methyl (2S)-3-hydroxy-2-(tritylamino)propanoate

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

Procedure: A solution of 3.6 g (13.37 mmol) of (34.2) in 15 ml of absolute THF is added to a solution of 3.72 g (10.3 mmol) of (34.3) and 3.5 g (13.34 mmol) of triphenylphosphine in 20 ml of absolute THF. 2.11 ml (13.37 mmol) of diethyl azodicarboxylate (DEAD) are added to this solution and the reaction mixture is stirred at room temperature until the reaction has come to an end. The solvent is removed in vacuo and the residue is chromatographed through silica gel using heptane/ethyl acetate. 6 g (95%) of (34.4) are obtained after concentrating the product fractions. The solvent is removed in vacuo the residue is chromatographed through silica gel

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of 10.75 g (38.56 mmol) of trityl chloride is added, at 0° C., to a solution of 6 g (38.56 mmol) of L-serine methyl ester hydrochloride and 7.8 g (77.12 mmol) of triethylamine in absolute THF and this solution is left to stir at 0° C. for 4 h and then at room temperature for 2 days. The solvent is removed in vacuo and the residue is partitioned between dichloromethane and a 10% aqueous solution of citric acid. The phases are separated and the organic phase is washed with water and dried over sodium sulfate. Following filtration, the solvent is removed in vacuo and the residue is chromatographed through silica gel using heptane/ethyl acetate=6/4. 8 g (58%) of (34.3) are obtained after concentrating the product fractions. this solution is left at room temperature for 2 days The solvent is removed in vacuo the residue is partitioned between dichloromethane The phases are separated the organic phase is washed with water dried over sodium sulfate filtration the solvent is removed in vacuo the residue is chromatographed through silica gel

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 2.8 g of trt-Ser-OMe (Bachem), 0.75 of phenol, and 2.25 g of triphenylphosphine were dissolved together in 60 ml of THF, absolute, and treated dropwise with 1.49 g of diethyl azodicarboxylate at 0° C. in the course of 30 min. The reaction mixture was stirred at 0° C. for 30 min and warmed to RT (about 1 h). For working-up, the solvent was removed under reduced pressure and the crude product was purified by chromatography on silica gel (heptane/ethyl acetate=1.5/1). The methyl (S)-2-tritylamino-3-phenoxypropionate thus obtained crystallized slowly in long needles, and was heated under reflux for 1 h in 5 M HCl to remove the protective groups. The reaction solution was evaporated to dryness under reduced pressure by coevaporating a number of times with toluene and the residue was recrystallized from a little tert-butanol. warmed to RT (about 1 h) the solvent was removed under reduced pressure the crude product was purified by chromatography on silica gel (heptane/ethyl acetate=1.5/1)

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: 2.8 g of trt-Ser-OMe (Bachem), 0.75 of phenol, and 2.25 g of triphenylphosphine were dissolved together in 60 ml of THF, absolute, and treated dropwise with 1.49 g of diethyl azodicarboxylate at 0° C. in the course of 30 min. The reaction mixture was stirred at 0° C. for 30 min and warmed to RT (about 1 h). For working-up, the solvent was removed under reduced pressure and the crude product was purified by chromatography on silica gel (heptane/ethyl acetate=1.5/1). The methyl (S)-2-tritylamino-3-phenoxypropionate thus obtained crystallized slowly in long needles, and was heated under reflux for 1 h in 5 M HCl to remove the protective groups. The reaction solution was evaporated to dryness under reduced pressure by coevaporating a number of times with toluene and the residue was recrystallized from a little tert-butanol. warmed to RT (about 1 h) the solvent was removed under reduced pressure the crude product was purified by chromatography on silica gel (heptane/ethyl acetate=1.5/1)

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

Procedure: Methyl N-trityl-L-serinate (3.61 g, 10.0 mmol), prepared by the method of Baldwin, Tetrahedron, 49, pp. 6309-6330, (1993), was dissolved in 50 mL of CH2Cl2 followed by the addition of 25 mL of 50% aqueous NaOH solution. To the stirred mixture were added benzyltrimethylammonium chloride (186 mg, 1.00 mmol) and benzyl bromide (1.20 mL, 10.0 mmol). After stirring overnight, the mixture was treated with 100 mL of ice water. After all of the ice had melted, 100 mL of CH2Cl2 was added and the layers were separated. The aqueous portion was extracted with another 50 mL of CH2Cl2 and the combined organic layers were washed with H2O (2×100 mL) and brine (3×50 mL). The organic portion was dried over Na2SO4, filtered and concentrated. Chromatography (SiO2, 10-20% ethyl acetate/hexanes) gave 3.22 g of methyl O-benzyl-N-trityl-L-serinate as a colorless syrup. the layers were separated The aqueous portion was extracted with another 50 mL of CH2Cl2 the combined organic layers were washed with H2O (2×100 mL) and brine (3×50 mL) The organic portion was dried over Na2SO4 filtered concentrated

