| 主权项 |
1. A method comprising:
separating an S-enantiomer from an R-enantiomer wherein said S-enantiomer and said R-enantiomer are provided in a racemic mixture and wherein each of said S-enantiomer and said R-enantiomer is a compound of Formula I: wherein: R1 is C1-4 alkylene-LG wherein LG is a leaving group; R2 is hydrogen, hydroxyl, halo, cyano, C1-3 alkyl, C1-3 alkoxy, C1-3 fluoroalkyl, or C1-3 fluoroalkoxy; R3 and R4 are independently C1-3 alkyl, C7-10 aralkyl, or R3 and R4, together with the nitrogen to which they are attached, form a nitrogen-containing C4-6 aliphatic ring optionally comprising 1 further heteroatom selected from nitrogen, oxygen and sulfur; Y1 is O, S, SO, SO2 or CH2; Y2 is CH2, CH2—CH2, CH(CH3)—CH2, CH2—CH2—CH2 or CH—(CH—CH2—CH—CH2)—CH; said variable bond is above the plane for the S-enantiomer and below the plane for the R-enantiomer as illustrated respectively in Formulas I-S and I-R: dissolving one of said separated enantiomers in a suitable organic solvent; precipitating said dissolved enantiomer out of the solution obtained in step (ii) wherein said precipitating step comprises addition of water; isolating the precipitate obtained in step (iii). |
