was washed with 10% NaHCO3, brine dried over MgSO4 filtered concentrated The crude material was purified by flash column chromatography (12 g, eluted with 97:3 DCM:MeOH) dried under vacuum

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: To a solution of (1S,4S)-5-(2-(((1R,3aS,5aR,5bR,7aR,9S,11aR,11bR,13aR,13bR)-9-hydroxy-5a,5b,8,8,11a-pentamethyl-1-(prop-1-en-2-yl)icosahydro-1H-cyclopenta[a]chrysen-3a-yl)amino)ethyl)-2-thia-5-azabicyclo[2.2.1]heptane 2,2-dioxide (73 mg, 0.121 mmol) in DCM (2 mL) was added N,N-diisopropylethylamine (0.063 mL, 0.364 mmol), 4-(tert-butoxy)-3,3-dimethyl-4-oxobutanoic acid (49.1 mg, 0.243 mmol) (prepared as described in WO 2004014881), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (47.5 mg, 0.243 mmol) and 4-dimethylaminopyridine (29.7 mg, 0.243 mmol). The resulting solution mixture was stirred at rt. After 3.5 h, the reaction mixture was diluted with DCM (30 mL) and washed with 0.1N HCl (5 mL). The aqueous layer was extracted with DCM (25 mL). The combined organic layer was washed with 10% NaHCO3, brine, dried over MgSO4, filtered and concentrated. The crude material was purified by flash column chromatography (12 g, eluted with 97:3 DCM:MeOH) and dried under vacuum to give the title compound (83.2 mg, 87% yield) as a white solid. LC/MS: m/e 785.6 (M+H)+, 4.15 min (method 8). 1H NMR (400 MHz, CHLOROFORM-d) δ 4.71 (br. s., 1H), 4.59 (s, 1H), 4.48 (dd, J=10.6, 5.5 Hz, 1H), 3.89 (br. s., 1H), 3.51 (br. s., 1H), 3.40 (dd, J=13.0, 2.7 Hz, 1H), 3.27-3.21 (m, 1H), 3.20 (d, J=3.9 Hz, 1H), 2.90 (dd, J=13.1, 3.1 Hz, 1H), 2.86 (br. s., 1H), 2.74-2.60 (m, 1H), 2.53 (s, 3H), 2.51 (d, J=7.3 Hz, 2H), 2.41-2.32 (m, 1H), 2.02 (d, J=17.4 Hz, 1H), 1.86 (d, J=13.4 Hz, 1H), 1.82-1.73 (m, 2H), 1.68 (s, 3H), 1.66-1.50 (m, 7H), 1.43 (s, 11H), 1.42-1.30 (m, 6H), 1.26 (d, J=8.1 Hz, 2H), 1.23 (s, 3H), 1.22 (s, 3H), 1.12-1.04 (m, 2H), 1.01 (s, 3H), 0.95 (s, 3H), 0.84 (s, 6H), 0.83 (s, 3H), 0.78 (d, J=9.5 Hz, 1H). washed with 0.1N HCl (5 mL) The aqueous layer was extracted with DCM (25 mL) The combined organic layer was washed with 10% NaHCO3, brine dried over MgSO4 filtered concentrated The crude material was purified by flash column chromatography (12 g, eluted with 97:3 DCM:MeOH) dried under vacuum