Triacetoxyperiodinane → tert-butyl N-((2S)-1-oxopropan-2-yl)carbamate

(S)-(−)-2-(tert-Butoxycarbonylamino)-1-propanol (523 mg, 2.98 mmol, 1.0 equiv.) was dissolved in 45 mL methylene chloride in a 100 mL r.b. flask with a magnetic stir bar. To this clear homogeneous solution, Dess-Martin periodinane (1.523 g, 3.591 mmol, 1.2 equiv.) was added in one part and the cloudy white reaction mixture was allowed to stir at room temperature for 2 h. Thin-layer chromotography monitored the reaction to completion. The reaction mixture was diluted with 100 mL ethyl acetate. Sodium bisulfite solution (2 M, 20 mL) was added to the reaction mixture and the organic layer was separated. The aqueous layer was washed with 3×30 mL EtOAc. The combined organic layers were washed with 50 mL 1 M NaOH, followed by saturated NaCl (30 mL) and dried over MgSO4. Filtration and rotary evaporation produced the desired product as a yellow oil (475 mg, 92% yield, Rf=0.63, 1:1 hexanes/ethyl acetate). Step B: Preparation of [2-(4-methoxy-phenylamino)-(1S)-methyl-ethyl]-carbamic acid tert-butyl ester. (S)-2-(tert-Butoxycarbonylamino)-propionaldehyde (473 mg, 2.74 mmol) and p-anisidine (1.031 g, 8.371 mmol, 3.0 equiv.) was dissolved in 45 mL of MeOH at 0° C. in a 100 mL r.b. flask with a magnetic stir bar. Optionally, acetic acid (469 μL, 8.21 mmol, 3.0 equiv.) can be added via syringe to assist in the reaction. To the stirring dark colored solution was added sodium cyanoborohydride (326 mg, 5.82 mmol, 1.89 equiv.). Gas evolution and disappearance of color were observed. The reaction was allowed to slowly warm to room temperature with stirring over 30 minutes and the reaction was monitored by LC/MS. At the completion of the reaction, the mixture was quenched with 1 M NaOH, and extracted 3×50 mL ethyl acetate. The resulting organics were washed with 50 mL saturated NaHCO3, 40 mL saturated NaCl, and dried over MgSO4. Evaporation of ethyl acetate provided 728 mg of a brown oil. Purification by automated ISCO chromatography provided a clear oil of [2-(4-methoxy-phenylamino)-(1S)-methyl-ethyl]-carbamic acid tert-butyl ester (583 mg, 2.079 mmol, 76% yield). HPLC-MS calcd. for C15H24N2O3 (M+H+) 281.2. found 281.5. 1H NMR (CDCl3, 400 MHz) δ 1.21 (d, 6H, J=6.6 Hz), 1.47 (s, 9H), 3.05 (dd, 1H, J=12.2, 7.3 Hz), 3.13 (dd, 1H, J=12.2, 4.6 Hz), 3.76 (s, 3H), 3.93 (broad s, 1H), 4.62 (broad s, 1H), 6.60 (d, 2H, J=6.8 Hz), 6.80 (2H, d, J=6.8 Hz). Step C: [2-(4-Methoxy-phenylamino)-(1S)-methyl-ethyl]-carbamic acid tert-butyl ester (383 mg, 1.37 mmol) was added to 10 mL of a trifluroacetic acid solution (10 v/v % in methylene chloride) at room temperature in a 25 mL r.b. flask with a magnetic stirbar. The reaction turns dark purple/black in color after 5 minutes. The reaction is allowed to stir at room temperature until the reaction is judged complete by HPLC/MS. The solvent is removed by evaporation and to provide 2-(4-Methoxy-phenylamino)-(1S)-methyl-ethyl-ammonium trifluoroacetate salt as a brown oil (394 mg, 1.34 mmol, 98% yield) and used directly in the next reaction. HPLC-MS calcd. for C10H16N2O (M+H+) 181.1. found 181.5.

1. customthe reaction to completion
2. customthe organic layer was separated
3. washThe aqueous layer was washed with 3×30 mL EtOAc
4. washThe combined organic layers were washed with 50 mL 1 M NaOH
5. dry with materialdried over MgSO4
6. filtrationFiltration and rotary evaporation

ORD-Eintrag

ord-4e4b8f7bb03948a1930aef1748e794f4

Quelldatensatz

uspto-grants-2007_02

DOI

10.6084/m9.figshare.5104873.v1

Patentnummer

US07173051B2