The general procedure for the synthesis of (R)-1-(((9H-fluoren-9-yl)methoxy)carbonyl)piperidine-2-carboxylic acid from the compound (CAS: 102774-86-7) and L-2-piperidinic acid is as follows:
1. L-piperidine acid (3.6 g, 38.7 mmol) was dissolved in 40 mL of 10% aqueous sodium carbonate solution in a round-bottomed flask and stirred at room temperature for 5 min.
2. Fmoc-OSu (8.5 g, 34.8 mmol) dissolved in 35 mL of dioxane was added to the above solution and the reaction mixture was stirred overnight.
3. After completion of the reaction, water was added and the aqueous layer was extracted with ethyl acetate.
4. The aqueous layer was adjusted to pH=2 by adding concentrated hydrochloric acid and then extracted with ethyl acetate (3 x 40 mL).
5. The organic phases were combined, washed sequentially with 1N hydrochloric acid and saturated brine, dried with anhydrous magnesium sulfate, and concentrated under reduced pressure to obtain a colorless oily liquid.
6. The oily liquid was dissolved in ether, cooled and precipitated as a fluffy white solid, washed with hexane and dried to afford (S)-1-(((9H-fluoren-9-yl)methoxy)carbonyl)piperidine-2-carboxylic acid (8.2 g, 38.7 mmol, 83% yield).
Product Characterization Data:
- TLC (unfolding agent: hexane:EtOAc:TFA = 1:1:0.2): rf = 0.60
- HPLC (gradient A): retention time = 24.6-24.8 min
- 1H NMR (300 MHz, CDCl3): δ 1.28-1.53 (m, 2H), 1.69-1.82 (m, 3H), 2.19-2.37 (m, 1H), 3.15 (t, 1H, J = 13.2 Hz), 4.05-4.33 (m, 2H), 4.37-4.49 (m, 2H), 4.76- 5.05 (m, 1H), 7.28-7.41 (m, 4H), 7.55-7.62 (m, 2H), 1.77 (s, 2H)
- 13C NMR (75 MHz, CDCl3): δ 20.72, 24.70, 26.55, 41.94, 47.25, 54.19, 67.86, 119.97, 125.08, 127.07, 127.68, 141.33, 143.89, 156.65, 177.36
- MS (ESI): m/z 352.66 [M + H]+, calculated 352.40 [M + H]+
