Approaches to the total synthesis of biologically active natural products: studies directed towards bryostatins

Progress on a total synthesis of the marine natural products, the bryostatins, is reviewed. Following studies aimed at the synthesis of the 1,16- and 17,27-fragments, procedures for the assembly of the macrocyclic ring of the bryostatins were investigated. Although ring-closing metathesis was not found to be useful for the synthesis of bryostatins with geminal dimethyl groups at C18, the modified Julia reaction was found to be useful for the stereoselective formation of the 16,17-double-bond and led to a synthesis of an advanced macrocyclic intermediate. Several novel synthetic procedures feature in this work.