Synthesis
Preparation of Example 1-(R)-3-oxocyclopentanecarboxylic acid (Compound 2): 3-oxo-1-cyclopentanecarboxylic acid (Compound 1, 57 g, 445.3 mmol) was dissolved with L-leucine (193.2 g, 489.8 mmol) in water (1.036 L) and heated to reflux until the solution clarified. The reaction mixture was cooled to room temperature, the precipitated crystals were collected by filtration, washed with water and dried. The resulting crystals were recrystallized three times by passing through water (500 mL) to give (R)-3-oxocyclopentanecarboxylic acid leucine salt. The product was analyzed by chiral HPLC and the enantiomeric excess (ee) was 99.71%.
References
[1] Nucleosides, Nucleotides and Nucleic Acids, 2011, vol. 30, # 11, p. 897 - 907
[2] Patent: US2017/362235, 2017, A1. Location in patent: Paragraph 0213; 0214
[3] Bulletin of the Chemical Society of Japan, 1959, vol. 32, p. 223,224
[4] Bulletin of the Chemical Society of Japan, 1958, vol. 31, p. 333,334
[5] Chemical and Pharmaceutical Bulletin, 1963, vol. 11, p. 829 - 834
