transformed gradually into needle like crystals after stirring furthermore at 40 u00b0 c for 60 min the solution was cooled to 25 u00b0 c at a rate of approximately 0 5 u00b0 c per minute after stirring at 25 u00b0 c for 60 min the separated crystals were collected by filtration and washed with methyl acetate containing water at 4 vol 30 ml to afford the desired crystal c 23 74 g purity 98 5 in a 79 7 n n yield b to 2 u2032 cyano 2 u2032 deoxy n 4 palmitoyl 1 u03b2 d arabinofuranosylcytosine 60 g which is the compound described in example 1 1d of the japanese patent no 2569251 or u s pat no 5 691 319 was added methyl acetate containing water at 2 5 vol 600 ml and the resulting mixture was stirred at about 23 u00b0 c for 2 hr and then cooled to 12 u00b0 c at a rate of approximately 0 5 u00b0 c per minute after stirring at 12 u00b0 c for 1 hr the separated crystals were collected by filtration washed with methyl acetate containing water at 2 5 vol 180 ml and dried to afford the desired crystal c 55 1 g purity 94 5 in a 89 6 n n yield 1 the dried crystal c was kept standing for about 20 min under an atmosphere moistened to more than 45 humidity to afford the desired crystal c i 2 to the dried crystal c was added water to an amount which corresponds to about 33.