Analytical Reference Standards: Synthesis and Characterization of ±-threo-Ritalinic Acid-D10 Hydrochloride
Authors: Elizabeth B. Marek PhD, Huahua Jian PhD, Uma Sreenivasan PhD, Isil Dilek PhD
Presented at Society of Forensic Toxicologists (SOFT) / The International Association of Forensic Toxicologists (TIAFT), San Francisco, CA, September 2011
Abstract
As a major metabolite of methylphenidate (1, Ritalin) ±-threo-Ritalinic acid (2) is of clinical relevance. To this end ±-threo-ritalinic acid-D10 HCI (3) was synthesized in seven steps with a purity of 99% and an isotopic purity ratio of D0/D10 = 0% and a significant amount of the D9-D7 isomers. Because practical ion monitoring is based on the ratio of D0/D10, the standard was found to be suitable for use as an internal standard in LC-MS/MS analysis of ritalinic acid and related compounds. The presence of significant amounts of the D9 isomer prompted extensive structure elucidation work using 1D, 2D, and qNMR techniques.