Oxalic acid dihydrate → HCID 70191891, compound

Participants

Reaction Steps

(5S,1'S)-3-phenylmethyl-5-(1'-tert-butoxycarbonylamino-2'-phenylethyl)-2-isoxazoline (2.0 g, 5.26 mmol) was dissolved in an ammonia/methanol solution (3%, 20 ml). A 3% Pt-on-carbon catalyst (100 mg, 5% by weight based on substrate) was added thereto. The mixture was stirred for 21 hours in a hydrogen atmosphere at atmospheric pressure. The catalyst was removed by filtration under reduced pressure, and then the filtrate was concentrated under reduced pressure. A foamy residue (2.0 g) containing (2S,3S,5S)-2-tert-butoxycarbonylamino-3-hydroxy-5-amino-1,6-diphenylhexane and (2S,3S,5R)-2-tert-butoxycarbonylamino-3-hydroxy-5-amino-1,6-diphenylhexane was obtained. By the HPLC analysis of the residue (absolute calibration curve method) using CHIRALPAK AD (trade name), 1.47 g of (2S,3S,5S)-2-tert-butoxycarbonylamino-3-hydroxy-5-amino-1,6-diphenylhexane (yield: 73%) and 0.28 g of (2S,3S,5R)-2-tert-butoxycarbonylamino-3-hydroxy-5-amino-1,6-diphenylhexane (reaction yield: 14%) were contained. Oxalic acid dihydrate (633 mg, 5.26 mmol) was added to the residue, the mixture was heated to dissolved in aqueous methanol (water content: 20% v/v, 22 ml). When the mixture was dissolved, it was cooled and crystals precipitated were collected by filtration. The crystals were washed with aqueous methanol (water content: 20%) and dried under reduced pressure to give colorless crystals. By HPLC analysis of the crystals, (2S,3S,5S)-2-tert-butoxycarbonylamino-3-hydroxy-5-amino-1,6-diphenylhexane and (2S,3S,5R)-2-tert-butoxycarbonylamino-3-hydroxy-5-amino-1,6-diphenylhexane were contained in the ratio of 97:3. Part of the crystals were further recrystallized with aqueous methanol (water content: 20%) to give the pure desired compound in crystals, which were confirmed, by HPLC, not to contain (2S,3S,5R)-2-tert-butoxycarbonylamino-3-hydroxy-5-amino-1,6-diphenylhexane.

Provenance & Evidence