Among the thousands of cytochrome P450 enzymes known, many selectively hydroxylate the hydrocarbon tail of fatty acids at the terminal (v) position and the v-1, v-2, and v-3 positions. A general method for synthesis of (v-2, v-2, v-3, v-3)-tetradeuterio-fatty acids that can be used in mechanistic studies of cytochromes P450 is illustrated by the synthesis of 9, 9, 10, 10-tetradueteriododecanoic (lauric) acid and 13, 13, 14, 14- ...