Synthesis and carbon-11 labeling of the stereoisomers of meta -hydroxyephedrine (HED) and meta -hydroxypseudoephedrine (HPED)

Abstract

The synthesis of the four stereoisomers of carbon-11 labeled meta -hydroxyephedrine (HED) and meta -hydroxypseudoephedrine (HPED) was undertaken for evaluation of their in vivo kinetic behavior. The stereoisomers of HED and HPED were synthesized by conversion of their respective enantiomerically-pure, normethyl precursors ( meta -hydroxyphenylpropanolamine stereoisomers) to the carbamate derivatives and subsequent reduction with lithium aluminum hydride. Direct N -[ 11 C]methylation of the appropriate normethyl precursor with [ 11 C]methyl triflate and HPLC purification provided the radiotracers in 27–42% (average = 36%; n = 12) decay-corrected radiochemical yields in a 40 min synthesis time from end-of-bombardment. The specific activity of the radiotracers was 1260–1625 Ci/mmol (average = 1368 Ci/mmol; n = 8) at end-of-synthesis and the radiochemical purity >98%. Copyright © 2000 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34875/1/345_ftp.pd