(-)-(1S,4R)-N-BOC-4-AMINOCYCLOPENT-2-ENECARBOXYLIC ACID

beige to light brown crystalline powder

peptide synthesis

To a (1R,4S)-2-azabicyclo[2.2.1]hept-5-en-3-one (5.0 g, 46 mmol)/water (30.5 ml) solution of Aqueous HCl solution (2M, 23.0 ml, 46.0 mmol) was added to the solution. The reaction mixture was heated at about 80 C for about 2 h to . After heating at about 80 C for about 2 h to , the reaction mixture was cooled to ambient temperature and the solvent was removed under reduced pressure. The solid was dried in a vacuum oven at about 70 C and used without further purification. The solvent was added to (1S,4R)-4-amino at about 0C. The solvent was removed under pressure. (1S,4R)-4-amino -cyclopent-2-enecarboxylic acid hydrochloride (9.20 g, 45.8 mmol)/1,4-dioxane (15 ml) and water (18.3 ml). (18.3 ml) solution was added DIEA (32.0 ml, 183 mmol). After stirring for about 5 minutes, di-tert-butyl bicarbonate (di-tert-butyl ) was added. dicarbonate) (11.7 ml, 50.4 mmol)/1,4-dioxane hexane (5 ml) solution. The reaction mixture was brought to ambient temperature and stirred for about 18 hours. The solvent was removed under reduced pressure and the crude oil was dried in a vacuum oven at about 65C for about 3 hours. The crude oil was extracted with A gradient elution of 80-100% EtOAc/heptane purified the crude product by silica gel chromatography to afford (-)-(1S,4R)-N-tert-butyloxycarbonyl-4-aminocyclopent-2-ene-1-carboxylic acid (5.2 g, 50%, two steps): LC/MS (Table 2, method a) Rt = 1.81 min; MS m/z: 226(M-H)-.