AbstractAcetonyldethio coenzyme A (1) together with its 2′‐phospho isomer10was obtained by the following reaction sequence: coupling of the glycol ketal4of 5‐amino‐2‐pentanone withN‐benzyloxycarbonyl‐β‐alanine, fusion of the deblocked aletheine analog5with the lactone of D‐2,4‐dihydroxy‐3,3‐dimethylbutyric acid to yield the pantetheine analog6, which was phosphorylated at the 4′‐hydroxy group to form7, and then condensation with adenosine 2′,3′‐cyclic phosphate 5′‐phosphoric morpholide. The isomeric mixture exhibited strong competitive inhibition of citrate synthase (S‐acetyl