(-)-Mandelic acid → (-)-7-Amino-5-benzyl-7-methyl-5-azaspiro[2.4]heptane d-mandelate

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Reaction Steps

D-Mandelic acid (111 g) was added to a solution of 7-amino-5-benzyl-7-methyl-5-azaspiro[2.4]heptane (325 g, purity: 81.3%, 1.22 mol) in toluene (4.8 L), and seed crystals for the title compound were added to the mixture, followed by stirring overnight (for 20 hours) at an internal temperature of −9° C. The precipitated crystals were collected through filtration, followed by washing twice with cold toluene (400 mL) and drying under reduced pressure, to thereby yield the title product as white crystals (117 g, yield: 26.0%, optical purity: 99.2% e.e.). Optical purity of the product was determined through HPLC. Specifically, the mandelate (about 10 mg) was sampled, and 10% aqueous sodium hydroxide (0.3 mL) and hexane (0.3 mL) were added to the sampled mandelate. After stirring, the mixture was left to stand, and the hexane layer was analyzed through HPLC. The 1H-NMR spectral data given below were obtained from the free form of the product.

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