A novel application of a Pd(0)-catalyzed nucleophilic substitution reaction to the regio- and stereoselective synthesis of lactam analogues of the epothilone natural products

Several lactam analogues of the epothilones were prepared using a concise semisynthetic approach starting with the unprotected natural products. Highlighted in this strategy is a novel regio- and stereoselective Pd(0)-catalyzed azidation reaction of a macrocyclic lactone. Subsequent reduction and macrolactamization of the resulting azide acid intermediates provided the desired macrolactams in satisfactory overall yields. The entire three-step sequence was streamlined into a "one-pot" process for the epothilone B-lactam, BMS-247550, which is currently undergoing phase I clinical trials. An initial total synthesis route to prepare the lactam analogue of epothilone C was completed and compared to the more direct semisynthesis approach. All of the lactam analogues were evaluated in vitro and the results are discussed.