Pyrazole → (αS)-α-Amino-1H-pyrazole-1-propanoic acid

Participants

Reaction Conditions

Reaction Steps

(S)-3-Amino-2-oxetanone tosylate salt (100 mg, 0.385 mmol) was added to pyrazole (131 mg, 1.93 mmol) in distilled DMF (3.0 mL) and the mixture was stirred at 25° C. for 2.5 h. The solvent was removed in vacuo at 25° C. and the residue was dissolved in H2O (3 mL) and applied to a column of BioRad AG50-X8 (trademark) (1×10 cm, H+ form) The resin was washed with H2O (30 mL) and eluted with a gradient of aqueous NH4OH (0 to 0.25N over 70 mL, then 100 mL of 0.25N NH4OH). The product emerged chromatographically pure with 0.25N NH4OH and was lyophilized (2×) and dried in vacuo over P2O5 to yield 77% (46.2 mg) of β-(pyrazol-1-yl)-L-alanine (mp 234°-236° C. (dec)). For an improved melting point this material could be recrystallized from H2O/ EtOH: mp 241°-243° C. (lit. mp 236°-238° C. (dec), 243° C. (dec)); [α]D25 -72(±1) (c 0.54, H2O) (lit. [α]D -78° (c 3.4, H2O),-72.0° (c 1. H2O)); IR (KBr disk) 3700-2200 (m, vbr), 1617 (s), 1580 (s), 1485 (m), 1395 (m), 767 (m) cm-1 ; 1H NMR (300 MHz, D2O)δ 7.65 (d, 1H, 2 Hz, ArHH'H"), 7.61 (d, 1H, 2 Hz, ArHH'H"), 6.38 (t, 1H, 2 Hz, ArHH'H"), 4.66 (d, 2H, 5 Hz, CH2N), 4.18 (t, 1H, 5 Hz, CH); POSFAB-MS glycerol/HC1 ) 156 (MH+), 311 (M2H+); Rf 0.67 (Solvent A; characteristic blue-purple color with ninhydrin).

Provenance & Evidence