Normal-phase chiral liquid chromatography-mass spectrometry of non-UV-active compounds: applications for pharmaceutically relevant racemates.
Mixtures of hexane-like ethoxynonafluorobutane with alcohols were used as MS-friendly mobile phases for separation and efficient detection of non-UV-active enantiomers and diastereomers using normal-phase HPLC-APCI-MS. Racemic muscone, camphorsulfonamide, camphorsultam, BOC-protected 1-(3-aminopropyl)-2-pipecoline and diastereomeric 2-methylhexanoyl camphorsultams were resolved on Chiralpak AS and AD and achiral Luna CN columns. The responses of UV and APCI-MS detectors were compared under separation conditions studied, with MS detection achieving lowest detectable quantity in the range of 0.5-2 ng per chromatographic peak. The absolute configuration of crystalline derivatives of racemic 2-methylhexanoic acid with (S)-(-)-2,10-camphorsultam was determined by X-ray analysis after their automatic purification by preparative LC-MS. The technique described can be used to purify and determine the absolute stereochemistry of compounds of unknown structure which contain free carboxy group and lack sufficient UV absorbance.
Kagan
M
M
Discovery Analytical Chemistry, Chemical Sciences, Wyeth Research, CN 8000, Princeton, NJ 08540, USA. kaganm@wyeth.com
Chlenov
M
M
Greenfield
A
A
Ho
D M
DM
D002073:Butanes / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D003516:Cycloparaffins / Q000737:chemistry / Q000302:isolation & purification; D006845:Hydrocarbons, Fluorinated / Q000737:chemistry; D015394:Molecular Structure; D004364:Pharmaceutical Preparations / Q000737:chemistry / Q000302:isolation & purification*; D015203:Reproducibility of Results; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013237:Stereoisomerism; D014466:Ultraviolet Rays; D005466:Fluorocarbons
D002073:Butanes; D003516:Cycloparaffins; D006845:Hydrocarbons, Fluorinated; D004364:Pharmaceutical Preparations; C438669:ethoxynonafluorobutane; D005466:Fluorocarbons; C031021:muscone