New solid-phase catalysts for asymmetric synthesis: cross-linked

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J. Org. Chem. 1990,55, 304-310

trated to 20 mL. Toluene (20 mL) and 5% aqueous acetic acid (20 mL) were added to the concentrate. The phases were well mixed and then separated. The toluene layer was washed with 5% aqueous acetic acid (20 mL). The combined aqueous layers were washed with toluene (10 mL). The aqueous layer was fdtered and the insolubles were redissolved by washing the filter with 5% aqueous acetic acid (40 mL). The combined filtrates were concentrated to 40 mL to remove dissolved toluene. The product as the acetate salt crystallized from solution. Water (50 mL) and acetic acid (8.5 mL) were added to the concentrate and the mixture was heated at 45 OC to redissolve the solids. The clear solution was cooled to 20 "C and concentrated ammonium hydroxide (25 mL) was added with stirring at