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A strategy for expanding the linear working range in bioanalysis using quantitative high performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS) is presented. The strategy involves monitoring multiple product ions. Herein we demonstrate the strategy on a rat plasma assay for a proprietary experimental drug where the linear range is expanded from 2 to 4 orders of magnitude. A primary sensitive ion was monitored to obtain a high sensitivity range calibration curve (0.400 to 100 ng/mL) while a less sensitive secondary ion was monitored to obtain a low sensitivity range calibration curve (90.0 to 4000 ng/mL). Each calibration curve gave acceptable linearity (r >0.990). Quality control samples at low, mid and high levels within each calibration curve demonstrated acceptable precision and accuracy (within 20% for all levels). The technique was successfully applied to rat pre-clinical sample analysis.

Attempted imine formation between 3-hydroxycamphor and tert. butyl glycinate led to 8 the substitution product at the 3-position. Zinc-acetic acid treatment of 8 afforded 3-acetoxycamphor. Alkylation of the imine from from norcamphor and tert. butyl glycinate gave no stereoselection. Alkylation of the imine from from 10-hytdroxymethylcamphor and tert. butyl glycinate gave stereoselectivities inferior to those obtained from the imine of camphor itself ( 1 ) but aldol condensation with benzaldehyde, a reaction not possible with 1, was affected in 71% yield.