Methanol → HCID 15907893, compound
Reaction equation
[CH3:1][C:2]1[CH:3]=[C:4]([CH:21]=[C:22]([CH3:24])[CH:23]=1)[NH:5][C:6]([CH2:8][C:9]1[CH:20]=[CH:19][C:12]([O:13][CH:14]([CH3:18])[C:15]([OH:17])=[O:16])=[CH:11][CH:10]=1)=[O:7].[CH3:25]O>C(O)C>[CH3:24][C:22]1[CH:21]=[C:4]([CH:3]=[C:2]([CH3:1])[CH:23]=1)[NH:5][C:6]([CH2:8][C:9]1[CH:10]=[CH:11][C:12]([O:13][CH:14]([CH2:18][CH3:25])[C:15]([OH:17])=[O:16])=[CH:19][CH:20]=1)=[O:7]Participants
4
Reactant 2
Product 1
Reagents, catalysts & solvents 1
Procedure
The mother liquor from the recrystallization of (−)20-cinchonidine salt was concentrated under reduced pressure. The enriched (+)20 isomer was obtained from the mother liquor by neutralizing the salt to obtain the free acid, as described previously for compound 18. The optical rotation showed that the isomer was approximately 80% enantiomeric excess, optical rotation was measured at 21° C.: [α]D+18.2° (c=1.2, methanol). A stock solution (1 mg/mL) of the racemic mixture (20) was prepared in ethanol/mobile phase (1:1). The injected sample volume was 250 μL. The compound was eluted with a mobile phase of heptane/ethanol. with 1% TFA (88:12) at a flow rate of 2.5 mL/min. Under these conditions, the (−)isomer eluted at 15.8 min and the (+)isomer eluted at 18.2 min retention times. The collected fractions were concentrated under reduced pressure at room temperature. (+)20 was collected as a white solid, 0.14 g. mp 146-148° C. The optical rotation was measured at 21° C.: [α]D+25.3° (c=0.5, methanol).