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

Procedure: Commercially available N-trityl-L-serine methyl ester (1.60 g, 5.34 mmol) was combined with triphenylphosphine (1.28 g, 4.88 mmol) and [4-(4-hydroxyphenyl)butyl]carbamic acid benzyl ester (2.0 g, 6.68 mmol) in benzene (40 mL) at room temperature. Diisopropyl azodicarboxylate (0.958 mL, 4.86 mmol) was added dropwise and the reaction was stirred for 14 days. The solvent was removed under reduced pressure and the residue was purified by column chromatography (silica gel, eluent: 6:1, v/v dichloromethane/ethyl acetate) to provide compound 10 (2.22 g, 51%). 1H NMR (300 MHz, CDCl3) δ 7.52 (m, 6H), 7.39-7.14 (m, 14H), 7.06 (d, 2H), 6.79 (d, 2H), 5.09 (s, 2H), 4.72 (m, 1H), 4.24 (m, 1H), 4.01 (m, 1H), 3.72 (m, 1H), 3.22 (s, 3H), 3.18 (m, 2H), 2.88 (d, 1H), 2.57 (m, 2H), 1.66-1.48 (m, 4H). Rf=0.91 (5:1 v/v dichloromethane/ethyl acetate). The solvent was removed under reduced pressure the residue was purified by column chromatography (silica gel, eluent: 6:1, v/v dichloromethane/ethyl acetate)

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

Procedure: Commercially available N-trityl-L-serine methyl ester (1.60 g, 5.34 mmol) was combined with triphenylphosphine (1.28 g, 4.88 mmol) and [4-(4-hydroxyphenyl)butyl]carbamic acid benzyl ester (2.0 g, 6.68 mmol) in benzene (40 mL) at room temperature. Diisopropyl azodicarboxylate (0.958 mL, 4.86 mmol) was added dropwise and the reaction was stirred for 14 days. The solvent was removed under reduced pressure and the residue was purified by column chromatography (silica gel, eluent: 6:1, v/v dichloromethane/ethyl acetate) to provide compound 10 (2.22 g, 51%). 1H NMR (300 MHz, CDCl3) δ 7.52 (m, 6H), 7.39-7.14 (m, 14H), 7.06 (d, 2H), 6.79 (d, 2H), 5.09 (s, 2H), 4.72 (m, 1H), 4.24 (m, 1H), 4.01 (m, 1H), 3.72 (m, 1H), 3.22 (s, 3H), 3.18 (m, 2H), 2.88 (d, 1H), 2.57 (m, 2H), 1.66-1.48 (m, 4H). Rf=0.91 (5:1 v/v dichloromethane/ethyl acetate). The solvent was removed under reduced pressure the residue was purified by column chromatography (silica gel, eluent: 6:1, v/v dichloromethane/ethyl acetate)

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

Procedure: Commercially available N-trityl-L-serine methyl ester (1.60 g, 5.34 mmol) was combined with triphenylphosphine (1.28 g, 4.88 mmol) and [4-(4-hydroxyphenyl)butyl]carbamic acid benzyl ester (2.0 g, 6.68 mmol) in benzene (40 mL) at room temperature. Diisopropyl azodicarboxylate (0.958 mL, 4.86 mmol) was added dropwise and the reaction was stirred for 14 days. The solvent was removed under reduced pressure and the residue was purified by column chromatography (silica gel, eluent: 6:1, v/v dichloromethane/ethyl acetate) to provide compound 10 (2.22 g, 51%). 1H NMR (300 MHz, CDCl3) δ 7.52 (m, 6H), 7.39-7.14 (m, 14H), 7.06 (d, 2H), 6.79 (d, 2H), 5.09 (s, 2H), 4.72 (m, 1H), 4.24 (m, 1H), 4.01 (m, 1H), 3.72 (m, 1H), 3.22 (s, 3H), 3.18 (m, 2H), 2.88 (d, 1H), 2.57 (m, 2H), 1.66-1.48 (m, 4H). Rf=0.91 (5:1 v/v dichloromethane/ethyl acetate). The solvent was removed under reduced pressure the residue was purified by column chromatography (silica gel, eluent: 6:1, v/v dichloromethane/ethyl acetate)

