We recently reported1 a chromatographic resolution for synthetic precursors of carnitine (5) and 4-methylcarnitine (6), although at that time the absolute configurations of 6 were not assigned. NMR has been increasingly used for such assignments (see ref 2 for a review), and it became apparent that the NMR method of Trost3for determining the absolute configuration of secondary alcohols as their O-methylmandelate esters might be applicable in these systems. Here we report the success of Trost’s model for predicting the known configurations of carnitine enantiomers and describe a simple XH NMR method for establishing the absolute configurations for the two asymmetric centers in the four stereoisomers of 4-methylcarnitine. © 1988, American Chemical Society. All rights reserved.