Results The racemic AP N-acetylcysteamine derivative 9, with two 13C labels spanning the acetate-propionate junction, was synthesized as shown in Scheme 11. In our initial approach, ethyl [2, 3-'3C2] acetoacetate (61, synthesized from [l-13C] acetyl chloride and monopotassium [2-13C] ethylmalonate, was methylated in 95% yield via the thallium enolate? Although the ester 7 could be readily hydrolyzed with aqueous alkali, the free ...