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

Procedure: To a round-bottom flask equipped with a stir bar was added (S)-methyl 3-hydroxy-2-(tritylamino)propanoate (10.0 g, 27.7 mmol), triphenylphosphine (7.98 g, 30.4 mmol) and toluene (100 mL). The solution was stirred at room temperature for 30 min., then to the solution was added m-cresol (3.78 mL, 36.0 mmol) and diisopropylazodicarboxylate (“DIAD”, 5.92 mL, 30.4 mmol). The solution was heated at 80° C. with stirring for 18 h. The solution was cooled to room temperature and concentrated and the resulting residue was subjected to silica gel chromatography (hexanes:EtOAc) to afford (S)-methyl 3-(m-tolyloxy)-2-(tritylamino)propanoate, 8.28 g (66%). 1H-NMR (400 MHz, CDCl3) δ 7.53 (d, J=7.6 Hz, 6H), 7.29-7.23 (m, 5H), 7.21-7.11 (m, 4H), 6.77 (d, J=7.3 Hz, 1H), 6.73-6.64 (m, 2H), 5.30 (s, 2H), 4.25 (dd, J=9.3, 4.9 Hz, 1H), 4.01 (dd, J=9.2, 6.7 Hz, 1H), 3.76-3.68 (m, 1H), 3.22 (s, 3H), 2.88 (d, J=10.5 Hz, 1H), 2.32 (s, 3H). To a round-bottom flask equipped with a stir bar The solution was heated at 80° C. with stirring for 18 h The solution was cooled to room temperature concentrated

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

Procedure: To a round-bottom flask equipped with a stir bar was added (S)-methyl 3-hydroxy-2-(tritylamino)propanoate (10.0 g, 27.7 mmol), triphenylphosphine (7.98 g, 30.4 mmol) and toluene (100 mL). The solution was stirred at room temperature for 30 min., then to the solution was added m-cresol (3.78 mL, 36.0 mmol) and diisopropylazodicarboxylate (“DIAD”, 5.92 mL, 30.4 mmol). The solution was heated at 80° C. with stirring for 18 h. The solution was cooled to room temperature and concentrated and the resulting residue was subjected to silica gel chromatography (hexanes:EtOAc) to afford (S)-methyl 3-(m-tolyloxy)-2-(tritylamino)propanoate, 8.28 g (66%). 1H-NMR (400 MHz, CDCl3) δ 7.53 (d, J=7.6 Hz, 6H), 7.29-7.23 (m, 5H), 7.21-7.11 (m, 4H), 6.77 (d, J=7.3 Hz, 1H), 6.73-6.64 (m, 2H), 5.30 (s, 2H), 4.25 (dd, J=9.3, 4.9 Hz, 1H), 4.01 (dd, J=9.2, 6.7 Hz, 1H), 3.76-3.68 (m, 1H), 3.22 (s, 3H), 2.88 (d, J=10.5 Hz, 1H), 2.32 (s, 3H). To a round-bottom flask equipped with a stir bar The solution was heated at 80° C. with stirring for 18 h The solution was cooled to room temperature concentrated

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

Procedure: Methyl N-trityl-L-serinate (3.61 g, 10.0 mmol), prepared by the method of Baldwin, Tetrahedron, 49, pp. 6309-6330, (1993), was dissolved in 50 mL of CH2Cl2 followed by the addition of 25 mL of 50% aqueous NaOH solution. To the stirred mixture were added benzyltrimethylammonium chloride (186 mg, 1.00 mmol) and benzyl bromide (1.20 mL, 10.0 mmol). After stirring overnight, the mixture was treated with 100 mL of ice water. After all of the ice had melted, 100 mL of CH2Cl2 was added and the layers were separated. The aqueous portion was extracted with another 50 mL of CH2Cl2 and the combined organic layers were washed with H2O (2×100 mL) and brine (3×50 mL). The organic portion was dried over Na2SO4, filtered and concentrated. Chromatography (SiO2, 10-20% ethyl acetate/hexanes) gave 3.22 g of methyl O-benzyl-N-trityl-L-serinate as a colorless syrup. the layers were separated The aqueous portion was extracted with another 50 mL of CH2Cl2 the combined organic layers were washed with H2O (2×100 mL) and brine (3×50 mL) The organic portion was dried over Na2SO4 filtered concentrated

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

Procedure: A solution of 3.6 g (13.37 mmol) of (34.2) in 15 ml of absolute THF is added to a solution of 3.72 g (10.3 mmol) of (34.3) and 3.5 g (13.34 mmol) of triphenylphosphine in 20 ml of absolute THF. 2.11 ml (13.37 mmol) of diethyl azodicarboxylate (DEAD) are added to this solution and the reaction mixture is stirred at room temperature until the reaction has come to an end. The solvent is removed in vacuo and the residue is chromatographed through silica gel using heptane/ethyl acetate. 6 g (95%) of (34.4) are obtained after concentrating the product fractions. The solvent is removed in vacuo the residue is chromatographed through silica gel