[CH2:1]([O:8][C:9]([NH:11][CH:12]([P:16]([OH:18])[OH:17])[CH:13]([CH3:15])[CH3:14])=[O:10])[C:2]1[CH:7]=[CH:6][CH:5]=[CH:4][CH:3]=1.CC[C@@H](N)C1C=CC=CC=1>C(O)C.C(OCC)(=O)C>[CH2:1]([O:8][C:9]([NH:11][C@H:12]([P:16]([OH:17])[OH:18])[CH:13]([CH3:15])[CH3:14])=[O:10])[C:2]1[CH:3]=[CH:4][CH:5]=[CH:6][CH:7]=1A solution of 1-(benzyloxycarbonylamino)-2-methylpropylphosphonous acid (3.4 g, 12.5 mmol) in 20 mL of absolute ethanol was heated to reflux and (R)-(+)-methylbenzylamine (96% ee, 1.5 g, 12.5 mmol) was added. The resulting mixture was diluted with 120 mL of ethyl acetate. The precipitate was filtered off, washed with 100 mL of ethyl acetate and 100 mL of ether, dried in vacuo to afford (R)-1-(benzyloxycarbonylamino)-2-methylpropylphosphonous acid as a white solid (1.1 g) with a rotation [α]D=−10.87° (c=10 mg/mL 9:1 DMF-H2O). This material was found to be 93% ee by chiral HPLC.
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